Outboard DAC solutions

Scouring DIY audio forums proved beneficial as I found plenty of attractively priced DAC kits based upon some of the most revered DAC chips available. The availability of USB to I2S and S/PDIF converter boards opens the doors to team commercial outboard DAC solutions as well as complete DIY kit builds to provide a high-end sound experience. DIY solutions are still confined to 16-bit 44.1KHz-48KHz resolution via USB due to hardware/software limitations in the DIY small scale market. It is expected that 2009 will see the availability of 24-bit USB to I2S and S/PDIF chips while Vista should provide native output support for these formats. For now, 16-bit resolution and two-channel playback is adequate for most audio seeing as practically all of our music is recorded with CDs in mind.

Two kits stood out from the pack and present complete solutions that are available in either a modular approach or a single PCB with all components in place to convert data from the digital realm to an audiophile grade audio output. The first is the Doede Douma USB to I2S converter. Doede's solution uses the Texas Instruments 2707 USB to I2S and audio out chip. The venerable TDA1543 is the centrepiece of this kit, favoring a purist mindset as it does not use any kind of oversampling of the digital signal. Audio output from the TDA1543 is configured to use a minimalist passive I/V approach with a final output of 0.6V, which may be a little low for power amplifiers that require higher input voltage to reach full output power. PCM2707 audio output is also available if required, although most people put its subjective abilities behind the TDA1543. Pricing options start at the €49 for the basic kit, while dropping an additional €29 will allow you to experiment with a low jitter master clock based upon a 12MHz VCXO from Tentlabs.

The best two features on this particular kit (aside from cost) are the asynchronous clocking that frees us of the sonic confines imposed by CPU and system loads at the USB end of things. Secondly, Doede does not rely on the USB bus to power any of the circuitry on the PCB. This leaves us with the chance to explore various low noise linear PSUs and batteries with relative ease. Either way, the sonic performance should be in excess of designs that rely solely on internal PC power. Also worthy of a mention here is that the I2S output allows us to try out various DAC kits in the future. For example, we could use the Doede kit solely to provide the USB to I2S conversion and proceed to add a separate I2S input DAC kit as an alternative to the TDA1543. This element of flexibility is especially important to me as I already have the outboard tube stage that I used to provide the audio zest from the Pioneer player. Most modern DAC chips available today feature balanced voltage or current outputs. In my case, a balanced voltage output DAC chip allows me to transplant the tube based audio output stage and enjoy its sonic merits at my leisure.

Doede's kit is available either pre-stuffed and ready to go, or with all of the thru-hole parts loose, leaving you to stuff the PCB and do the soldering. As the PCM2707 is an SMT device, it comes pre-mounted and pre-soldered regardless of the kit option you choose. I decided to purchase the kit without the thru-hole components soldered in, as I felt confident enough to tackle this element of construction myself. I must note that there are no part-by-part instructions supplied with the kit. However, basic instructions and pictures on the DDAC homepage are clear enough to provide a good point of reference should you wish to confirm device orientation or placement in some situations.

If you've never built or soldered a kit before you're best advised to go for the pre-built option at additional cost. Either way, you'll have to provide a suitable case to house the kit. Do make sure to buy a case large enough to house additional PCBs for discrete regulated power supplies or additional DAC boards should you get the bug to upgrade things later. Audio output from Doede's module is configurable via the TDA1543 or from the output of the PCM2707 chip itself. In either configuration, the audio performance is quite good, although the TDA1543 is clearly the better performer in most situations (there will be more subjective stuff later).

The Test System, Cont'd Twisted Pear Audio Opus
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  • Clauzii - Monday, December 1, 2008 - link

    .. I can recommend a Terratec Phase 22. No computernoise whatsoever. Pure, clean sound. I don't have a surroundsetup, but movies through this card sound brilliant, with a lot of detail and no digital 'fnitter-fnatter'.
  • Clauzii - Monday, December 1, 2008 - link

    Have to correct myself: With the card You can actually hear all the bad mixing of the movies themselves.
  • daar - Monday, December 1, 2008 - link

    Honestly, for a tech review site, I'm very disappointed that you nixed any pro sound cards and went for the audiophile kool-aid. Proper regulation and filtering can deliver clean enough juice for the best audio applications and while the USB option is kind of interesting, it creates more clutter, is more expensive, and the supposed better quality can't even be objectively tested.

    There wasn't even an attempt to build a measurement procedure, and while some sustain the notion that audio is beyond measurement, since when does AT throw out standard science and efficient engineering in favor of pseudoscience?

  • RobinBee - Monday, December 1, 2008 - link

    "Proper regulation and filtering"

    Yes. A good motherboard does this. And: A hi-fi sound card such as ASUS Xonar D2 (PCI bus) delivers »clean juice«, very much better than Creative's x-fi. And: A good case makes a pc rather quiet.
  • RagingDragon - Saturday, December 6, 2008 - link

    And a sufficiently powerful amp and/or headphones with good isolation make PC noise irrelevant.
  • Servant of Shodan - Monday, December 1, 2008 - link

    Not meaning any disrespect to the author - it was a good article - but I've notice a lot of camera reviews recently, and now a review about audiophile stuff... and it just seems so out of place for a PC enthusiast site.
    There are hundreds of credible sites for both cameras and stereos/speakers/amps/etc.; and I feel that it sort of muddies the waters here to have these types of articles, when there are other excellent places where they fit in perfectly.
    I come to Anandtech for computers. I think it should keep to that topic.
  • SpeedyVV - Monday, December 1, 2008 - link

    Holy cow, audiophiles i think are THX certifiable!!!

    Can you guys actually hear yourselves???

    All joking aside, I love music, and sound, and guitar tube amps, a nice hi-fi.

    But the stuff you guys talk about is way, WAY, beyond me ;-)

  • Boushh - Monday, December 1, 2008 - link

    DRC does realy work. Last year I exchanged my old SONY AV receiver for a new Denon AVR-3808 with Audyssey. With the SONY I was unable to get a good sound at my listning postion (specialy the rears never actually worked). And even though I had my reservations for things like Audyssey, I ran it on the Denon. And low and behold: Now I was in the middle of everything. I was realy amazed that taking some samples with a microphone could have such impressive results.

    The second thing: DAC's for computers. I recently saw that Cambridge Audio released a DAC for (among other things) computers (http://www.cambridgeaudio.com/summary.php?PID=320&...">http://www.cambridgeaudio.com/summary.php?PID=320&.... Maybe a good idea to compare that to the setup used in the article. It seems to me that instead of all those components it would (for the most of us) be alot easier if it was just in one box. But maybe that is just me :-)

    Anyway, nice article. It shows that people who are intrested in audio and are willing to do something for it are always on a never ending road B-)
  • strikeback03 - Monday, December 1, 2008 - link

    ... that this article shows that looks are not everything, as those drivers look like the cheap junk that comes in stock car systems.
  • jabber - Monday, December 1, 2008 - link

    They probably are! Remember in the world of 'high-end hi-fi' you build a component out of $20 worth of bits, stick a bit of varnish sanded wood on it then add on the 2000% 'hi-fi mug tax'.

    Its one of the best businesses to be in if you are unprincipled and lazy.

    Your customers are easy because they have invested so much money in their systems they are always open to fear and doubt about it. Easy prey!

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