sae_mem_14.pdf

Computer Audio Playback & Stereo USB DACs

JFVignal 1 SAE Br-ussels-AEDS 90812010

__ ~ontents

--- 1. Summary 003 2. Background & tvLlajor Trends 006 3. Computer-base Audio 014 4. Digital 1 nterfaces 022 S. S/Pd if Topologies 038 6. S/Pdif Oversampling & Reclocking 054 7. USB vs FireWire 069 8. USB Ad apt ive vs A ync 088 9. Ethernet 097 1 O. From PCM To DSD 1 1 1 1 1 . Selection of Stereo DACs 122 12. Conclusion 52 13. References & Prefere11ces 1 55 14. Sources & Resources 1 8

JFVignal 1 SAE Brussels-AE S 90812010 2

1

--1 nis paper is about mus· uction at home, not music production perse.

• The tt:aditi a set-up of a typical Hi Fi system, with the CD player as the main playback source, is being redefined by new products & technologies from different industries (Pro Audio, High End Audio, Computer, Consumer electronics), ali merging into the global Digital Convergence.

• Today, options for copying, downloading, storing music & managing an audio library have multiplied, as weil as options for playback & listening.

• Music servers & digital jukeboxes, from iPod to PC, push consumers into file-based audio management, as opposed to physical-format-based audio playback.

• The 30-year old Red Book CD has been simply dematerialized. • One key benefit is the ability to download & listen to high-resolution files. • One key challenge is the ability of the end-user to manage this new complexity,

with so many variables both at the software & hardware levels. • ln particular, typical audio interfaces like AES/EBU and S/Pdif are now competing

against computer interfaces like USB, FireWire & Ethernet. • Because digital playback requires in any case a Digital To Analog converter

(DAC), more & more manufacturers are now launching USB DACs. • The purpose of this paper is to give an overview of this huge shift happening

today & to focus on the different designs used in USB DACs, a Iso including other options like S/Pdif, FireWire, Ethernet & music servers.

JFVignal 1 SAE Brussels-AEDS 90812010 4

• My primary objective for this paper was to adjust scope & depth with clarity & relevance, the right mix for a primer (this is not a white paper).

• One issue was to balance the amount of specifie info on the topic vs more technical background data needed for reference.

• Key points for each topic & section summaries are highlighted. • More in-depth technical information is readily available from the URL

sources & resources listed at the end (ali val id URLs as of April 201 0). • Because the computer-audio market is currently booming, more products

(both hardware & software) are being released from Pro audio & Hi end manufacturers. Specs are fast-evolving as weil as retail priees.

• USB right now is the most popular in terms of cost/performance ratio, but FireWire is still a live & Ethernet is positioning itself as the new alternative.

• Part of the background for this paper a Iso co mes from my own experience in creating & managing an audio library of more than 4,000 CDs over the last 5 years. Mistakes were made, insights were gained.

• Another persona! learning curve has been the optimization of the computer (custom desktop on W03/W7 and Mac Book Pro OSX 1 0.5.8) as the playback source within an existing home audio system, especially in terms of DAC interface. Efforts at improving the system overall are still ongoing.

J F Vignal/ SAE Brussels-AEDS 908 1 20 1 0 5

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JFVignal/ SAE Brussels-AEDS 908/2010 6

~

0

) • Traditional CD playback= integrated CD player or CD transport + outboard DAC, with S/Pd if or AES/EBU connection.

• Impact of 1-Pod (200 1 ), 1-Tunes (2003) & 1-Pod docks. • Trivialization of music due to low-quality mp3, the hit single syndrome, radio

heavy compression, P2P downloads. • Today, new market for computer-based audio (digital jukebox). • Computer Audio= using a computer as the transport for music playback. • This strong trend in digital convergence brings together Pro Audio (production),

Hi-Fi (re-production) and computers (storage, playback). • The PC becomes a music player (drive), music library & music server. • As a result, new market for outboard DACs for connection to PC. • Which digital connections (S/Pdif, AES3, Toslink, USB, FireWire, Ethernet) ? • DACs with USB/FW, no need for soundcard PCI-PCie or outboard interface. • CD, SACD, DVD-A dying physical formats (dematerialization). • Blu-Ray (BD) as the new playback platform ? (eg., NeiiYoung'sArchives) • New market for high-res audio files downloads, PCM 24/96 to 24/192, DSD and

DXD downloads (eg., Norwegian music label 2L). • Cheaper costs of storage with HDDs, SSDs capacity increasing.

JFVignal/ SAE Brussels-AEDS 908/ 2010 7

• CD sales down by +/- 1 0% every year. • Legal music downloads up by +/- 30% every year. • Hi end audio manufacturers strong focus on DACs & music servers. • Linn stops manufacturing CD players & transports, as of Dec 2009. • Vinyl: From survival to revival ( 180g vinyl re issues) © • Internet radio streaming & music discovery sites (Deezer, Last.fm, Spotify ... ). • Today audio is increasingly played back from computers, streaming network

players and hard disk players. • TVs, gaming consoles and portable audio players can also be interconnected via

routers/servers. • Computer platforms & OS market shares:

0 Windows: 90% 0 Apple: OSX 5% 0 Linux: 5%

• OS cross-installation solutions: Windows <=> OSX (Boot Camp, Parallel Desktops,VM Ware).

• Today we take ali the above for granted. • Over the last 50 years, audio & Hi Fi have come a long way.

J F Vignal 1 SAE Brussels-AEDS 908 1 201 0 8

Technology and the Growth of Audio Markets

Sound ~ac ic es magazine Misan& PlY Revival

~ Ub·FiHobbyi.rts i1 ]3pan &Itty l tJ:Jm. Fi Tm de

opMe~t Ster e SoJ.,f1d, Audio ~ esearch, S. !J" epan, Krell, P..poge ~~ l evins lnfir 1y & àhet'$

Sec t, Stere Tape,

1 ,J High- End Audio

Fish ~; Rec œds, Ma ra z, & M Dolby, THX

Ampe> etc . ( ISS 5-63] certification

v7{ High Fidelity ' Home Theater

Mv Ra do f!.i,~/FMIPh DolbyCa::.sett es,

.A.C-3,DTS no

\ 44. 1116 Di gtal CD,

&E ectrical 1 F umihr e Con oies & Rack Sereo 9&'24, D\oO -A Phor o!}'aph$ p..Ç/DC Tat:Ae iadios

1

SPCD ~ R ec ei V et'$

htfa ss J:vf.arket (Priee, Ji:>pearance, & Features)

• \ Sound Or.tical GraduaJ T ec rt1ic ol cr, Otality ~olby ~olby 5.1 Crennel on Dise Sound Retinemert Cinerama, Decline; ereo ~.rround, Compressed

211 2A3, & 71Xnm,& 71Xnm Jiical THX, ~igital Tri ode 3008 Earl y 6-track & Sta"eO ou nd 71Xnm, ystems

&6l6 Stereo Ma(Tleijc fades oti ~ .. &IMP.X

1 :tvfovie Theater Sound

1920 1930 1940 1950 1960 1970 1980 1990 2000

Source: http://www.nutshellhifi.com/library/tinyhistoryl.html


Jvfilestones ln Audio

1 8 Tre.ck Il Prere<:orded Doby 8 cassette

1

1 Open-Reet Ste'eo Tape 1 ~ 1

44.1 kHz/16 bit CD

1 1

45 Singt&s , _______ ----- 95124 DVD-A [

1 1

.é.COLSttal 1 E le<:trta 1 7 8 Recorœ 1 Mooo LPI Stereo LP Recorœ ---~ 1 1 J

I.Atmstron g~ FM 1 88-1 Ollv1hz FM 1 88-1 Otrv1hz FM Stereo

1 1 1

Broadcast and Sr.ortwave AM Radio

j_ RCA [3 RCA RCA Small 741 Fast LP&

26 6SN7 12AU7 Signal 301 .A.udio Triode 6

r 6SL7 12AX7 Transsta Opamp3 Opamp3 R€'Yivat

RCA RCA EL341KT88 Quasi- Comp. LOYY True DHT 71,4S,2A3 6V6 More Feedback Comp . Symm. Tlh-1 cass Triode WE 3008 6L6 tv1ore POVv'er Trans . Trans. Less FB A R€'Yival

1 1 Voght Al tee ... IBL rE AR

BBC Computers, Higher Tractrix 604 Klpscr KLH LSJl5A Potyprop EfftierK:y

Horn Dt.plex iranooy IAdvent Bextrene Kevlar

1920 l930 l940 1950 1960 1970 1980 1990 2000 High- Fidelity Transition Stereophonie

----------------------~-~----~~·~ ~------------~------------------~ Ra.dio & IYhvies

JF Vignal/ SAE Brussels-AEDS 908/2010 10

0 Digital Timeline

• 1841 • 1928 • 1937 • 1948

• 1958 • 1960

• 1967

• 1969

• 1977 • 1980 • 1982 • 1987 • 1994

• 1999

• 2000

• 2001

Augustin-Louis Cauchy first proposed sampling theory. Harry Nyquist presents sampling theory to the American lnstitute of Electrical Engineers. Reeves proposed pulse code wave modulation (PCM) as a way of storing audio. John Bardeen,William Shockley and Walter Brattain's bi polar junction transistor, which made compact digital circuitry a reality. C.H. Townes and A.L. Shawlow invented the laser. I.S. Reed and G. Solomon's work on error correction codes gave us the technology that would be directly applied to Compact Dise twenty two years later. Japan's NHK Technical Research lnstitute publicly demonstrates a digital audio recorder running 12bit resolution and a 30kHz sampling rate. Physicist Klaas Compaan uses a glass dise to store black and white holographie images using frequency modulation at Philips Laboratories. Sony, Mitsubishi and Hitachi demonstrate digital audio dises . Sony signs up to Philips 'Red Book' laser dise. Compact Dise is born. Sony and Philips launch first commercial CD players. Sony launches Digital Audio Tape (DAT) with 16bit, 48kHz digital PCM system. MP3 (MPEG 1 Audio Layer 3) finalized. A compressed, lassy 16/44.1 format using approximately 20% of the space of a WAV file, it ushers in online music distribution. Super Audio Compact Dise (SACD) launched, offering high resolution digital sound using the Direct Stream Digital (DSD) system, with effective 20-bit resolution. DVD-Audio is launched from the DVD-Forum; offering up to 24bit, 96kHz resolution from a DVD. The format dies from competition with SACD & lack of distribution support. Josh Coulson finalizes Free Lossless Audio Codee (FLAC) v 1.0.

Source: http://blog.bowers-wilkins.com/lab/sound-quality-lab/the-definitive-guide-to-24-bit-flac/

JFVignal 1 SAE Brussels-AEDS 90812010 Il

ormats, Med1a & Playback

1> LP 2> CD

(0 - .1

3> HDD 4> SSD JFVignal/ SAE Brussels-AEDS 908/ 2010 12

• W e are now living in the age of computer audio playback. • Audio companies are offering stereo DA converters, either in USB (from cheap

plug & play boxes to more elaborate deviees with custom drivers) or FireWire, Ethernet being still a more limited & costly option.

• Laptops & Mac Minis w ill obviously favor the USB alternative. • For a desktop, the option remains to instal a Pro-audio PCI/e soundcard to keep

a digital output in S/Pdif and AES3, which can then be transferred to an outboard stereo DAC.

• End-users, depending on budget & performance objectives, can therefore choose from severa! computer-audio configuration strategies.

• ln any case, computer audio files can now be played on a home Hi Fi setup with a quality level unheard of as recently as two years ago.

• Jitter management remains a core issue to deal with, and cornes from a number of different sources in the ove rail playback chain.

• One potential jitter suspect was the laser-based optical playback of CD players: by shifting from CD to HDD (ferromagnetic) or SSD (solid-state memory) playback, a more stable source can be established.

JFVignal 1 SAE Brussels-AEDS 908 1 2010 13

0


0

0 Computer Audio & Clocking

• Over the last 5 years, PCs for digital playback have been gaining popularity, due to increasing CPU power, lower cost of storage & music libraries.

• lt is quite convenient to store one's music collection on the hard drive(s) of a persona! computer, where the entire musical library can be organized and easily played back.

• But clocking problems need to be addressed when transferring the music from the computer to a high-performance sound system.

• Key issue: the master audio clock is in the wrong place-the computer, acting as the dise transport.

• The DIA converter must lock onto the signal coming from the computer and reconstruct a new master dock using a variable-frequency oscillator, which cannot achieve the low jitter levels of a fixed-frequency master clock.

• The original way to play the audio via a computer was with a soundcard that was installed on the PC motherboard. Low-quality switching power supplies and a chassis full of RF interference made it difficult to achieve highperformance analog outputs.

• Digital outputs on a soundcard allowed the conversion to analog in a more friendly external environment, but the only standard is the jitter-prone S/PDIF or AES/EBU connection.


0 Computer Audio & System Building Decisions

• Computer-based audio is basically about 3 key objectives: 0 To digitize favorite tapes/LPs & copy CDs for archiving & back-up 0 To organize audio tracks & downloads in an audio library & playlists 0 To listen to these audio files on a Hi Fi system (PC= jukebox)

• Once the decision has been made, a whole number of hardware & software options must be reviewed & evaluated in terms of budget & performance.

• He re is a brief outline of the number of factors & variables to consider: 0 Computer: desktop or laptop, PC or Mac, OS, CPU, RAM, connectivity,

HDD vs SSD, speed, noise levels 0 Ripping software: EAC, CD Ex, Max ... 0 Format: lossless or not, wav, aiff, flac, a lac, m p3 0 Tagging & metadata, album art covers 0 Storage: HDD, SSD, NAS 0 Playback software: iTunes,J River, Foobar, MediaMonkey, Amarra ... 0 PCI-PCie soundcard or not, ASIO or not 0 Critical choice of a DAC for connection to amps & speakers 0 Which digital audio interface: S/Pdif,AES3, Toslink, USB, FireWire, Ethernet 0 Cabling requirements (digital, analog, power) 0 Clocking thru outboard reference master dock ? 0 Overall system optimization

J F Vignal 1 SAE Brussels-AEDS 908 1 201 0 16

0 0 Audio File Formats

0 Lossless Formats ALC, AiFF, FLAC, FLA,WAV, PCM, WavPack, Monkey Audio, AIF, CDA,Apple Lossless

0 Lossy Formats MPC, MP+, MPP, MPI, MP2, MP3, MP4, LossyWAV,WMA,WMV,AU, OGG, AAC, MOY, AVI, AU, IFF, SVX, SND,AAC,APE, MAC,VOC, mp3PRO

lossless Stereo: Speed Rates vs Frequency (kbps)

Fs (kHz) 16-bit 20-bit 24-bit

44,1 1411,2 1 764,0 2116,8

48 1536,0 1920,0 2 304,0

88,2 2822A 3 528,0 4 233,6

96 3 072,0 3 840,0 4 608,0

176A 5 644,8 7 056,0 8467,2

192 6144,0 14112,0 9 216,0

384 12 288,0 28 224,0 14 832,0

• Wav/ Aiff ( 1 6-bit 1 44, 1 kHz) => 1 41 1 ,2 kbps => 1 min = 10 MB

• Flac: 700-900 kbps • mp3 (CBR): 128-320 kbps


0 0 Which Audio Format For Ripping ?

• Decreasing cost of HDD storage: 1 TB = +/- 90 Eur. • Lossless encoding: Wav/Aiff or Flac, preferred option for archiving &

playback. • Flac currently offers the best compromise quality 1 size. • Size of 1 CD= 700 MB at 1 411,2 kbps. • Flac will compress roughly down to 60% (mp3 in 320 kbps will compress

down to 25%, with loss of details, transients & spatial elues). • Using Flac, 2 400 CDs can be backed up on a 1 TB HDD.

JFYignal/ SAE Brussels-AEDS 908/ 2010 18

0 0 TheASIO ModeAiternative

High Quality Aucf10 Files

WAV 1 FLAC 1 APE

Mixer (Crossfading)

'

Source: http://www.al bum pl ayer.com/features. htm

Volume Control Equalizer

DSP Functions

Driver

Windows WDM Mixer Driver


0 Computer Audio: A Strategie Breakthrough For Hi End Dealers

o • Computer Audio has slowly arrived in the Hi Fi market, like a messiah for the worried Hi End segment of the industry, already challenged by the rise of Home Theater/Multiroom & TV consumer electronics.

• Hi end dealers had been 'conditioned' for decades to glorify the virtues of traditional stereo, with a multitude of brands & products.

• Co ming from vinyl & tubes, with sometimes indecent gross margins, getting on the learning curve for new AV technologies has caused a strategie shakedown of Hi Fi dealers, as weil as a breakthrough.

• The arrivai of Computer Audio, after sorne period of self-deniai both from the press & golden ears, has finally initiated a who le new outlook for the Hi Fi industry (and no doubt, revised business plans as weil).

• The newfound cooperation between computers and Hi Fi opens up a whole market potential, together with a sharp increase in integration competencies -- and a de facto gap with the older, more traditional Hi End customers still debating the virtues of single-ended triodes ©

• As always in a booming market, it's interesting to note how quickly the priee extremes in the retail market set themselves up.

• Today, these retail priee extremes for stereo DACs start from 150 Eur ali the way up to 15 000 Eur. Again, China vs the US.


0 High Resolution Music Downloads

• One of the advantages of computer audio is the ability to download high-res audio files (PCM 24/96 or more, wav, flac, wma, a lac, DSD).

• The benefit is to enjoy master tape quality performance • Several companies are now active in this new business:

0 http://www.21.no/hires/index.html 0 https:/ /www.hdtracks.com/ 0 http://www.rhino.com/shop/format/Digital 0 http://www.bowers-wilkins.com/display.aspx?infid=3550 0 http:/ /www.hiresmusic.com/homepage.htm 1 0 http://www.linnrecords.com/ 0 http://www.referencerecordings.com/HRx l .asp

• Most of the high-res music available today focuses on independent artists but Rhino has started offering Flac on popular rock bands.

• For the highest resolutions, the Norwegian label 2L offers for free a limited number of downloads in DSD.

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JFVignal/ SAE Brussels-AEDS 908 1 2010 22

0 Overview Of Digital Audio Interfaces

0 Specifie interfaces ded icated to digital audio include:

·j • A2DP via Bluetooth • AC'97 (Audio Codee 1997) interface between integrated circuits on PC

motherboards • Intel High Definition Audio A (= replacement for AC'97) • 125 (lnter-IC sound) interface between integrated circuits in consumer

electronics • ADAT interface • AES/EBU interface with XLR connectors • AES47, Professional AES3 digital audio over Asynchrone us Transfer Mode

networks • MADI Multichannel Audio Digital Interface • MIDI low-bandwidth interconnect for carrying instrument data; cannat carry

sound but can carry digital sample data in non-realtime • S/PDIF, either over coaxial cable or optical (TOSLINK) • TDIF (Tascam) proprietary format with D-sub cable • Any digital bus (e.g., USB, FireWire, and PCI) can carry digital audio. • Note: OtherAN interfaces are also engineered to carry digital video and

audio together, including HDMI and DisplayPort. Source: http://en.wikipedia.org/wiki/Digital_audio


0

0 Clocking & Synchronicity

• Synchronous Two synchronous deviees have a single clock source and there is no delay between them.

• Asynchronous Two asynchronous deviees have absolutely no relation to each other. They are free-running with separate docks.

• lsochronous Two isochronous deviees have the same dock but are separated by a fixed propagation delay. They have a phase difference but that difference remains constant.


0 D AC'97

• Short for Audio Codee '97; a Iso MC'97, short for Modem Codee '97) is Intel Corporation's Audio Codee standard developed by the Intel Architecture Labs in 1997, and used mainly in motherboards, modems, and sound cards.

• Audio components integrated into chipsets consists of two components: an AC'97 digital controller (DC97), which is built into the 1/0 Controller Hub (ICH) of the chipset, and an AC'97 audio and modem codees, which is the analog component of the architecture.

• AC'97 defines a high-quality, 16- or 20-bit audio architecture with surround sound support for the PC that is used in the majority of today's desktop platforms.

• AC'97 supports 96,000 samples/second in 20-bit stereo resolution and 48,000 sam pies/second in 20-bit stereo for multichannel recording and playback.

• lntegrated audio is implemented with the AC'97 Codee on the motherboard, a Communications and Networking Riser (CNR) card, or an audio/modem riser (AMR) card.

• ln 2004, AC'97 was superseded by Intel High Definition Audio (HD Audio).

JFYignal / SAE Brussels-AEDS 908/ 20 10 25

0 0 HDAudio

• Intel High Definition Audio (a Iso cal led HD Audio or Azalia) refers to the specification released by Intel in 2004 for delivering high-definition audio that is capable of playing back more channels at higher quality than previous integrated audio codees like AC'97.

• Hardware based on Intel HD Audio specifications is capable of delivering 192-kHz 32-bit quality for two channels, and 96-kHz 32-bit for up to eight channels.

• Like AC'97, HD Audio is a specification that defi nes the architecture, link frame format, and programming interfaces used by the controller on the PCI bus and by the codee on the other side of the link.

• Microsoft Windows XP SP3 and la ter Windows versions include a Universal Audio Architecture (UAA) class driver which supports audio deviees built to the HD Audio specification.

• Mac OS X has full support with its AppleHDA driver.

JFVignal 1 SAE Brussels-AEDS 9081 2010 26

0 D 125

• 12S, also known as lnter-IC Sound, lntegrated lnterchip Sound, or liS, is an electrical seriai bus interface standard used for connecting digital audio deviees together (developed by Philips in 1986).

• lt is most commonly used to carry PCM information between the CD transport and the DAC in a CD player.

• The 12S bus separates dock and data signais, resulting in a very low jitter connection. J itter can cause distortion in a d igital-to-analog converter.

• The bus consists of at least three li nes: 1. Bit dock line 2. Word dock line (also called word select line or left right dock) 3. Data line (at least one multiplexed line)

• The following lines can also be found: 4. Master dock (typical 256 x bitclk) 5. A multiplexed data line for upload

• Very few audio companies offer an 12S physical interface cable between CD transport & DAC (PS Audio, Ste llo, Zanden), with different connectors.


0 AES-EBU (AESJ)

c. AES/EBU was designed primarily to support PCM encoded audio in either DAT format at 48kHz or CD format at 44.1 kHz.

• AES/EBU allows the data to be run at any rate, and recovers the dock rate by encoding the data using biphase mark code (BMC).

• The AES3 standard matches part 4 of the international standard IEC 609S8 for digital audio interfaces (IEC 609S8-3= consumer use, IEC 609S8-4= pro use).

• The following 3 types of connections are in common use: 0 Type 1 Balanced - 3-conductor, 1 1 0-ohm twisted pair cab ling with an XLR

connecter, used in professional installations (AES3 standard). Dual wire is required to output a digital signal at 24/176.4 and 24/192 kHz.

0 Type Il Unbalanced - 2-conductor, 7S-ohm coaxial cable with an RCA connecter, used in consumer audio

0 Type Il Optical - optical fiber, usually plastic but occasionally glass, with an FOS connector, also used in consumer audio (Toslink)

0 The AES-3id standard defines a 7S-ohm BNC electrical variant of AES3 • AES3 digital audio format cana Iso be carried over an Asynchronous Transfer

Mode network. • The standard for packing AES3 frames into ATM ce lis is AES47, and is a Iso

published as IEC 6236S.This requires a CATS or CAT6 type of network infrastructure to SUpport this. JFYignal/ SAE Brussels-AEDS 908/ 2010 28

0

• AES3 is a seriai digital bit stream containing audio that has been digitized using the technique of linear pulse code modulation.

• Each digital audio sample word is represented in linear two's complement binary form.

• Two audio samples are time-division multiplexed to make up a frame, with each audio sample preceded and followed by specialty bits of data.

• The digital data in the frames (except the preamble bits) are represented in a bi-phase mark format.

• With PCM, the amplitude of an analog audio signal is sam pied at a regular rate and at regular intervals of ti me. For audio applications, the most common sampling rate is 44,1 kHz. Here sam pies are taken every 1/44, 1 00 of a second, about every 22.6 J.JS.

'um~rof

bits ( 1)

per digital Wl d

2

1 Total Number T T\\O's Compkmenl Ranet: 1 of ! 2~ 1 IP ( 2' · · 1 ) ' Quantir.tl ion ~ j lc\ cl~ (2'') j

ignal to oi~ Ratio (6.02 x N) · 1.76 9lU dll 122.2 ofl 146.1 dB

- -·

Clock

Data

1 0 0 1 1 0 1 0 0 1 0

Encoded (BMC)


0 D S/PDIF

• There are no differences between the signais transmitted over optical or coaxial S/PDI F connectors-both carry exactly the sa me information.

• Selection of one over the other rests mainly on the availability of appropriate connectors on the chosen equipment and the preference and convenience of the user.

• TOSLINK cables do not work weil (and may even suffer permanent damage) if tightly bent, and the ir high light-signal attenuation limits their effective range to 6.1 meters (20 ft) or so.

• On the other hand, TOSLINK cab les are not susceptible to ground loops and RF interference, like coaxial cables.

• Another deciding factor for many is cast: any standard 75 0 AN cable can be used for coaxial connectivity, while TOSLINK requires a specifie cable which, until recently, was not very affordable.


1 ( / _ _...... .. -"""

--· Main differences between AES 1 EBU and 5/PDIF

......_

0 AES/EBU balanced AES/EBU unbalanced S/PDIF ( ... _ ;

-Cab ling 1 1 0-ohm shielded TP 75-ohm coaxial

75-ohm coaxial or _..-

fibre

Wiki 3-pin XLR, 25-Pin D- RCA, BNC, or Tech Con nectar

subminiature BNC

TOSLINK

Note #1 Output level 2 to 7 V peak to peak

1 to 1.2V peak to 0.5 to 0.6 V peak to peak peak

Min Input level 0.2V 0.32V 0.2V

Max distance IOOm IOOOm IOm

Modulation BiRhase mark code BiRhase mark code BiRhase mark code

Subcode information ASCII ID text ASCII ID text SCMS copy protection info

Max. Resolution 24 bits 24 bits 20 bits (24 bits optional)


0 0 MADI

• Multichannel Audio Digital Interface, or MADI, is an industry-standard electronic communications protocol that defines the data format and electrical characteristics of an interface carrying multiple channels of digital audio.

• The AES standard for MADI is currently documented in AES 1 0-2003. • The MADI standard includes a bit-level description and has features in

common with the two-channel format of AES3. • MADI is widely used in the audio industry, especially in the professional

sector. • lts advantages over other audio digital interface protocols and standards

such as AES/EBU (AES3), ADAT,TDIF and S/PDIF are: first, support of a greater number of channels per line; and second, the use of coaxial and optical fiber media that enable the transmission of audio signais over 100 meters and up to 3000 meters.

• Seriai digital transmission over coaxial cable or fiber-optic lines of 28, 56, or 64 channels is supported, with sampling rates of up to 96 kHz and resolution of up to 24 bits per channel.

JFYignal/ SAE Brussels-AEDS 908/2010 32

0 IEEE 1394

o • The 1 EEE 1 394 interface is a seriai bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used by persona! computers, as weil as in digital audio, digital video, automotive, and aeronautics applications.

• The interface is also known by the brand names of FireWire (Apple), i.LINK (Sony), and Lynx (Texas Instruments). IEEE 1394 replaced parallel SCSI in many applications, because of lower implementation costs and a simplified, more adaptable cabling system.

• IEEE 1394 was adopted as the High-Definition Audio-Video NetworkAIIiance (HANA) standard connection interface for AN (audio/visual) component communication and control.

• FireWire is also available in wireless, fiber optic, and coaxial versions using the isochronous protocols.

• lt remains the primary transfer mechanism for high end professional audio and video equipment.

• Since 2003, many computers intended for home or professional audio/video use have built-in FireWire/i.LINK ports, especially prevalent with Sony and Apple's computers.

• The legacy (alpha) 1 394 port is also available on premium retail motherboards. JFYignal/ SAE Brussels-AEDS 908/ 2010 33

0

0 USB

• USB was originally seen as a complement to FireWire (IEEE 1394) and designed for simplicity and low cast, while FireWire was designed for high performance, particularly intime-sensitive applications such as audio and video.

• USB networks use a Master-Siave topology, wh ile FireWire networks use a PeerTo Peer topology.

• USB 1 .0, 1.1 and 2.0 use a "speak-when-spoken-to" protocol. Peripherals cannat communicate with the host unless the host specifically requests communication. USB 3.0 is planned to allow for device-initiated communications towards the host.

• A USB network relies on a single host at the top of the tree to control the network. ln a FireWire network, any capable node can control the network.

• USB runs with a 5 V power li ne, wh ile Firewire (theoretically) can supply up to 30V.

• The chipset and drivers used to implement USB and Firewire have a crucial impact on how much of the bandwidth prescribed by the specification is achieved in the real world, along with compatibility with peripherals.


Wiki Tech Note #2

0

• Non return to zero, inverted (NR 1s a me g bin to a physical signal for transmission over sorne transmission media.

• The two level NRZI signal has a transition at a dock boundary if the bit being transm itted is a logical one, and do es not have a transition if the bit being transm itted is a logical zero.

• "One" is represented by a transition of the physical level. "Zero" has no transition.

• Also, NRZI might take the opposite convention, as in Universal Seriai Bus (USB) signaling, when in Mode 1 (transition when signaling zero and steady level when signaling one).

• The transition occurs on the leading edge of the dock for the given bit. This distinguishes NRZI from NRZ-Mark.

• However, even NRZI can have long series of zeros (or ones if transitioning on "zero"), so dock recovery can be difficult unless sorne form of run length limited coding is used on top.

• USB uses bit stuffing, which is efficient, but results in a variable data rate: it takes slightly longer to send a long string of 1 bits over USB than it does to send a long string of 0 bits. (USB inserts an additional 0 bit after 6 consecutive 1 bits.)

111°1 1111°1°1°1 1111°1 11°1 Ô=:J 0 1 1 0

10110010 0 35

0 Digital Audio Interfaces: Key Specifications AES/EBU (AES3) Inputs

Type Balanced, differentiai Impedance 110 n Sensltivity (unloaded) 1- 10 v pk-pk Maximum Wordlenglh 24 bits Con nectars XLR3 female (2) Connections Pin 1 Grou nd or shield

Pin2 +Signal Pin3 -Signal

SPDIF (electrical) Input REG Output

Type Single ended, ground referred

Impedance 75 75 n Sensillvity (unloaded) 0.5 1.0 v pk-pk Maximum Wordlenglh 24 24 bits

Conne ct ors RCA Phono RCA Phono &BNC

SPDIF (optical) T oslïnk Input ST Input

Type Optical

Wavelength 660 850 nm Maximum Wordleng1h 24 24 bits

Connector Toslink ST EIAJ CP-340 (if fitted)

SOIF 1 Wordclock Input Output

Type Single ended, ground referred

Impedance 100 25 n Sensrtivity (unloaded} TTL TTL Connectors BNC BNC

IEEE 1394 uo Type High speed, mu/ti-channel

Data format dCS encrypted DSD Connectors 6-way (2}

Source: http://www.dcsltd .co.u ki page/assets/Del i usManual.pd f J F Vignal 1 SAE Brussels-AEDS 908 1 201 0 36

0 Summary: Digital Audio Interfaces & Key Benefits

}EJ AES/EBU (AES3) • Sampling Rate: 32 kHz to 96 kHz (single mode) to 176.4-192 kHz (dual AES3) • J itter rejection, shielding/noise rejection, dual wire upsampling ( 1 76.4-192 kHz)

0 S/PDIF • Sampling Rate: 32 kHz to 96 kHz PCM • J itter rejection

0 Toslink • Sampling Rate: up to 24 bits and 48kHz PCM (96kHz in sorne cases) • Electrical/galvanic isolation

0 USB Audio Class • B-Type connecter: up to 24 bits and 96kHz PCM • Ease of set-up, convenience (USB On The Go), up to 384kHz with custom driver

0 FireWire • Up to 24 bits & 192 kHz PCM & DSD • Speed, peer-to-peer protocol, dual wire (DSD), multichannel


0


D S/Pdif and 125

• S/PDIF (part of the expanded AES3 digital interface specification) is the industry standard for real-time transfer of digital audio from one consumer audio product to another.

• Within a product the same digital audio signal is transferred between deviees via a different interface called 125 (also known as 125 or liS).

• 125 uses three separate connections- audio data, word clock and bit clock- whereas S/PDIF combines ali three signais into one using bi-phase coding.

• As a result, when S/PDIF is decoded inside an external DAC the data, word clock and bit clock have to be separated.

• But when the dock is recovered its frequency can be modulated by the digital data, resulting in data-related jitter.

• Conventionally this effect is reduced using a phase-locked loop (PLL) to recover the clock.

• PLLs work by continuously comparing the incoming clock with the regenerated clock using a long time constant, with the result that shor tterm fluctuations in clock frequency are attenuated.


0 S/Pdif & jitter Generation

• S/PDIF is poorly designed. Either a separate dock line should have been used, or (better) the system should have been designed so that the transport can be slaved to the DAC.

• ldeally the master dock must be positioned close to the DAC chips for best audio performance

• When the dock and DAC chips are dosely positioned & coupled, timing errors are minimized.

• When a CD player is connected to an external DAC via S/PDIF, the master dock is in the CD player and the DAC chips are in the DAC, i.e. they are separated by the S/PDIF interface.

• The DAC has to recover the dock from the S/PDIF signal, and this can easily introduce timing errors (jitter).

• Moreover, S/PDIF circuitry represents a radio frequency (RF) noise source and its presence in a CD player is audible.


0

0 Types Of jitter

Interface JJlter

Interface and Sampll ng Jitter

lnterfenng Noise Jitter

Sources of Interface Jltter

Source: http://www.tnt-audio.com/clinica/diginterfl _e.html

Analog Audio Unit


0 Toslinl< & jitter Generation

0 Advantages Of Optical • Electrical (galvanic} isolation from EMI/RFI inside the computer (switch

mode power supply) • Toslink can provide a dock but one issue is the high amount of jitter. • However jitter is masked as white noise, and in fact can sound quite good

as most converters can handle this weil (the PLLs have an easier job).

0 Disadvantages of Optical • Limited to 24/96 • As the optical version of S/PDIF,Toslink requires a soundcard (except on

Mac's) • Toslink has a lot of jitter, due to the electrical to optical conversion • Frequently suffers from poor hardware implementation, cheap and

substandard parts.


0 Splitting the CD player into Transport & DAC

• A well-designed one-box CD player places a fixed-frequency master audio dock right next to the DIA chip for the best possible audio performance.

• ln contrast, a two-box CD system splits the system into a dise transport box and a D/ A converter box.

• The two are normally connected with the industry-standard S/PDIF or AES3 connection which places the master audio dock in the transport box, where it is mixed together with synchronization codes and the audio data and transm itted to the D/ A converter box.

• The DIA converter box must then attempt to recover the critical master audio dock from this jumble of signais for delivery to the Dl A chip itself.


0

0 lntegrated Cd Player

1 ntegrated CD Pfeyer

Trans~ort Ana log Audio Unit

lntegrated CD Plaver Configuration

Source: http://www.tnt-audio.com/clinica/diginterfl_e.html


0

0 The Two-Box CD Player

• The standard solution for a two-box CD player is to use a PLL (PhaseLocked Loop) to control a VCO (Voltage-Controlled Oscillator) in the Dl A box, generating the master audio dock.

• The VCO varies its frequency in order to lock onto the incoming signal sent from the transport box.

• Unfortunately, a variable-frequency oscillator sim ply cannot achieve the low-jitter performance of a fixed-frequency crystal oscillator.

• Over the years many schemes have been implemented by various manufacturers in attempts to improve the jitter performance of the S/PDIF connection.

• These include dual PLL's,VCXO's (Voltage-Controlled Crystal Oscillators), frequency synthesizers, FIFO (First-ln, First-Out) buffers for the audio data, or external re-clocking deviees ("jitter reduction").

• Wh ile ali of these methods are able to reduce the jitter levels, they cannot eliminate the jitter that is inherently added by the S/PDIF connection.


D Typical S/pdif 1 nterface CD Transport & DAC

CO dise

Motor, servos & laser

S POif

Digttal filter DAC chip

Phase locked loop t~dOdt (PLL} 1---..;.....;..;.....; __ --r--------_,

recovered dock

SIPDIF receiver

Digttal filter DAC chlp

Source: http://www.nai m-audio.comldownload/Naim _ DAC_ White _ Paper _ AuL 2009 .pdf


D ASRC (Asynchronous Sample Rate Converter)

; 0

• Another approach to redu ce j itter that has become increasingly popular in recent years is to use an ASRC (Asynchronous Sample Rate Converter) chip.

• The original audio data is replaced with newly calculated data that represents wh at the audio data would have be en if the incom ing signal had most of the jitter filtered out.

• The technical theory behind this method is sound, as demonstrated by the measured performance, which is generally quite good. However the audible performance of these deviees is controversial, as it completely discards the original audio data.

• The only correct solution is to place the critical master audio dock in the DIA converter box, next to the DIA chip itself.

• This has been done in a few products using separate transports and DIA converters, but there have been drawbacks to these solutions.

• One scheme added a separate cable that carried the master audio dock signal back upstream to the transport box.

• While able to achieve low levels of jitter, this new interface was no longer compliant with the SIPDIF standard.

• lnstead a closed system was created that only worked with specifie pairs of transport and Dl A converter boxes from a single manufacturer.

J F Vignal 1 SAE Brussels-AEDS 908 1 20 1 0 4 7

0 D Signal Rate Conversion (SRC)

Synchronous SRC • The output dock is synchronized to input dock. • This mode is recommended for Digital to Digital transfers.

Asynchronous SRC • The output dock is generated by internai dock generator. • This mode is recommended for Digital to Analog transfers where the

SRC proceeds a DIA converter in order to upsample the signal and provide 100% jitter immunity (eg., Tl/Burr Brown TAS 1 020B chip).

• Usually, upsampling from Red Book specs 16/44,1 to 24/96 or more. • Also used for DSD upsampling ( 1 bit/2,24 Mbps) via DSP (Delta Sigma

modulation & noise-shaping).

JFYignal 1 SAE Brussels-AEDS 9081 2010 48

INTEGRATED CO PLAYER

0

NORMAL CONFIGURATION

S/PDIF

Data+ Clock

--.. Clock flows

Source: http://www.tnt-audio.com/clinica/diginterfl_e.html

0 S/pdifTopologies & Design Variations

•

•

•

•

•

The two sub-units are synchronized by a single master dock, which drives both of them: that is, data are read out of the CD, transferred to the DIA converter and converted into music according to the pace stated by this master dock. Other derived dock info (bit dock, word dock, Ir dock, depending on the specifie chips used) are transferred from the transport sub-unit to the DIA converter, but are in any case synchronous with the master clock

The S/pdif interface uses a special code, named biphase-mark. 1 n this code any bit is transmitted by a sequence of two half bits, but the combination rule is such that there must always be at least one transition (from low to high or vice versa) for each transmitted bit. This allows to transfer not only the data content, but also precise dock information.


NORMAL CONFIGURATION WITH SPDIF RECLOCKING

S/PDIF

--• Clock flows

NORMAL CONFIGURATION WITH DOUBLE PLL

SIPDIF

Data +Ciock

--• Clock flows

• Structural problem in the S/pdif interface, as the biphase-mark code used, causes interference between data and clock information

•

•

•

•

The dock information is in sorne way mixed up, polluted and confused by the data, and any reconstructed clock suffers from data dependent jitter Need to supply the DAC with a dock as clean & stable as possible. The better the clock from the transport, the better the reconstructed dock at the DAC. One solution is to re-dock the S/pdif flow just before it leaves the transport with the deanest available dock.

• The standard PLL (phase locked loop) systems used by the standard receivers to retrieve the dock are recognized as not good enough for high end audio.

• Often a second, much more tight and stable PLL, based on a voltage controlled crystal oscillator (VCXO) is added after the receiver just to utterly stabilize the clock


NORMAL CONFIGURATION + CLOCK •

0 • SIPOIF

Data+ Clock

--+ Clock flows

liS (125) CONNECTION

---+ Clock flows

The simplest approach is to transmit the dock separately. This solution is normally used in professional environ ment, where it is necessary to keep many different cards and units perfectly

synchronized.

• A rather special implementation recently adopted (by NorthStar, for example) is to extend the 12S interface outside the transport through a multi-wire interconnect to the DAC unit.

•

•

This has a further benefit, in that it does not require any S/pdif transmitter and receiver at ali, but only a simple array of li ne driver and receivers, and ali the circuit can be far simpler. No standard has been defined, and each implementation is therefore quite different.


"CLOCK BACKWARDS" CONFIGURATION

0 S/PDIF

Data(+ Clock)

CLOCK

--• Data flows

--+ Clock flows

" CONTROL BACKWARDS" CONFIGURATION

S/POIF

Data(+ Clock)

--+ Clock flows

• Another solution proposed by a few companies (eg.,Wadia) is to move the master dock where the cleanest dock is needed: in the DAC unit itself.

• ln this configuration the transport (slave) is receiving a degraded, possibly jitter affected, copy of the dock.

• The job of the transport is to provide a flow synchronous with the DAC dock, while dock precision can be assured simply by re-docking the signal just before entering the DAC, the transport jitter causes no problem at ali, unless it causes digital transmission errors.

• Linn, after studying the problem, decided that transferring the dock back caused too much RF interference.

• To avoid transferring a high frequency signal, and taking into account that the S/pdif flow transports even dock information that is made available in the DAC by the receiver, they decided to synchronize the transport using what could be defined as a .. distributed phase locked loop (PLL)".


0 A Recent DAC Topology:The Naim DAC (20 1 0)

. ~~-·

~~ wr><• ..,._ --fmrtp:m.

.,._ 1 fk!l.!Œf dOCk$

,,~;:~:-·pt~

' "'" ''* ..... ~

:;, ""'t<'l Slackf•fl St'!t\RC® (;OtJI)lel ® i

OS? OSF' ~ola:wn

,,..., ""=:· use ..... us - ~;.AA·~

Rc~ing , . ., sw1ch ilt<l

""" . -}1 l i

. ! ~ . . . . . . AcPlll

l OC<ll . Twof>CM1704

~ OSP rt, .... .

Autne..,bcat .on : OACchlps cloc< . . . .. .,.,.,... . _, .

ii . . .

:-_.. '"' ~ n r S:POIF ;.~~, : . 12\1 ~ . . . . . . . oi

• ! . . l~ . . . . . . . : :: Poww supp . .e!l lor AAM lrd e«oor .. : • • : : OSP lllOO o! ~lion bulfor . ar..1JOO•lelder . . . .. . ; ~

. . 'tt,

. ~ if :, . .,, . . .

fermer :: ·····································•f••········,.······················,····,.··· f~fin;ary

~~ ,

.. p '<!I$UW" ~for 300 or®r .. •Hll• .. analr..g aicl& of i&olator ar~atogue fi' er . . :: ......

Source: http://www.naim-audio.com/download/Naim_DAC_ White_Paper _Aug_2009.pdf


0


0

0 Oversampling & Reclocking: 6 Digital Setups

• This section illustrates the comparison of six digital setups. • Each of these setups uses the same converter chip, the PCM 1704. • ln these simple schematics, you can see what possibilities engineers have to

overcome Jitter before audio conversion at the converter chi p. • Every incoming S/PDIF signal is Jittered.That's why this is important.

• Setup # 1: Digital Slave Mode - No Oversampling - No Reel oc king • Setup #2: Digital Slave Mode- 8x Oversampling- No Reclocking • Setup #3: Digital Slave Mode - 8x Oversampling - Asynchronous Reclocking • Setup #4: Digital Master Mode, 8x Oversampling, Single-stage Synchronous

Reclocking • Setup #5: Digital Slave Mode, Upsampling and Asynchronous Reclocking

Together • Setup #6: Digital Master Mode, Upsampling and Synchronous Reclocking

Together

Source: http://www.lessloss.com/page.html ?id =44


0 Setup #1: Digital Slave Mode, No Oversampling, No Reclocl<ing

• The most simple digital configuration possible. • Ali Jitter which is present at the S/PDIF input is contributing to distortion

of the audio signal at the analogue output. • This is the typical scenario when a standard external DAC is used in

conjunction with a CD player. • This scenario is called Digital Slave Mode because the DAC receives its

dock signal from the external CD player's oscillator .

......


0

D Setup #2: Digital Slave Mode, 8x Oversampling, No Reclocking

• Oversampling: the frequency of the original clock signal is multiplied by a who le number (i.e. 2, 4, 8, etc.). The idea is that when the converter chip runs at this higher frequency, the low-pass filter after the converter chip can be a simple second-order filter, as opposed to a sixth or higher order filter needed in the case of no oversampling.

• This leads to less distortion, which effect is easily audible and is not to be doubted in any way.

• Based on the Shannon-Kotelnikov sampling theorem, the low-pass filtering should ideally eut off the first frequency which is above the Nyquist frequency.

• Because analogue filtering causes the least amount of distortion when the slope is soft (i.e. first or second order which means 6 or 12 dB per octave, respectively), oversampling helps achieve the conditions where such a filter can be used to achieve the desired attenuation of the first frequency which is above the Nyquist Frequency.


o 0 Setup #2: Digital Slave Mode, Bx Oversampling, No Reclocking

• Ali Sigma/Delta type converters contain Oversampling (wholenumber multiple) built in as an integral part of the chi p.

• The PCM 1704, in contrast, is a parai lei resistor type converter which requires any Oversampling to be done externally by another chip dedicated to this process.

• This is more expensive, is more laborious to build, and sounds better.

,....

S/PU1 ~

OVERSAMPUNG OF'1

(loc- oscillator is in t"• c• player. Aelj~o~st th• c:lo<l('s JHt,er • ount -.,l.th tn• fad•~"·


0 D Setup #3: Digital Slave Mode, Bx Oversampling, Asynchronous Reclocking

• This method is used to attempt to reduce the Jitter present in Method #2 above.ln this example,Jitter is indeed reduced, because the new oscillator is located right next to the digital signal it is newly clocking.

• This avoids new introduction of line-induced Jitter. However, we are now dealing with two Master Clocks simultaneously.

• Part of the problem here is that no two clocks ever tick at the exact same pace.

• Another part of the problem is that the further clock signal is always more J ittered than the nearer clock signal.

• Therefore, we encounter an inevitable frequency d iscrepancy between the se two clock signais, and this leads to distortion of t~e audio signal due to the real-time digital interpolation algorithm employed.

JFYignal/ SAE Brussels-AEDS 908 / 2010 59

o 0 Setup #3: Digital Slave Mode, 8x Oversampling, Asynchronous Reclocking

• Even though Asynchronous Reclocking do es not bring about an actual sampling rate conversion, (which would then be called Asynchronous Resampling), the method of Asynchronous Reclocking cannat actively rem ove ali present Jitter artifacts from the original data stream.

• lndeed, by usingAsynchronous Reclocking (two separate docks), sorne amount of existing Jitter is actually fed into the newly clocked data stream.

S/PUf -+ ,--

!RECEIVER 1 CS84!6

CLOCJ: -+ .:cc_ t J,

r-·-. r · !ou:ux:""'"f nnnn !OVERSAMPLING

"' UUUU 1 DFI706

ASYNCHRONOUSOSCkLATOR

Clock oscillator is in the CD player. Adjust the clock' jlttor a~ount with tho f•oor.

ANALOGUE


o 0 Setup #4: ) Digital Master Mode, Bx Oversampling, Single-stage Synchronous

Reclocking

• Here the re is only one dock source, and this is located right next to the converter.

• The source deviee accepts the same dock as the converter. • Not only at the same frequency, but the same dock signal itself. • Everything is kept in perfect synchronization, and line-induced J itter which

appears on the long path between the oscillator, through to the source deviee, then back to the S/PDIF input, is quantized to perfection via the synchronously running oversampling chip.

• This is called Master Mode because the dock source is within the DAC, and the deviee contains only this one dock source.


D Setup #4: Digital Master Mode, 8x Oversampling, Single-stage Synchronous

0

) Reclocking

• This is the method we recommend using, because it is the method which annihilates Jitter the most effectively.

• The addition of multiple stages of this type of completely Synchronous Reel oc king lessens J itter even more.

• By appropriately applying the completely Synchronous Clocking and multiple-staged Reclocking solution, no digital compromises are made and a Jittered signal coming off of the laser mechanism of a CD player is improved upon in real time as it reaches the DAC chip.

RECEJVER

+-'11l11fL

1. aYNCHRONOU& ~PliNG

OFt~

Clt:ldl Of..ltp'Jt t.o...._""""""" ________ ..,......,., 1~0Pl~

lhoro is "O clo<k oscill•tor 1n tho CD p ~y•r · The o"lY clock o~cill•tor is hereo in the ~AC ·


o 0 Setup #5: .! Digital Slave Mode, Upsampling and Asynchronous ReclockingTogether

• Asynchronous Reclocking With Upsampling is the method used when you want to achieve a frequency other than a whole-number multiple of the S/PDIF input frequency.

• i.e. from 44.1 kHz input we want a 48kHz output • Multiple of 1.0884353741496598639455782312925 • Or from 44.1 we want 96 kHz • Multiple of 2.176870748299319727891156462585 • This is also known as Sampling Rate Conversion. • lt is important to note that in Asynchronous ReclockingWith Upsampling, a

separate dock is used with a different operating frequency than that of the original dock.


0

D Setup #5: Digital Slave Mode, Upsampling and Asynchronous Reclocking Together • Setup #5, shown below, is the best possible solution for those who wish not

to modify an existing Master CD player (original CD-internai dock remains, running the player).

• The market is full of such solutions. • Although the Jitter reduction using this method is very exceptional, the user

will still encounter the traditional audible differences between digital cables, cable lengths, and jittery playback deviees.

• Using Setup #5, even with the highest quality digital cabling, it is impossible to achieve the sound quality which is achieved using Setup #4 above (Multiplestaged Synchronous Reclocking).

RECEJVER Csa415 1

UPSAMPUNG A01896A . U U U l.J PCM17il4 ~ ~ f/

n n n n , .. ·--·- --~~~-- -- ~ ____,. A~) ~ 1

.__, __ _. ANALOGUE

~t ASYN<:HROHOOS OSCILLA TOR

f1rst clock oscîllator 1s în the CD player. ~djust the clock's jitter aMount with the faoor.

'------------- ------JF Vignal/ SAE Brussels-AEDS 908 1 20 1 0 64

.,_ -~,.,. 1

1-------------0 Setup #6: Digital Master Mode, Upsampling and Synchronous ReclockingTogether

· ·0

• The standard frequencies which allow simple Oversampling (x2, x4, x8) of 44.1 kHz audio are the following: 11.2896 MHz, 16.9344 MHz, and 33.8688 MHz.

• This is so because the numbers 1 1289600, 16934400, and 33868800 ali divide evenly by 441 00, which is the typical sampling frequency used in the consumer S/PDIF standard.

• Because the standard oscillator in DVD players runs at either 27 MHz or 54 MHz (for video purposes), a Phase Locked Loop (PLL) is used within universal DVD/CD players to achieve the 44.1 kHz needed for consumer CD audio.

• If we want to slave a universal DVD/CD/SACD player to a DAC, the DAC must contain the 27 or 54 MHz generator. Because we are on a 27 or 54 MHz dock, we must therefore use Asynchronous Upsampling, because 27 or 54 MHz cannot be divided evenly by 44.1 kHz.

• This renders the question of highest possible quality audio from DVD players moot.

• ln this case, at best, we have a high-quality dock upgrade to a DVD player, coupled with a quite effective Jitter suppressing solution.

• The creators of the DVD playback deviees sacrificed high quality audio for a frequency compatibility with their video schematic solution (it was probably cheaper that way).


0

0 Setup #6: Digital Master Mode, Upsampling & Synchronous ReclockingTogether • And this is the very reason why, using our method (Setup #4), a higher quality

sound is achieved by playing CDs at 44.1 kHz than is possible if we were to offer this mathematically inferior DVD solution at even 96 kHz.

• Many audiophiles and the more honest dealers tend to agree that weil engineered CD playback solutions sound just as good as DVD or SACD.

• Our solution goes to the extreme and it puts the CD format in the forefront of the new format dise playback solutions.

• Until higher resolution formats can be played back in both a mathematically synchronous way and through parai lei-resistor type converters (PCM audio instead of bitstream), the CD remains the best digital source out there.

• lnterestingly, the mass-market, in its scramble for attention, has prematurely moved on and has never utilized the CD format to its full potential. Haste makes waste.

......

StPtlf _.

n n n n RECBVER ~ UU U U CWHS

UPSAioiPLING DAC PCI.t!T~

----'ANALOGUE

ClQd( ~ ~~------OSC-IU.A-TOR ___ _....)

PJ...,.... tZ7 or 91 ft.!Z l

first •synchronous ••ths in sl•v•d •vp pl•y•r· Adjvst jitter aaQunt due to this process with the raoer .


D Specs Chart Of DAC Chips by Manufacturer (ca. 2007) Feature Crystal Wolfson Burr-Brown Burr- Burr- Burr- Analog Analog

0 Brown Brown Brown Deviees Deviees

DAC chip r ' ' ' t ~ '4 >

Resolution 24 bit 24 bit 24 bit 24bit 24 bit 24bit 24 bit 24 bit

Max Sampling frequency 192 195 200 200 200 200 192 192

[KHz]

THD@ OdB & 44.1 KHz -1 OOdB -104db 0.0005 0.0005 0.0004 0.0004 -123dB -IIOdB [%]

THD@ OdB & 96KHz[%] -IOOdB -104db 0.001 0.001 0.0008 0.0008 -133dB -IIOdB

Dynamic range 44.1 KHz 117 117 123 126 129 132 120 123 [dB]

Dynamic range 96KHz [dB] 117 117 123 126 129 132 120 123

DAC S/N 100 120 123 126 129 132 120 db 120

Outputs peak to peak 1.4Vpp 2Vrms 4.0mA 8.0mA 7.8mA 15.6mA 8.64mA 17.28mA

Source: http://www.audiodesignguide.com/DAC _fi nai/DacFinal.html


0

0 Specs Chart Of DAC Chips by Manufacturer (ca. 20 1 0)

Fe at ure Analog Deviees AKM Burr Brown (Tl) Burr Brown (Tl) ESS Wolfson

DAC Chip AD1955 AK4397 DSD1792A PCM1704 Sabre32 WM 8741

Resolution 24/192 + DSD 24/192 + DSD 24/192 + DSD 24/96 32/500 24/192 + SACD

Technology Multibit Multibit Mult ibit R2R Multibit Multib it

Delta Sigma Delta Sigma Delta Sigma Delta Sigma Delta Sigma

DAC S/N (dB) 120 123 127 120 134 123

THD+N (dB) 120 105 0,0004 0,0008 118 100

Source: Revue Du Son, No 345, November 2009


0 USB Deviee Class Definition for Audio Deviees (release 1.0, March 1998)

• The USB is very weil suited for transport of audio (voice and sound). • ln addition, the USB has more than enough bandwidth for sound,

even high-quality audio. • Many applications related to voice telephony, audio playback, and recording can

take advantage of the USB. • An essential issue in audio is synchronization of the data stream s. • The smallest artifacts are easily detected by the human ear. • Therefore, a robust synchronization scheme on isochronous transfers has been

developed and incorporated in the USB Specification. • The Audio Deviee Class definition adheres to this synchronization scheme

to transport audio data reliably over the bus. • Audio synchronization types are briefly described in the next slide.

Source: http://www.usb.org/developers/devclass_ docs/audio 1 O.pdf


0 Audio Synchronization Types Each isochronous audio end point used in an Audio Stream ing interface belongs to a synchronization type as defined in Section 5 of the USB Specification. 0 Asynchronous • Asynchronous isochronous audio endpoints produce or consume data

at a rate that is locked either to a dock external to the USB or to a free-running internai dock.

• These end points cannot be synchronized to a start of frame (SOF) orto any other dock in the USB domain.

0 Synchronous • The dock system of synchronous isochronous audio endpoints can

be controlled externally through SOF synchronization. • Such an end point must do one of the following:

,/ Slave its sample dock to the 1 ms SOF tick. ,/ Control the rate of USB SOF generation so that its data rate becomes

automatically locked to SOF. 0 Adaptive • Adaptive isochronous audio endpoints are able to source or sink data at any

rate within their operating range. • These endpoints must run an internai process that allows them to match their

natural data rate to the data rate that is imposed at their interface. JFVignal/ SAE Brussels-AEDS 908/2010 71

0 D The USB Protocol

• USB as its name indicates is a seriai connection (the S in USB). • Ali connected gear shares the same internai path and data is

dropped/picked-up in packets hopefully at the right place and time. • ln addition USB connections are managed by the computer's processor

which may have more urgent things to do than send data to the DAC -like loo king up the latest Windows updates online or running anti virus software.

• This can generate potential timing errors or altogether dropped data. • The only exception being the isochronous USB DACs by Wavelength

Audio, Ayre and dCS which manage their own USB connection and secure a minimum of calculation power from the processor to ensure proper operation.

• Refer to next section on USB Adaptive vs Async for more details.


0 jitter & USB Audio

• With USB came a mode that is supported under ali operating systems called Asynchronous USB.

• Unlike ether USB DACS (Adaptive) the DAC actually controls the flow of data and operates ali the internaii2S protocol and DAC clock using a very low jitter Master Clock.

• No longer is it required to fix the jitter as there was very little from the start. • Adaptive mode USB on the other hand is required to change the clock every

1 ms which in itself adds jitter to the system. • The Master Clock in Adaptive systems that gene rates ali the 125 signais is

derived from a programmable high jitter clock. • Ali of these types of products usually use sorne sort of method to Fix Jitter (eg.,

secondary PLL, FIFO's, reclockers, upsamplers) otherwise it would be too high to tolerate.

Source: http://www.usbdacs.com/Concept/Concept.html


0 0 USB DACs & Clocking

• The critical factor about adaptive vs asynchronous USB modes is clocking. • Clocking is extremely important with digital audio to achieve the most

accurate sound Qitter-free). • Two clocking strategies are possible:

0 Keeping the dock as close to the DAC chip as possible, sending dock from the DAC to the front end components.

0 Using an external master dock (eg., Ante lope, Apogee, dCS) to connect ali digital components to the same dock source.


D Any advantages of converting from USB to S/pdif?

• The main use of turning an USB audio stream to S/PDIF is to avoid using the PC's or Mac's internai digital output interface, which is affected by a relevant jitter and is generally limited to 24/96, operation (when not to 16/48).

• Also, using the internai USB input of most DACs should be avoided because it generally suffers the same limitations of the PC's and Mac's outputs.

• Moreover, most DAC's USB inputs work in isochronous mode and not in asynchronous, generating jitter.


0 USB 2.0

• USB (Universal Seriai Bus) was developed by a consortium of corn panies in the 1990s. lt was incorporated as a standard in the same year that IEEE-1394 was standardized.

• USB features a master-s/ave configuration • that requires a host (master) and a client

(slave). • USB is controlled through the host and is

typically referred to as the host control/er. • Most often, the host is a persona! computer.

This configuration requires overhead on the host side in order to maintain the transfer of data between host and client, hence reducing overall sustained data rates.

• If communication between two clients is needed, then the data rates are reduced even further.

/~ (-:( t , _:\ ~8G H: Host C: Client

USB: Master-Siave Network topology

Source: http://www.qimaging.com/support/pdfs/firewire_ usb_ technote.pdf


0 Advantages of USB

• USB allows to eliminate the S/PDIF interface. S/PDIF interleaves the sample rate with the digital data. By eliminating the S/PDIF entirely, its associated jitter can be eliminated.

• USB interfaces are a much "deaner" approach toward data transfer. • J itter destroys many spatial eues • USB has the advantage of widespread support, as weil as drivers that come

with the operating system. • USB is the only interface that can have Async protocol. Not supported by

Firewire, AES/EBU, S/PDI F or Toslink. • Async protocol allows the master dock to be located at the designation

deviee, either a converter, redocker or the DAC itself, which is the optimum scenario.

• This establishes the master dock near the DIA conversion and controls the source rate using a flow-control protocol.

• New spec added in 2001, USB "On The Go": PC no longer required as host (for example, a USB key can be plugged directly into a P$3).


0 Disadvantages of USB • Current sample rate limitation at 16-24/48 (native). • 24/96 can be achieved with the Burr Brown TAS 1 020B chip (USB 1.1) and

third-party driver made by Centrance. • Cannot run at high sample rates using the standard drivers. Possible to

work at 96/24, but not input and output simultaneously. • As an audio transport, USB actually needs to use sorne of the CPU

resources to operate. • The USB port that the DAC is connected to is always competing for time

on the bus with ali other USB connections in the system. • The additional resources and resource sharing needs of USB can make the

audio stream turn on and off as it's routed to the DAC. • The buffer in the DAC can compensate for it, but it still causes a number of

problems with jitter and timing. • Unidirectional, does not work for multichannel.

0 Future Developments of USB • USB Class 2.0 with 24/192 capability and ab ove natively without drivers. • This is available now on MAC OSX 1 O.S.x but not in Windows or Linux

y et. • USB 3.0 SuperSpeed.


D FireWire /IEEE-1394

• Developed by Apple Computer in the 1990s, FireWire was eventually proposed as a replacement for SCSI (Small Computer System Interface) by the IEEE (lnstitute for Electrical and Electronics Engineers).

• 1 EEE-1 394 employs a peer-to-peer connection.

• Peer-to-peer networks use the power of connected participants as opposed to relying on a small, concentrated number of servers.

• The advantage of this strategy is that 1 EEE-1 394 provides sustained data rates without requiring a computer host for interconnection between peripherals.

P: Peer

PeerTo Peer Protocol

Source: http://www.qimaging.com/supportlpdfs/firewire_ usb_ technote .pdf


0 D The FireWire Protocol

• FireWire was the solution developed to answer those potential issues for video editing and music playback.

• FireWire gear can operate in an almost completely autonomous fashion thanks to an onboard processor which controls the relationship with the computer to relieve the main processor and enable smoother data transfer even during processor overloads.

• Besides throughput, other benefits are that it uses simpler bus networking, provides more power over the chain, more reliable data transfer, and uses fewer CPU resources.

• For audio, the IEEE 1394 is a high-speed multichannel digital interface. lt can carry over 50 channels of DSD or over 30 channels of 24 bits 1 192kHZ audio data thru a single cable.

• Because of its high sensitivity to j itter, word dock synchronization (ideally to an outboard master dock) is recommended.

JFVignal/ SAE Brussels-AEDS 908 / 20 10 80

0 D FireWire & jitter

• FireWire can be operated in 2 modes: D The asynchronous operating mode, similar to USB. D The isochronous mode that allows deviees a dedicated amount of

bandwidth. This insu res the audio stream will keep flowing without interference from collisions or glitches.

• USB DACs work great as long as there are no other deviees on the USB bus that interfere with the DAC, i.e. keyboard, rn ouse, trackpad, printer.

• USB also puts more load on the CPU. Fortunately for many computers this load is negligible when audio is streaming to an external DAC.

• FireWire does seem like the way to guarantee a smooth audio stream to the DAC, but it is not without its detractors.

• Sorne in the industry prefer USB 1.1 because it allows a 24/96 audio stream without the need to install additional deviee drivers.

• Traditionally FireWire also has more jitter than USB interfaces. AJitter Elimination Technologies QET) PLL is used to minimize jitter to extremely low intrinsic levels.


Advantages of FireWire

• Support a sample rate of 24/192 (USB is currently up to 24/96 only). • Fi re Wire is a peer-to-peer protocol: any deviee in a Fi re Wire network can

share data with each other without a host computer. • FireWire supports a streaming mode, called isochronous mode transfer. • FireWire does not need CPU cycles to transfer data, and has a dedicated

transfer bus. • FireWire has wider bandwidth and can transfer audio data in isochronous

mode, with guaranteed bandwidth (CPU resources needed are set aside). • Suitable for stereo & multichannel • ln addition, Firewire (and USB) do not inherently carry a clock and do not

influence jitter (if they do then jitter can be affected). • With Fi re Wire, the computer can be slaved to the master clock in the DAC. • Properly implemented it has less jitter (Dice Il chip), less buffer under- and

overuns, and less stress on the DAC, which preserves the musical signal with better integrity.

• Other benefits: hot pluggable, daisy-chaining, multiple speeds on one cable.


D Disadvantages of FireWire

• Typically legacy drivers for FireWire connected deviees are unavailable for operating systems.

• Thus a DAC manufacturer would have to write and offer a custom-made driver for every operating system.

• FireWire emits large amounts of RF radiation requiring care in shielding the analog converter.

• Poor at transmitting a stable clock, so outboard clocking is recommended. • Except for Mac, not ali desktops/laptops include FireWire: Need for

PCI/PCie controller card or ExpressCard for laptops.

0 Future Development

• Apple has dropped F/W on the basic Mac Book but offers FW800 on Mac Pro, Mac Book Pro, Mini and iMac.

• Available deviees in 2010 with IEEE 1394b forS 1600-53200 speed rates ? • Competition against USB 3.0 and E-SATA (and HDMI v 1.4 ?) .


0 USB & FireWire Speed vs Other Digital Interfaces

Deviee Speed (bit/s) Speed ( Byte/s}

Bus AGP8X 17,066 Mbit/s 2,133 MB/s

PCI 32-bit 66Mhz 2,133 Mbit/s 266.7 MB/s

PCI-e 2.0 x16 64,000 Mbit/s 8,000 MB/s

Peripheral FireWire 400 393.216 Mbit/s 49.152 MB/s

FireWire 800 786.432 Mb i t/ s 98.304 MB/s

FireWire 1600 1,573 Mbit/s 196.6 MB/s

FireWire 3200 3,145. 7 Mbit/s 393.216 MB/s

USB 2.0 Hi-Speed 480 Mbit/s 60 MB/s

USB 3.0 5 Gbit/s 625 MB/s

Audio 5/PDIF 3.072 Mbit/s 0.384 MB/s

AES/EBU 2.048 Mbit/s 0.256 MB/s

MADI 100 Mbit/s 12.5 MB/s

HO HDMI v1.3 10.2 Gbit/s 1.275 GB/s


0 0 Summary: FireWire Comparison with USB

• High-speed USB 2.0 (480Mbps). • FireWire 400 (400Mbps). • Data transfers over 5400 FireWire interfaces generally outperform

similar transfers over USB 2.0 interfaces. • This is likely due to USB's reliance on the host-processor to manage low

level USB protocol. • FireWire delegates the same tasks to the interface hardware (requiring

less or no CPU usage). • For example, the FireWire host interface supports memory-mapped

deviees. • This allows high-level protocols to run without loading the host CPU

with interrupts and buffer-copy operations. • FireWire 800 is substantially faster than Hi-Speed USB.


~1__2]. 1-- - - ~ ~ 4 3 2 1 .:l 3

Type A Type 8

Mini-A Mini-B

ç S.l3Zl J 1 C~ ..... -) 1

n S J l2 1 ? c C:-~- )

t,lrcro-AB Micro-8

FireWire

4-Pin ilink

FireWire 400 6-Pin A.lpha Connector

USB Speed Rates • USB 1 .0= 1.5 Mbps • USB 1.1 = 12 Mbps • USB 2.0= 480 Mbps (Hi Speed) • USB 3.0= 5 200 Mbps (Super Speed)

FireWire Speed Rates • S 1 00= 1 00 Mbps

FireWire 800 9-Pin Beta Connector

• 5200= 200 Mbps • 5400= 400 Mbps • 5800= 800 Mbps • S 1600= 1600 Mbps • 53200=3200 Mbps


0

Source: http://www.cablewholesale.com/i nd ex. php ?section= Support&bo dy= U sb3


0


0

0 The Market Boom For USB DACs

• Currently the most common way to bring the audio data out of the computer to a high-performance audio system is via the USB port.

• ln recent years, there has been an explosion of external USB DIA converters.

• Retail priees cover the who le range from 200 Eur to 13 000 Eur. • The advantage of this approach is that any music player software may be

used-iTunes,J. River, Windows Media Player, Foobar, WinAmp, Media Monkey-so the customer is able to select the application that fits his needs the best.

• What has enabled this proliferation of USB-based DIA converters is a series of chips from Burr-Brown (Texas Instruments) cal led the PCM270x senes.

• These chips are inexpensive (only a few dollars), very easy to use, and require no programming skills.

• They are similar enough to conventional DIA chips that any digital audio engineer can easily design a product around them.

Source: http://www.ayre.com/PDF/Ayre_ USB_ DAC_ White_ Paper.pdf


• But ... the Burr-Brown PCM270x chips have high levels of jitter. • A fixed-frequency master audio dock is not employed.lnstead a variable-

o frequency master audio dock is generated based on the timing of the incoming audio data.

• The computer sends packets of audio data at one millisecond intervals across the USB connection.

• This system, ca lied "adaptive" USB mode, creates several opportunities where jitter will be added to the DIA converter's master dock:

0 Any variable frequency dock will intrinsically have more jitter than an equivalent fixed-frequency clock.

0 ln the "adaptive" USB mode, the dock in the DIA converter must "adapt" to match the rate that the computer sends out audio packets.

0 The computer cannot send audio packets at a perfectly fixed rate. The computer's internai clock is not designed to have low jitter (cost factor). Secondly, the inside of a computer is fil led with RF interference, impacting the dock stability.

0 The Burr-Brown USB-enabled DIA chips update (change) the frequency of the master audio clock each ti me a packet of audio data is received.This happens once a millisecond so there will be a strong jitter component at 1 kHz, right in the middle of the audio band.

0 Finally, the PCM270x chips are limited to 16/48.

JFVignal 1 SAE Brussels-AEDS 9081 2010 90

0

0 Background Of Asynchronous USB

• At the same time thatTexas Instruments was developing the PCM270x USB-enabled DIA converter chips, they also developed an obscure part cal led the TAS 1 020B Stereo USB Audio Interface chi p.

• This chip integrates multiple functions into one part-a USB transceiver, a microprocessor, a memory controller with a FIFO buffer, and an 12S interface to allow easy connection to A/D and DIA converter chips.

• Obviously this chip is very powerful and offers great potential to the digital audio designer.

• The difficulty is that this chip is a blank slate-completely unusable unless programmed.

• A third-party company, CEntrance, has been certified by Texas Instruments to develop software for the TAS 1 020B.

• Their code allows high-resolution audio data (up to 96/24) to be transmitted across the USB port but doesn't address the jitter issue.

• A new code was developed by Wavelength Audio, using asynchronous USB data transmission.


0 0 USB DACs: Adaptive Mode

• Currently almost ali USB DACs use Adaptive Mode USB Audio. • Even the latest native 24/96 USB DACs using CEntrance code (like the

Benchmark DAC 1 HDR) use ·Adaptive USB Mode. • ln Adaptive mode the computer controls the audio transfer rate, and the

USB deviee has to follow along updating the Master Clock (MCLK) every one millisecond.

• The USB bus runs at 12MHz, which is unrelated to the audio sample rate of any digital audio format (i.e. 44.1 K requires a MCLK = 11.2896MHz).

• Therefore Adaptive Mode USB DACs must derive the critical master audio dock by use of a complex Frequency Synthesizer.

• Since the computer is handling many tasks at once, the timing of the USB audio transfers has variations.

• This leads to jitter in the derived dock. (Adaptive USB description courtesy ofWavelength Audio)


0 USB DACs: Adaptive Mode

TAS1020B AUDIO USB CONTROLL.ER

AOAPTIVE USB AUDIO

FREQUE:NCV MCLJ( O>

SYNTHESlZER )oc no DAC oo

t t 0 ln

f2MHZ % , ... ;o

USB PLL ::0 ;; r--- 0 ose ,.. r

COMPVTER' S USB

1 DATA 'T

Source: http://www.usbdacs.com/Concept/Concept.html


0 D USB DACs: Asynchronous Mode

• Asynchronous Mode USB enables the USB DAC to control the computer.

• Asynchronous Mode works by using an ultra law jitter master dock in the DAC that contrais the audio transfer rate from the computer. According to Wavelength Audio, "Jitter is reduced by a factor of greater than 100 times."

• This is accomplished using the standard USB drivers (Windows or Mac OSX) for easy plug-and-play installation.

• Current DACs using similar Asynchronous implementations are the Ayre QB-9 (code licensed from Wavelength Audio) and the USB products from dCS.

.···.~ . "'~ ....- . /:. ·. "~ '

. ~ ..::.~~ l


0 USB DACs: Asynchronous Mode

Low JJTTER TAS1020B OSCILLA TOR

AUDIO usa CONTROl.I..ËR ~

ASYNCHRONOUS USB AUDIO

0 )> MCLK

)> c 0 0 DAC 0 0 0 U) z I'Q

t2MHZ -{ » USB r-- PLL :u ; 0

ose r- r COMPVT R'S USS

1. OAYA ~

Source: httpJ/www.usbdacs.com/Concept/Concept.html


0 0 Summary

• Asynchronous USB essentially turns the computer into a slave deviee as opposed to adaptive USB which does the opposite.

• Th us, an asynchronous USB DAC has total control over the timing of the audio.

• One very important feature of asynchronous USB mode is bidirectional communication between the computer and the DAC.

• The computer sends audio and the DAC sends commands or instructions for the computer to follow.

• For example the computer's dock becomes less accurate over a given period of ti me and can send too much data too quickly and fi li up the buffer.

• Asynchronous DACs will instruct the computer to slow down, thus avoiding any negative effects of a full, or empty, buffer which can manifest itself into audible dropouts and pops or clicks.

• Plus ali of this is done without additional deviee drivers or software installation.


0


0 Ethernet 1 LAN Digital Interface • The protocol of this network interface include the flow-control and retry

o mechanisms that enable the optimum audio streaming scenario, as weil as having the advantage of avoiding altogether the audio software stack of the computer OS.

• Using networked deviees, either wired or wireless, can be no different than sending data to a printer.

• The only con cern is getting the data to the deviee intact. The re is no timing information sent or implied.

• The data is not contiguously streamed at real-time speed as with USB, FireWire or S/PDI F interfaces.

• lt is packetized and sent periodically in high-speed bursts over the network, whenever the network has an "opening".

• These packets are then collected in a buffer memory at the destination deviee where they can be clocked out to the D/A using a locallow-jitter master dock.

• The fact that networked data flow incorporates flow-control and retry, and bypasses the computer audio stack makes it the superior method.

• As for bandwidth, networked interfaces can not only support the highest audio sam pie-rates, such as 24/192, but multiple channels as weil, allowing for multiple channel playback and even movie surround-sound.


0

0 Ethe rn et DAC Advantages

• An Ethernet DIA converter allows to avoid the S/PDIF connection jitter 1ssues.

• An Ethernet DIA converter can have a fixed-frequency master audio dock inside of it, sending commands to the computer to request more audio data to fill the D/A converter's buffer.

• Technically, this is an excellent approach and is able to provide true low-jitter performance.

• A similar approach can be taken with FireWire, although most computers do not provide the hardware support for this connection.

• The computer cannot send audio packets at a perfectly fixed rate. • Firstly, the computer's internai dock is not designed to have low jitter. • ln a market segment where costs are literally shaved to the fractions of a cent,

it would add too much the cost of a computer to use a high-performance, low-j itter dock.

• Secondly, the inside of a computer is fil led with RF interference, making it impossible for even the best of docks to maintain their spectral purity.

• ln the following si ides, we'll review the step-by-step implementation of an Ethernet DAC, based on Linn's Klimax DS.


0 0 Ethernet DAC Disadvantages

• The player that interfaces to the network is currently a custom player, such as Linn, Sooloos, Squeezecenter or Sonos.

• These custom-made solutions are not inexpensive. • They require firmware/driver updates • Hopefully, in the future Microsoft and/or Apple will create more generic

player software to drive a networked interface so that more player options will be available.


0

D Typical Flow Chart of Ethernet DAC Implementation

• e e

Pronto Control

Klimax Room

Klimax DS

i-Touch / PDA

Control

Kitchen

Sekrit. DS-1

i e e

OS Multi-Room

r- --------------- - -- - --~ 1 Daia Storage & Network Infrastructure ; 1 1

Router

NAS WAP

SWitch

Source: http://www.linn.eo.uk/multi-room ds

PC Control

Sekrit DS-1

Bedroom

-

. ! ~, - )

Ke

Etheroet

Analogue Audio

D1gital Audio

--HDMI--

- RS232--

~ WoFi


0 0 Step 1 : Connect PC to Router

1 LAPTOP 1-1 ---11 ROUTER 1 • Connect the two deviees directly using a standard Ethernet cable • (RJ-45, Cat S)(crossover is not necessary). • Configure the PC's network adaptor (NIC) to obtain IP address

automatically by DHCP. • Disable any wireless NI Cs which are present on the PC. • Configure the router to have an IP address of 192.168.72.1, and enable

it's DHCP server to issue IP addresses in the range 192.168.72.1 00 ... 200.

Source: http://docs.linn.co.uklwiki/index.php/DS Network Setup


o D Step 2: Connect PC, Router & NAS via Switch

LA PT OP NAS ROUTER

1 1 1 1

SWITCH

• Connect the Laptop, Router, and NAS to the Ethernet switch. • Configure the NAS to obtain it's IP address automatically via DHCP

and disable its DHCP server.

JFVignal/ SAE Brussels-AEDS 908/ 20 1 0 103

o D Step 3: Add DACTo Network

LAPTOP NAS ROUTER

1 1 1 1

os ,___ SWITCH Note: DS= DAC

• Connect the DS product to the Ethernet switch as shown in the diagram. Switch on or power cycle the DS.

• When powered up, the DS dis play, or LED on its front panel, should flash for a few seconds then remain on continuously.

• If it continues to flash, this indicates that it has failed to obtain an IP address (via DHCP). If this happens, check ali network connections and the router configuration.


o D Step 4: Add DS To Network

LAPTOP NAS ROUTER

1 1 1 1

os HOME Vt J\., HOME SWITCH i-- 1-PLUG N v PLUG Note: DS= DAC

(If Homeplugs are not being used this step may be skipped).

• lnsert the HomePiugs into electrical mains sockets as shawn in the diagram.

• Disconnect the DS from the switch and reconnect it to one of the HomePiugs.

• Connect the other HomePiug to the switch. • Power cycle the DS and verify that it gets assigned an IP address via

DHCP from the router. • If the DS does not get an IP address check ali network connections and

troubleshoot the HomePiugs if necessary.


0

0 Step 5: Add Wireless Access Point (WAP)

LAPTOP ))~ (V"RELESS) 1)

Note: DS= DAC

WAP os

L, SWITCH

HOME ~

PLUG

NAS ROUTER

1 1

~ HOME SWITCH

~ PLUG ~

(If wireless control is not being used this step may be skipped) • Configure the WAP to obtain IP address automatically via DHCP. • Connect the DS, HomePiug and WAP together using a switch as indicated in

the d iagram. • Power cycle the DS and verify that it gets assigned an 1 P address via DHCP

from the router. • If the DS does not get an IP address check the network connections

between the DS and the switch and between the switch and the HomePiug. Power cycle the WAP.

• Disconnect the Ethernet cable from the laptop. Enable wireless connectivity on the laptop and ens ure it connects to the correct WAP.

• Run LinnGui and test that the DS is controllable wirelessly by playing a track from the NAS on the DS.


o D Step 6: Add Wireless Control Point

PDA (WlRELESS)

c Note: DS= DA

WAP os

~ SWITCH --

LAPTOP

1

HOME ~ HOME PLUG N--I/ PLUG

NAS ROUTER

1 1 1

1-- SWITCH

If wireless control is not being used this step may be skipped.

• Disable wireless connectivity on the laptop and reconnect it to the switch using the Ethernet cable.

• Switch on the PDA and open the KinskyPDA application. • Test that it is possible to play a track from the NAS on the DS

using the PDA.


0

D Step 7: Add Additional Audio Deviees

PDA DSî DS2 PROXY LAPTOP NAS ROUTER (WI ELESSJ

....,_

'-.../ 1 ~ 1 1 0 1 1

WAP SWITCH HOME [A J'-._ HOME

SWITCH Note: f- t--PLUG f"r v PLUG DS= DAC

If additional Linn audio products are not being used this step may be skipped.

• Connect other, network enabled, Linn deviees to the switch as shown in the d iagram.

• Open LinnConfig and check the room name of each deviee. • Give ali deviees the same room name by using the "Advanced Configure"

ta b. • If using an RS232 control led preamp see Adding a proxy preamp.

J F Vignal 1 SAE Brussels-AEDS 908 1 20 1 0 1 08

0

0 Step 8: Add Internet Router

POA DS1 DS2 .- ... PROXY LA PT OP NAS ROUTER (WIRELESS)

'--' 1 ~ 1 1 0 1 1

WAP SWITCH HOME /l J'. HOME

SWITCH INTERNET 1---

PLUG .'1 1/ PLUG ,_..

ROUTER

• Connect the "Internet" (WAN) port of the router to an internet router which is already connected to the internet. Reboot the WAN router.

• Open a browser on the laptop and check that it is possible to access internet. • Open CD ripping application (example EAC) and test that the application can

retrieve CD metadata from the internet. • If there are any other computers or deviees which need access to the DS

subnet, these should be connected to one of the switches or the WAN router, and not connected d irectly to the internet router.

• If there are computers or deviees which need access to the internet, but denied access to the DS network, these should be connected directly to the i nte rn et router.

• For a more detailed description of this see Configuring The Router: Network Positioning

JF Vignal/ SAE Brussels-AEDS 908/ 2010 109

0

0 The Digital Home ConceptToday

HomePiug Applications

Sroadband TV ~PTV)

Broadband Sbarlng

Powerline Ethernet Internet \

Internet

Source: http://wificentral.co.uklpub/files/images/wired/1259250438_ homeplug-av-apps.gif

Wlteklss Extender

l : ml!lp$ i Ho!NI'lllt Ut11blgEtttllllor ;

JFVignal/ SAE Brussels-AEDS 908/2010 Il 0

0

JFVignal/ SAE Brussels-AEDS 908/ 2010 Ill

0 I DSD .._______ i CHrect Stream Digital L __

• Trademark name used by Sony and Philips for the introduction of the Super Audio CD (SACD) in 2000.

• The signal is stored as Delta-Sigma modulated digital audio, a sequence of single bit values at a frequency sampling rate of 64 times the CD Audio sampling rates of 44.1 kHz, for a rate of 2.8224 MHz ( 1 bit times 64 times 44.1 kHz).

• On the DVD dise, 3 audio layers can be available: SACD Stereo, SACD 5.1, and standard CD Stereo.

• Noise shaping occurs by use of the 64x oversampled signal to reduce noise/distortion caused by the inaccuracy of quantization of the audio signal to a single bit.

• Therefore it is a topic of discussion whether it is possible to eliminate distortion in 1-bit Sigma-Delta conversion.

Source: http://en.wikipedia.org/wiki/Direct_Stream_ Digital

JFYignal/ SAE Brussels-AEDS 908/ 2010 1 12

PCM

0

Source: http://en.wikipedia.org/wiki/Direct_Stream_Digital


0 D Delta-Sigma DACs

• lnherently excellent linearity. • High resolution possible (24-Bit). • Oversampling relaxes analog antialiasing filter requirements. • Ideal for CMOS processes, no trimming. • No SHA required (sample & hold amplifier). • Added functionality: On-chip PGAs, ana log filters, autocalibration. • On-Chip programmable digital filters (AD7725: Lowpass, Highpass,

Bandpass, Bandstop). • Upper sampling rate currently limits applications to measurement,

voiceband and audio, except for bandpass Sigma-DeltaADCs. • Analog multiplexer switching speed limited by internai filter settling time.


0 DSD-SACD Specifications

0 • SACD audio is stored in a format called Direct Stream Digital (DSD), which differs from the conventional PCM used by the compact dise or conventional computer audio systems.

• DSD is 1-bit, has a sampling rate of 2.8224 MHz, and makes use of noise shaping quantization techniques in order to push 1-bit quantization noise up to inaudible ultrasonic frequencies.

• This gives the format a grea ter dynam ic range and wider frequency response than the CD.

• The SACD format is capable of delivering a dynamic range of 120 dB from 20 Hz to 20 kHz and an extended frequency response up to 1 00 kHz, although most currently available players list an upper limit of 80-90 kHz.

• The process of creating a DSD signal is conceptually similar to taking a 1-bit delta-sigma analog-to-digital (A/D) converter and removing the decimator, which converts the 1-bit bitstream into multibit PCM.

• lnstead, the 1-bit signal is recorded directly and in theory only requires a lowpass filter to reconstruct the original analog waveform.

• ln reality it is a little more complex, and the analogy is incomplete in that 1-bit sigma-delta converters are these days rather unusual, one reason being that a 1-bit signal cannot be dithered properly: most modern sigma-delta converters are multibit.


0 • Because of the nature of sigma-delta converters, one cannot make a direct comparison between DSD and PCM.

• An approximation is possible, though, and would place DSD in sorne aspects comparable to a PCM format that has a bit depth of 20 bits and a sampling frequency of 96 kHz.

• PCM sampled at 24 bits provides a (theoretical) additional 24 dB of dynamic range.

Because it has been extremely difficult to carry out DSP operations (for example performing EQ, balance, panning and other changes in the digital domain) in a 1-bit environment, and because of the prevalence of studio equipment such as Pro Tools, which is solely PCM-based, the vast majority of SACDs- especially rock and contemporary music which relies on multitrack techniques- are in fact mixed in PCM (or mixed analog and recorded on PCM recorders) and then converted to DSD for SACD mastering. Note: Need to include DSD vs PCM in future Digitai/Mastering class at SAE.

Source: http://www.d igi tai audio.dkltechnical_papers/axi on/dxd %20 Resol ution%20v 3 .5. pdf


0 0 DSD Wide 8-bit

• To address sorne of these issues, a new studio format has been developed, usually referred to as "DSD-wide", which retains standard DSD's high sample rate but uses an 8-bit, rather than single-bit digital ward length, but still relies heavily on the noise shaping principle.

• lt becomes almost the same as PCM (it's sometimes disparagingly referred to as "PCM-narrow") but has the added benefit of making DSP operations in the studio a great deal more practical.

• The main difference is that "DSD-wide" still retains 2.8224 MHz (64Fs) sampling frequency wh ile the highest frequency in which PCM is being edited is 352.8 kHz (8Fs).

• The "DSD-wide" signal is down-converted to regular DSD for SACD mastering.

• As a result of this technique and other developments there are nowa few digital audio workstations (DAWs) that operate, or can operate, in the DSD domain, notably Pyram ix and sorne SADiE systems.


• High-resolution PCM (Biu-ray Dise) and DSD (SACD) may still technically o differ at high frequencies.

• A reconstruction filter is typically used in PCM decoding systems, much the same way that bandwidth-limiting filters are normally used in PCM encoding systems.

• Any error or unwanted artifact introduced by such filters will typically affect the end-result.

• If the filter designer chooses a wide, flat passband, then the length of the impulse response will inevitably increase {Time-domain analysis of filters).

• A claimed advantage of DSD is that product designers commonly choose to have no filtering, or modest filtering.

• lnstead DSD leads to constant high levels of noise at these frequencies. • DSD's dynamic range decreases quickly at frequencies over 20kHz due to

the use of strong noise shaping techniques which push the noise out of the audio band resulting in a rising noise floor just above 20 kHz.

• PCM's dynamic range, on the other hand, is the same at ali frequencies. (Sorne high-end SACD players employ an optional low-pass filter set at 30 kHz for compatibility and safety reasons, suitable for situations where amplifiers or loudspeakers cannot deliver an undistorted output if noise above 30 kHz is present in the signal.)


0 DXD

• Another format for DSD editing is DXD (Digital eXtreme Definition), a "PCM-Iike" signal with 24-bit resolution sampled at 352.8 kHz.

• Digital eXtreme Definition (DXD) is an audio encoding scheme for professional use that was developed for editing high-resolution recordings because DSD, the audio standard used on Super Audio CD is not ideally suited for editing.

• DXD is a PCM-Iike signal with 24-bit resolution (256 times the depth of a Red Book CD at 16-bit, since it is exponential) sam pied at 352.8 kHzeight times 44.1 kHz, the sampling frequency of Red Book CD.

• The data rate is 8.4672 Mbit/s per channel- three times that of DSD64. • DXD was initially developed for Merging's Pyramix DSD workstation.


• So what is DXD? SACD is based on a digital processing called DSD, Direct o Stream Digital (DSD64).

• From the Red Book specification (44.1 kHz), the data stream will go through a 1-bit/64 times over-sampling process to achieve an audio date rate of 2.8224 Mbitls.

• DSD signais further require a noise shaping process to sustain the dynamic range of 120 dB within the primary bandwidth of 20 Hz - 20 kHz but that causes the noise spectrum to increase above 22 kHz.

• One obvious solution is the process known as DSD 128, which increases resolution to wider bandwidth by doubling the over-sampling rate to lbit1128 times.

• The down side is that the data size would also be doubled and would require large media storage, rendering it impractical for commercial applications.

• Digital eXtreme Definition is a professional audio format that brings "analogue" qualities in 32 bit floating point at 352.8 kHz.

• DXD preserves 1 1 .2896 Mbitls (4 times the data of DSD). • This leaves headroom for editing and balancing before quantizing to DSD. • The dise stilllooks like a CD and is totally compatible with conventional

CD players and computers.


0

0 High-Res Downloads From Music Label 2L Source: http://www.21.no/hires/index.html

For the same music track (duration 09:24), the hi-res formats & corresponding file sizes can be compared: • Stereo Flac, 24/96= 171 MB • Stereo Flac, 24/ 192= 338 MB • Stereo WAV, 24/96= 304 MB • Stereo DSD 64, 2.8224 Mbits/s= 268 MB • Stereo WAV DXD, 24/352.8= 1 .0 GB

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)

0 Selection Of Stereo DACs & Solutions for Computer Audio

0 1. 2. 3. 4. 5. 6. 7. 8.

USB Adaptive USB Asynchronous FireWire Wi red Ethernet USB to S/pdif adapters AES/EBU Soundcards lntegrated Music Servers Outboard Master Clocks

• With the market boom on Computer Audio, the current offer for USB DACs has quickly multiplied, with products now covering ali priee points.

• USB DACs can be found from 200 Eur to 1 3 000 Eur. • The purpose of this section is to highlight the most notable products

currently available for Computer Audio & music servers, including FireWire, Ethe rn et, USB adapters & AES-EBU PCI soundcards for reference.

• The specs listed for each mode! focus only on digital inputs resolution & sampling frequency. More details (SNR, THD, ... ) can be found on each manufacturer's website.As always, specs & retail priees are subject to change.

• And new DACs are being launched in the market every quarter!


1. USB adaptive DACs > Aqvox USB2 DAC mk2

0

0 4 Digital Audio Inputs • lxAES/EBU, lx S/Pdif, lxToslink, lx USB 0 1 Digital output • S/Pdif, Toslink,AES/EBU-Input are routed to the USB-output (up to 48kHz/16bit) 0 Sampling Rates • AES/EBU & S/Pdif inputs: 16kHz to 192kHz at 16bit 1 24bit • Toslink input: 16 kHz to 96 kHz at 16bit/24bit (up to 176.4--192kHz) • USB- INput and OUTput: 16kHz to 48kHz, at 16bit

(with optional USB 2.0 Upgrade up to 192kHz/24bit, inclusive ASIO) • http://www.aqvox.de/ • Retail 1 1 00 Eur


0

1. USB adaptive DACs> Bryston BDA-1

0 8 Digital Audio Inputs: • lx USB vl.l

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• 4x S/Pdif (co-axial wire) • 2x optical (TOSLINK) • lxAES/EBU • Sample rates: 32kHz -192kHz • 16-24Bit PCM, 16Bit 32K-48K USB • http://www.bryston.com/ • Retail 2 300 Eur

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1. USB adaptive DACs > Benchmark DAC 1-HDR

0 5 DigitaiAudio Inputs • 3x S/Pdif= 28 to 195 kHz • 1 x Optical= 28 to 195 kHz • lxUSB=44.1to96kHz • AdvancedUSB TM computer audio interface for native 24-bit 1 96-kHz

USB audio (no driver needed) • http://www.benchmarkmedia.com/ • Retail 1 900 Eur


1. USB adaptive DACs > Lavry DA-I 1 0

0 4 Digital Audio Inputs • Sample rates between 30kHz and 200kHz, 24-bit (USB 96 KHz) • lx XLR • 1 x USB v2.0 (24/96) • 1 x S/Pdif (Coaxial) • 1 x Optical (Toslink) • http ://lavryengi nee ri ng.com/ • Retail 1 500 Eur

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1. USB adaptive DACs > Grace Design-M902

0

0 4 Digital Audio Inputs • lxAES3 • lx S/PDIF • lx TOSLINK • 1 x USB (USB input supports 16 bit/44.1 and 48k only) • 24bit/ 192kHz digital stereo inputs except USB • http://www.gracedesign.com/ • Retai 1 1 700 Eur

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1. USB Adaptive DACs > Antelope Zodiac+

0 7 Digital Audio Inputs: • lxAES/EBU • 2x S/PDIF • 2x Optical TOSLINK • 1 x USB on mini B type connector

(Custom USB chip streams audio up to 192kHz) • lxWord Clock Input on BNC • 3x Digital Outputs on AES/EBU and S/PDIF • http://www.antelopeaud io.com/en/index.htm 1 • Retail 1 900 Eur


0

1. USB adaptive DACs > Naim DAC

0 8 Digital Audio Inputs: • 2x coaxial BNC • 2x coaxial phono, • 4x optical toslink • 2x USB • Audio files supported: USB =WAV (LPCM up to 768kHz /32bit) 0 Sample Rates • USB 32kHz to 768kHz, 24bit • S/PDI F 32kHz to 192kHz, 24 bit • iPod, iPhone 48kHz max • http://www.naim-aud io.com/ • Retai 1 2 600 Eur


1. USB adaptive DACs >Audio Research DAC 7

0 5 Digital Audio Inputs: • USB: Spec 1 .0 to 2.0, 16 Bit, 32kHz to 48kHz, MAC or PC. • RCA: 75 ohm S/Pdif, 16/32 to 24/192. • BNC: 75 ohm S/Pdif, 16/32 to 24/192. • XLR: 1 1 0 ohm AES/EBU, 16/32 to 24/192. • OPT: 660 NM Toslink fi ber, 16/32 to 24/192. • http://www.audioresearch.com/ • Retail 3 600 Eur


1. USB adaptive DACs > MSB Technology-Piatinum DAC IV

0 5 DigitaiAudio Inputs • 3x S/PDI F (Optical, Coax, Balanced) • lx S/PDIF (BNC) orWord Sync • 1 x MSB Network with dock link • 1 x Optionallnput slot (USB, limited to 96kHz) 0 Upsampling • 44.1, 88.2 and 176.4 to 352.8 kHz at a resolution of 32 bits • 48, 96 and 192 to 384 kHz at a resolution of 32 bits • http://www.msbtech.com • Retail 14 000 Eur


0 2. USB Asynchronous DACs > Ayre Acoustics QB-9

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0 Digital Audio Input: • 1 x USB, 44.1 kHz to 96 kHz (up to 24 bits) • http://www.ayre.com/ • Retail 2 400 Eur

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2. USB Asynchronous DACs > Wavelength Cosecant 0

0 Digital Audio Input: • 1 x USB data input for use with Mac or PCs • Supported input data formats: 16- or 24-bit word lengths • Sample rates: 44.1, 48, 88.2, or 96kHz • Ana log output jacks: 1 pair RCA • http://www.usbdacs.com/ • Retail 2 800 Eur

J F Vignal/ SAE Brussels-AEDS 908 1 201 0 1 34

0

2. USB Asynchronous DACs > dCS Paganini

0 4 Digital Inputs • 1 x USB2.0 interface on a B-type connector. Ope rates in asynchronous mode. • 1 x AES3 on a 3-pin female XLR connector. • 2x S/Pd if on 2x RCA Phono connectors. • Ali digital inputs will accept PCM data at up to 24 bit PCM at 32 to 96kS/s. 0 6 Digital Outputs • IEEE 1394 interface on 2x 6-way connectors.ln DSD mode, the interface

outputs dCS-encrypted DSD ( 1 bit data at 2.822MS/s). • 2x AES3 on 3-pin fe male XLR connectors. Each outputs 24 bit PCM at 32 to

96kS/s, or as a Dual AES pair at 88.2, 96, 176.4 or 192kS/s. • 2x S/Pdif on RCA Phono connectors. Each outputs 24 bit PCM at 32 to 96kS/s. • http://www.dcsltd.co.ukl • Retail 14 000 Eur


0 3. FireWire DACs >Apogee Mini-DAC

0 G E E E L E C T R 0 N 1 C S Mene•a.c:'

0 5 Digital Audio Inputs • 2 x AES-EBU on 9 pin D-Type (breakout cable to 2 fe male XLR-3 required)

Handling sample rates: 44.1 k-192k single-mode and 88.2 k-192k dual-mode. • 1 x S/PDIF optical on TOS-LINK 44.1/48k • 1 x S/PDI F coaxial on RCA 44/l-192k • 1 x FireWire 400 (OSX and Windows XP only) • ADAT 44/1-48k • ADAT/SMUX Il for 88/2/96k • ADAT/SMUX IV for 176.4/192k • http://www.apogeed igital.com/ • Retail 900 Eur


0 3. FireWire DACs >Weiss DAC-2

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0 4 Digital Audio Inputs • 2x Firewire 400 connectors (daisy-chaining) • lxAES/EBU • lx S/PDIF • 1 x Toslink (optical) • Sampling frequencies= 44.1 to 192 kHz, 24-bit • An internai jumper allows to set the XLRIRCA inputs to the dual wire

AES/EBU scheme in the case of 176.4 or 192kHz sampling rates. • http://www.weiss.ch/ • Retail 2 500 Eur


o 3. FireWire DACs > Mytek-Stereo 1 92 DSD

0 6 Digital Audio Inputs • lxAES/EBU • 1 x S/Pdif • lxToslink Optical • lx USB • 1 x FireWire • lx DSD • Resolution & Sampling Frequencies: 24-bit, 32 -192 kHz • http://www.mytekd igital.com/ • Retail 1 500 Eur


0 4. Ethernet DACs > Linn Klimax DS

0 Digital stream player: Ethernet • Supported file types FLAC,WAV, MP3,AIFF • Audio sample rates 7.35 KHz to 192 KHz • Word depth 16 - 24 bits • http://www.linn.eo.uk/ • Retail 1 5 000 Eur


0 S. USB to S/Pdif Adapters > M2Tech-HiFace

• Digital Input: 1 x USB A type male • Output: 1 x RCA or 1 x BNC • 1/0 Standard • 1 np ut USB 2.0 Format • Output S/PDIF Stereo Digital Audio Format • Sampling Frequency= 44.1 kHz to 192kHz • Resolution= 16 up to 24-bit • Custom Driver (Microsoft, OSX and ASIO native drivers= 96kHz max) • http://www.m2tech.biz/ • Retail ISO Eur (RCA) 180 Eur (BNC)


o S. USB To RCA Out > HRT-Music Stream er Il+

0 Digital Audio Input • 1 x USB type 1.1 or above • Data Rate up to 96 kS/s • Bit Depth up to 24 bit • http://www.highresolutiontechnologies.com/ • Retail 250 Eur


o S. USB to S/Pdif Adapters > Bel Canto-USB Link 24/96

• Converts USB computer-sourced files to S/Pdif output • Compatible with native drivers on Mac and Windows • Accepts high-res audio files with data rates up to 24 bits and 96KHz • http://www.belcantodesign.com • Retail 400 Eur


0 S. USB to S/Pdif Adapters > SonicWeld-Diverter 24/96

• Passes up to 24/96 data via USB input • Digital output BNC 750 + RCA adapter plug • No special drivers or software needed • http://www.cryo-parts.com/index.htm 1 • Retail 1 1 00 Eur


0

6.AES/EBU PCI-Soundcards > LynxAES-16

• Sixteen-channel AES/EBU Digital 1/0 • 192 kHz 1 24-bit Single-wire and Dual-wire Modes • Synchrolock J itter Attenuation • Word Clock and Multi-card Synchronization • Powerful Mixing and Routing Engine • Low-latency Drivers for Windows and Macintosh • Cab ling for Direct Digital Interface Yamaha, Apogee, Mackie,

and other Equipment • http://lynxstud io.com/index.asp • Retail 600 Eur

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0 6.AES/EBU PCI-Soundcards > RME Hammerfall HDSP 9632

• Balanced stereo analog in- and output, 24-Bit/192kHz, > Il 0 dB SNR • Optional analog expansion boards with 4 balanced in- or outputs • Ali analog 1/0s capable of 192 kHz, constant number of available channels • 1 x ADAT digital 1/0, supporting 96 kHz S/MUX operation • 1 x S/Pdif digital 1/0, 192 kHz-capable • 1 Breakout cable for coaxial S/Pdif • 1 Stereo head phone output 1 MIDI 1/0 with 16 channels of hi-speed MIDI

via breakout cable • http://www.rme-audio.de/ • Retail 350 Eur


0 7. lntegrated Music Servers > Sooloos

• Hard-drive-based networked music system. • Source-One: system control 1er with 24-bitll92kHz converters, two-channel

ana log and digital outputs, 4-port Ethe rn et switch. • Store-Twinstore hard-drive, mirrored storage for contents of +2000 CDs. • Control-One: 17'' LCD touchscreen display/interface and CD drive. • http://www.m er id ian-aud io.com/sooloos/the-experience.php • Retail from 1 1 000 Eur


0 7. lntegrated Music Servers > Mclntosh MS-750

• Music server with 750GB hard drive, integrated Web interface, CD player/burner, and Ethernet Web interface for rem ote control and music streaming.

• Supported audio formats: Encode: FLAC, MP3. Decode: PCM, FLAC, MP3, WMA,ACC.

• Digital outputs • lx Optical • 2x Coaxial • Sampling frequency: 44.1 kHz • http://www.mcintoshlabs.com/products/default.asp • Retail 8 000 Eur


7. lntegrated Music Servers > Naim-HDX 0

• Sample Rates: 44.1 kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz and 192kHz native • Other rates converted to 44.1 kHz • Bit Depths: 16-bit, 24-bit, 32-bit fixed, 32-bit float • USB: x 1 on the Front panel, x4 on the rear panel • 1 x Ethernet Rear panel RJ45 • Other: PS2 keyboard, PS2 mouse • http:/ /www.naim-aud io.com/index.htm • Retail 6 200 Eur


8. Outboard Master Clocks > Antelope Trinity

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• Rubidium dock input for ultimate performance • 3 lndependent & simultaneous audio generators up to 384kHz • USB connection via PC & Mac allowing full remote control, loading/saving

presets and firmware upgrades • http://www.antelopeaud io.com/ en/products .... trinity.htm 1 • Retail 2 800 Eur


0

8. Outboard Master Clocks > dCS Scarlatti Master Clock

• • - -

• Accepts word dock or AC coup led signais at 32kHz, 44.1 kHz, 48kHz, 88.2kHz, 96kHz, 1 MHz, SM Hz or 1 OMHz. Lock range is +/-300ppm.

• 8 independently buffered outputs on 750 BNC connectors • Clock frequencies: 44.1 kHz or 48kHz, calibrated within +/-1 ppm, (typically

+/-0.1 ppm), temperature compensated. • http://www.dcsltd .co.uklpage/aud ioph ile • Retail 7 800 Eur

J F Vignal 1 SAE Brussel s-AE DS 908 1 20 1 0 1 50

8. Outboard Master Clocks > Esoteric G-Orb 0

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• 1 • 1

• Rubidium Master Clock Generator • Output frequencies: 44.1 kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz,

1OOkHz (universal frequency) • Term inals: BNC coaxial • http://esoteric.teac.com/master mrclocks/g-Orb/ • Retail 14 OOOEur


0


0 0 Conclusion

• Computer-audio playback: a booming market for persona! music libraries. • The end-user has to choose from many options to set up his system, with a

number of variables to evaluate in terms of hardware & software. • One key issue for audio quality playback is the selection of a DAC & audio

interface, although ali system parameters will matter, induding grade of cable. • FireWire, Ethernet or USB each have the ir own merits & demerits, if the

choice of a PCI-PCie soundcard for AES/EBU or S/Pdif output is not an option. • The connection type in itself is less an issue than its proper implementation &

overall performance is much more system-dependent than conventional audio. • Another factor to consider is the budget available for assembling a system. • Lower budgets will favor USB DACs for cost as weil as plug & play. • Bigger budgets will explore FireWire & more likely Ethernet-based servers. • ln any case, jitter management & dock stability are critical factors. • Outboard master docks from Pro Audio offer an alternative solution. • Another strong market trend is the high-res music downloads (24-96 or

more), which is likely to impact the way music is produced in the studio. • Master tape quality is now available for home use. Happy listening!


0 Key Success Factors 0

___ ·. __ -. ) • Obviously with Computer-Audio, many configurations & setups are possible. • And ali the details are important. Below is a checklist for ONE alternative. 0 Computer generation with latest CPU and RAM specs available. 0 External audio interface with FireWire input to AES3 output. 0 AES3 output to stereo DAC digital inputs, then to XLR analog outputs. 0 External CDRIDVDR reader/burner with FireWire connection. 0 Ditto for external hard-disk drives (back-up & playback). 0 Optional outboard master dock reference. 0 Drivers & firmware update. 0 Ripping software: CD-DA Extractor, Max. 0 Ripping format: Flac. 0 Playback software:

./ PC:J River Media Center .

./ Mac: iTunes + Fluke (+Amarra$$$). 0 Windows on Mac (both options above, via VM Ware or similar). 0 Avoid automatic sample rate & depth conversion within the OS or media player. 0 Short audio cables, quality aftermarket cables (discard OE cables). 0 Clean power supply and dedicated power cable for desktop/laptop.


0

0 Computer Audio Dream 1: Let's Go ! FireWire ~· AES3 XLR

~

Weiss Vesta-FW Weiss DAC-202

ATC SCM-20ASL

Toslink 1 USB W/C BNC

Mac Pro iTunes + Amarra

S/Pdif

•

HighFace

USB

iPod

·-dCS Paganini DAC-Upsampler-Ciock

.! XLR

Mel ntosh C-1 000 P

XLR

BeyerT-One

Harbeth Monitor 40.1

t ElectroCompaniet Nemo t iPad 1 NAS 1 Network-Piayer 1

CD/SACD/Biu-ray 1

SAT-Receiver 1 DAB-Tuner 1 USB-Stick JFVignal/ SAE Brussels-AEDS 908/2010

=-------------~ 156

• • •

• •

0 Computer Audio Dream 2: A Full dCS Scarlatti System

The system is synchronized by a Clock running at 44.1 kHz The Upsampler takes data from the Transport or the Laptop (with upsampling set to 24/176.4 or DSD) The DAC takes DSD data from the Transport via 1394, or PCM from the Transport 1 Laptop thru the Upsampler via 1394 (DSD) or Dual AES (24/176.4) Select the DAC input first before using the Sync button to select WCLK Total budget (if you need to know)= 62 000 Eur


0

----........ =---t -----,_,...._ _____ .....,..=------=~JFVignal/ SAE Brussels-AEDS 908/ 2010 158

0

0 Sources & Resources, 1

0 Computer-based Audio http://www.positive-feedbackcom/lssue41/ca intro.htm http://www.anandtech.com/show/2677 http://www.positive-feedbackcomllssue22/nugent.htm http://www.avguide.com/article/music-lover-s-guide-computer-based-music-tas-197 http://stereophile.com/computeraudio/l 008servers/ http://www.thewelltemperedcomputer.com/ http://www.computeraudiophile.com http://www.weiss-highend.ch/computerplayback!white paper computer playbackpdf http://www.6moons.com/audioreviews/pcaudio/pcaudio.html

0 Digital Audio Interfaces http://en.wikipedia.org/wiki/Digital audio http://tweakheadz.com/audio interfaces l.htm http://www.tonmeister.ca/main/textbooklnode591.html

0 S/PdifTopologies http://www.naim-audio.com/download/Naim DAC White Paper Aug 2009.pdf http://www.tnt-audio.com/cl in ica/ diginterf 1 e. html

0 S/Pdif Oversampling & Reclocking http://www.dcsltd. co.u ki page/ myths http://www.lessloss.com/page.html?id=40 http://cplay.sourceforge.net/pmwiki.php?n=CMP.02Upsampling


0 Sources & Resources, 2

0 USB vs FireWire http://www.avguide.com/article/tas-194-the-state-usb-audio http://www.nanophon.com/audio/1394 sampling jitter.pdf http://thewelltemperedcomputer.com/HW/USB DAC.htm http://www.extremetech.com/article2/0,2845,33848,00.asp

0 USBAdaptive vsAsync http://www.avguide.com/article/tas-194-the-state-usb-audio http://www.computeraudiophile.com/content/Asynchronicity-USB-Audio-Primer http://www.computeraudiophile.com/content/Ayre-Acoustics-QB-9-Asynchronous-USB-DAC-Review http://www.ayre.com/PDF/Ayre USB DAC White Paper.pdf

0 Ethernet http://www.avguide.com/buyers-guide/the-absolute-soundhi-fi-guide-disc-players-dacs-music-servers http://docs.linn.co.uk/wiki/index.php/Products

0 PCM, DSD, Flac http://www.digitalaudio.dk/technical papers/axion/dxd%20Resolution%20v3.5.pdf http://www.ps3sacd.com/dsddiscguide.html http:l/blog.bowers-wilkins.com/lab/sound-quality-lab/the-definitive-guide-to-24-bit-flad

FYigr"~al/ SAE Brussels-AEDS 908 1 20 1 0 160

sae_mem_14.pdf

Documents

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