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).
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mindless1 - Monday, December 1, 2008 - link
The fact is, even audio streams that measure the same can and do still sound different. The problem is the resolution of measurement and the misconceived notion that the brain interprets sound at a fixed interval as measured.There's a lot of snake oil in the audiophile world, but there's also a lot of what you'd like to call "magic" only be cause you don't accept it as non-magic.
Any decent DAC would in idealized theory be as good, but in practice a different IC topology may lend itself better to certain inherant localized noise frequencies and cutoffs, be better mated to the circuit it's dropped into, have drifts from thermal changes, etc. If they were all the same why would there be so many? I will agree that which modern DAC is used in a reasonably good design matters less than what follows after it in the chain but the best way to minimize any potential for degradation is to start out with what is most likely to minimize it in every way possible then following this concept the entire time, waiting and seeing if the end result is audibly different rather than downplaying them all without knowing the additive result yet.
CSMR - Monday, December 1, 2008 - link
Yes if you are maximizing quality you will choose the best of all components. But it's more sensible to care about cost and time too, so you have to prioritize. The value of the research about the unimportance of DACs (at at beyond a certain level) is that you can stop worrying about this part of the chain and spend you time/money where it is important.JonnyDough - Tuesday, December 2, 2008 - link
Exactly my point. Why spend more on one component if it's going to be "bottlenecked" by another one. Spending $2000 on a nice amp is crazy if your other components are crap. I think in the end it's like all other techs. You want decent stuff for a reasonable price unless you have more money than brains. While I scoff at people willing to spend more than few thousand on a sound system, without them we wouldn't have gotten to where we are today - with good possibilities on the market. As long as you like what you hear, who cares if it's perfect? At one point is something "good enough?" I mean honestly, there are people starving in the world, friends dying of cancer, etc...and we want to worry about whether or not something is inaudibly "perfect." Blow your money on something that MATTERS, you can't listen to music every hour of everyday unless your job is singing.CSMR - Tuesday, December 2, 2008 - link
I meant you can spend time/money on speakers/room acoustics/dsp but food for starving people is admittedly a better use of time and money.JonnyDough - Wednesday, December 3, 2008 - link
That's actually a matter of perspective. For example, you can donate food to a starving kid in some third world country and next thing you know that child has three kids and no way to feed them - and you've just marginally made the problem worse, not better.I think money is better spent on education, which leads to fewer babies. Many countries do not have quality farmland that can support the population on their own (the U.S. supports a large percentage of the world's population). Then there's natural habitat destruction, pollution from oil for having to ship food to them, etc. You get the picture.
JonnyDough - Monday, December 1, 2008 - link
While I was generally agreeing with CMSR above, I guess what everyone ends up saying is that hearing is subjective, which is something audiophiles are always agreeing upon yet they still love to argue over things.Does a vinyl record produce better sound than a CD?
It depends on what an individual values most.
A CD may produce less static noise, but have a "duller" sound, seemingly less highs and lows. It all depends on what one appreciates with their own ears.
While there are measurements that can be taken in a closed chamber, one sound system might actually sound better in a specific home or room than another for whatever reason. Even so, the average person can rarely tell a difference these days between the moderately priced components.
The really silly thing is that people will spend $200 on a sound card and then use cheap plastic speakers.
Rajinder Gill - Monday, December 1, 2008 - link
Lol, it's ok, everyone in entitled to have their say.It's the first piece so bear with us while we try to cater to a wider set of ideals.
With regards to the obj/subj stuff, it's an argument that'll never be solved.
later
CSMR - Monday, December 1, 2008 - link
Sorry if I came on too strongly; I was just expecting that Anandtech would have not necessarily an expert take but at least a more technical take than you get in audiophile communities.I would do some more fundamental thinking about what are the key factors in computer audio playback.
As a start you could rank in terms of what is most critical:
computer performance, computer quietness, software (drivers, dsp), analog line out, volume control, amplification, cables, speakers, room acoustics.
I won't give you my list but you should think about it and it is possible to compare many of these things in a very quantitative way, and some are more important than others by several orders of magnitude.
AnnihilatorX - Monday, December 1, 2008 - link
A dumb question about correction.The theory behind it is simple enough, but why do we need dedicated hardware to do the correction? Why can't we use simple graphical equalizers? I understand graphical equalizers are quite discrete in the range of selectable frequencies. How much difference does it make?
Rajinder Gill - Monday, December 1, 2008 - link
DRC - ease of use and range of control, plus taking care of things in the digital realm rather than in the analogue.You could fudge some control with a multi band digital equaliser and the means to measure the response, but it'd be damn tedious and utimately limited.