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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  • ccd - Thursday, December 4, 2008 - link

    If you want to be scientific, there is no substitute for double blind testing. It's as simple as that. The human psyche is just too susceptible to suggestion.

    I have been in stores and compared components. But as you should know, all sorts of games can be played with equipment. A common trick is connecting a speaker to a monster amp which makes it sound better. The other key to speakers placement. You can take a speaker that sounds great in the store and sounds crappy when you get home because the listening conditions are so different.

    The most eye opening experience I ever had was taking a home made speaker into a very high end store at the end of the day because on of the salesmen wanted to listen to the transducer I was using. The speaker which also used one made speaker wires out-performed speakers costing over $20,000! The Orions that I have mentioned in previous posts are better than this speaker and the Orion uses electronics which are hardly out of the ordinary. I would put that speaker up against anything, regardless of price. Listen to a speaker like the Orion and you will realize that "high end" audio is mostly snake oil.
  • goshwan - Thursday, December 4, 2008 - link

    Why should we take your 'subjective' (because that is what it is) opinion that the Orion's are that good? How is your opinion any different from when the author says his speakers or DAC's are great?
    Have you heard these components yourself? Have you heard any of the components used in the review?

    Humans are subjective animals and purchaing decisions usually involve sprinklings of logic and subjective preferences. Audio is one of the best examples of this. Even solid state amps sound different depending on topology and operating class. Your statment about monster amps reflects this. They indeed sound different.

    I have heard the TDA1543 on occasion, but I would not be foolish enough to think that every other DAC sounds the same.

    Granted, the Orion's are a indeed a fine speaker based on reports, but it's also possible the ones we see used in the article are too.

    To mee it seems as if everyone is forcing their own subjective opinion in reply. Some are objective, but theirs plenty of subjective, which is funny really.

    I think the article could have offered some more objective stuff. but at the same time, the listening conclusions of both DAC's were pretty much spot on. The TDA1543 is known to sound soft at hf sounds, especially in nonos. The room correction stuff really was great. In fact, I wonder how many readers got that far before exploding their thoughts via the keyboard.

    You have some interesting points on blind tests, arguments for and against seem to rage the web over. I wonder what people would accept though, how much evidence would be needed if something turned out to be spot on?

    I'm interested to see where AT go with the audio stuff.
  • ccd - Saturday, December 6, 2008 - link

    I guess we will have to agree to disagree. Moving right along, I do not have any issues with open baffle speakers. I'm not a techie, but there are theoretical advantages to open baffle speakers. The trick is getting the baffle wide enough so that the baffle simulates the driver being in a wall. The problem with open baffle speakers has been aesthetics, as an open baffle speaker usually have to be very wide. I've seen open baffle speakers with hinged sides to the speaker need not be really wide except in use. The test speaker uses clear sides which would limit the impression of width.

    Actually, my issue with the speaker is that it is full range. I have not heard this speaker, but full range speakers generally have really nice mid ranges and suffer in both the upper range and lower range. I do like that he paired his speaker with a sub. However, full range speakers usually need a crossover at a high frequency than I would like and the higher the crossover, the trickier the integration. In case you haven't guessed, I've hung around DIY circles for a number of years, though not recently.
  • goshwan - Saturday, December 6, 2008 - link

    Well seeing as neither of us have heard the speaker in question it's a subjective assessment. Of course, individual drivers tailor made for the frequency range in question should be more proficient. Given that we hear little over 15Khz though, I bet they sound pretty cohesive. Yes higher range crossover integration does become an issue, but if one is not needed 'subjectively' then why bother?
  • ccd - Saturday, December 6, 2008 - link

    The speaker used in the article could be good, very good for all I know. Since I have not heard it, I can only talk in generalities. The tradeoff is between a full range transducer with no crossovers and a frequency response that is not nearly as flat as a multi-driver speaker with crossover points. Neither speaker is perfect.

    Full range drivers, at their best, have gorgeous mid-range performance which is highly valued by those who favor them. The tradeoff is a fall off in the upper and lower ranges. The limits of human hearing help cover the failings in the upper ranges and there are tricks like the use of transmission lines to extend the lower range, but there are limits.

    The multi-driver speaker has a different set of issues. One is finding drivers that complement each other. Merely matching frequency response is not enough. The other is determining the right crossover points and slopes. Not a problem for an expert, a great challenge for the amateur. From what I have personally heard and from what I know about speaker design, a well designed multi-way speaker, particularly hybrid active (passive crossover between the tweeter and mid-range and active between mid-range and woofer is just a better solution than a single full range driver. Right now, I'm sitting in front of a speaker with one of the widest frequency ranges of any driver and it is still a 3-way design.

    Again, I have not heard the speaker in question. But I also know it is VERY hard to overcome the limitations that come with certain design choices.
  • goshwan - Saturday, December 6, 2008 - link

    That's the beauty of audio, final choices are often based upon what you favor. There is no one speaker that will appeal to all tastes. Which is why I don't diss on people going one way or the other. The calculated final response with sub and DRC was pretty flat. Impressive.

  • ccd - Thursday, December 4, 2008 - link

    This gets back to my original post on this article. A lot of this is very subjective and there will never be any agreement on it. IMHO, things like DAC reviews should not be a part of this site, it would not matter whether I had heard the components or not. However, the DRC part should definitely be featured on this site and was great.

    BTW, I used the Orion as an example of a kit speaker which is both generally regarded as one of the best kit speakers available and one whose design runs counter to many of the assumptions made by this author. I encourage you to listen to the speaker and come to your own conclusions.

    Double blind testing is the only way I know of to accurately determine whether equipment changes actually make a difference. It is opposed by many in the high end because they don't like what double blind testing tells us: much of what they tout just doesn't make an audible difference.
  • goshwan - Thursday, December 4, 2008 - link

    I 'subjectively' disagree, the DAC kits are designed to run off the USB bus. Tha means a computer is involved.

    I don't follow your 'assumption' accusations either, like yours the opinions stated are subjective. Linkwitz backs his up on his site true, but the adoption still involves approval by human ear - not just visionary acceptance of theory. That means verbal expression in the form of words which you too have used to encourage people to listen to the Orions. I have no doubts those speakers sound great. But I have heard great things about open baffle speakers too.

    I agree with you on this, in that guess we can agree to disagree.

  • Flyboy27 - Wednesday, December 3, 2008 - link

    How much energy do you have to put into a system before you can actually start enjoying your music. I realized many years ago that I just needed to listen to my music instead of worrying so much about sound fidelity. Since then my enjoyment of music has increased so much. I am a musician, have been trained as a recording engineer, and work in the music industry. There comes a point when you have to stop worrying about your gear and just enjoy your music.

    Having said that it is a shame that so many people listen to 128kbps mp3s. I'm planning on re-ripping my entire CD library in a lossless format. This is part of the reason for me why it is so important to have a physical copy of my music. I'm not "stuck" with a low bitrate crapy itunes copy.
  • kompulsive - Wednesday, December 3, 2008 - link

    You guys should definitely check out the M-Audio Audiophile 192 or Audiophile 2496 depending on your needs. I've been using these and similar products for years in my small studio at home and the price, quality, and value are superb. I think Creative products are grossly overrated and overpriced.

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