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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  • goinginstyle - Wednesday, December 3, 2008 - link

    I agree, while I might argue about some of the conclusions or have a different opinion, the author knows what the hell he is talking about. It is obvious from a lot of the comments that people stopped reading on page two and brought out the guns. It is fine to agree to disagree but some the comments here apparently came from five year olds and not adults. Sound quality is subjective, get over it. I appreciate a different opinion than my own and found the article to be thought provoking at times. Something an article should do when covering a hot topic like audio quality. Being an old hippie myself, I still love the tubes but digital has its place now. I vote that he does another article on this subject and lets see where AnandTech takes this in the future.
  • strikeback03 - Tuesday, December 2, 2008 - link

    How do you live in a rural area and not own a car?
  • royboy66 - Tuesday, December 2, 2008 - link

    hi I have been into audio and music for many years it is my hobby, computers are my business and hobby. I commend you guys for covering this topic -i will download the software you have used and give it a try.
  • Wastral - Tuesday, December 2, 2008 - link

    Well at least he talked about SOMETHING to do with the PC!

    DAC talk was good if really really wordy. Nothing like breaking points down into something someone can read.

    Not one review of sound cards of sending analog output out from the computer and its actual quality... You know the main component needed in a PC... What a stooge.

    Most People can't even hear over 16khz and the very rare person can hear around 20khz. I tested out at 18.3khz with a wave generator when I was 16. Now? Probably no more than 14khz at the age of 30. Not to mention the dB sensitivity of the ear over 16khz is next to nothing. On top of that, as I pointed out with a little thing called age your hearing decreases to 10khz by age 60 or so.

    Of course If we really want this right, it has to be decoded at the amp, which won't happen, due to there being a million and 1 codecs around. Thus, we are stuck with analog.

    Its all about your speakers and amp. That part of his article I won't complain about too loudly.

    Just his BS about tube amplifiers. 10 years ago that was true. Now its only because old Hippies are retiring and tube amps were top of the line then and they have too much money and time on their hands to burn, with nostalgia hot in their blood.

    Try recording something and then play it back with a tube amp or a Digital amp and compare the sound. No one uses Tube amps in studios. Why? Because it CHANGES THE MUSIC and is not as PURE as one can get with Digital amplifiers. They say they like it... wonderful, its not as true of a sound though, the HYPOCRITS!!!

    Everything else was typical Audiophile BS ignorance. Hell, I have even installed an outlet for an "audiophile" pointed North-South for better "power" to his amp. No joke, he whipped out a compass.

    Comments like, "I only use silver 24 guage wire." DUMB shit!! Go another guage larger in copper is a hell of a lot cheeper and gets better results.... IDIOT. Not to mention its your CONNECTORS THAT COUNT.

  • Rajinder Gill - Tuesday, December 2, 2008 - link

    Where did I sue the word 'only' in that statement about wire?

    Seems you've done the typical thing and read what you want to read.

    My entire cable setup costs less than $40, including the interconnects and mains cables. No north-south compass in my house either.

    Connections are direct soldered where they can be and if it's practical enough. No expensive connectors used.

    I'll aslo refrain from using the derogatory language you seem so comfortable with.
  • Rajinder Gill - Tuesday, December 2, 2008 - link

    correction meant 'use'..
  • Geraldo8022 - Tuesday, December 2, 2008 - link

    Mr Gill is trying to do some of you a favor by cluing you in, but some of the denser posters come back with talk about receivers, headphones, soundcards, measurements, double blind testing, Class D, etc.
    Someone once asked Satchmo what jazz was and his reply was, "if you gotta ask you don't get to know." I guess some of you here aren't gonna get to know. Just keep your head in the sand, or elsewhere.
    I have been into HiFi for almost forty years and it is about things like sitting in the dark at one o'clock in the morning with Sarah Vaughn. If that doesn't make any sense to you, then you don't get to know.
    Mr Gill, I thank you for this article. You keep on keepin' on.
  • Beefmeister - Tuesday, December 2, 2008 - link

    Great choice on the Opus DAC; the Twisted Pear Audio guys do great work. I've built myself a Buffalo DAC.

    That being said, I would strongly suggest you look at replacing your Ballsie with IVY modules. IVY is capable of zeroing the DC offset from the DAC, thus allowing you to jumper the output coupling caps on the Opus. It also gets rid of the dual and quad OPAMPs of the Ballsie, which apparently don't measure as good as the single and dual variants.
  • draak13 - Monday, December 1, 2008 - link

    Starting off with reading the article, I was getting quite pissed about how much this was going into the usual audiophile BS, where their 'prowess' of electronics goes so far as, "the resistor says 1000 ohms, but really, it TASTES like 992 ohms. There's such a huge difference." I was half expecting there to be talk of putting sandbags around the room to 'enhance the musical quality of the room setting.'

    Reading further, I found that this article was quite good, and was even moderately scientific as I have come to expect from Anandtech. The choice of the recording microphone was EXCELLENT; I looked up the spec sheet for that, and the response on that mic is absolutely incredible, and is a total steal for the price you pay. Kudos to anandtech for finding and using it. The very objective comparisons of two different dacs was quite excellent, as were the multiple recordings.

    I absolutely loved your analysis of an addition of a subwoofer into the system to compensate for the range of the main speakers. I have always been curious about how well that would actually work. Lastly, I was blown away by your DRC analysis. That's an INCREDIBLE algorithm that you have there; I love it.

    There are a few things that I could say about the choice of components, and the squabbling going on about what components "perform better", but there is an end-all test that you could do to prove what is and isn't BS. First, I can flat out GUARANTEE you that your microphone is as sensitive or more sensitive than the human ear AT LISTENING VOLUME. That is, anything that you can hear, that microphone should be able to hear as well. So, if you wanted to turn your subjective listening tests into objective listening tests, then play back those songs you were testing your setup with, but record those songs at listening position with your microphone using all of your different setups. Record them multiple times, as you have been doing in your tests. Next, using MATLAB or whatever other software, overlay the recorded waveforms and determine the differences between the two. If there truly is a difference between the different hardware setups that you were using, I guarantee that this will be sensitive enough to detect that difference, and will do so quantitatively.
  • DeepThought86 - Monday, December 1, 2008 - link

    At the end of the day, is all this expensive tomfoolery just to listen to music? Why pay extra and turn your brain to jelly to boot?

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