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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Christobevii3 - Monday, December 1, 2008 - link
What about using a dts/ddl sound card to output to a basic receiver?Rajinder Gill - Monday, December 1, 2008 - link
If going to the nth degree for 2 channel it’s hard to look past USB-I2S in async. For multichannel, a DTS/DDL card is perfectly adequate. Although I’d still use an external solution if I could find one.wolrah - Monday, December 1, 2008 - link
How do you figure I2S is any better than S/PDIF? S/PDIF supports up to 20 bit resolution at either 48 or 44.1 KHz, so it can carry a CD audio stream natively. The bits on the disc are the bits flowing out the optical port on the back of your gear of choice.In theory an I2S signal will be able to take more interference, but when we're talking optical signals in a home environment the kind of interference needed to make a difference would be on the scale that you'd never be able to listen to anything.
Goty - Monday, December 1, 2008 - link
Well that's easy to answer:Nope. I'll stick with my Martin Logans, tyvm.
wolrah - Monday, December 1, 2008 - link
In fact it easily can, because plain and simple reading from the disc itself is error prone. A one time rip to WAV or [lossless format of your choice] using cdparanoia on its insane mode output through a high quality sound card will be the same as or better than any silly 4 digit CD player.Even playing straight off the disc, there's no reason to believe any "audiophile" gear will play a CD any better than any other CD player unless there's a design flaw like a crappy power supply.
On the note of power supply, am I the only one who laughed at the bit about the battery vs. the wall wart? Who wants to bet that he's never double-blind tested that one. That's the wonderful thing with A/V gear snake oil, it's very easy to hear what you want to hear.
mindless1 - Monday, December 1, 2008 - link
I've hand-built amps for years and double-blind tested batteries and wall warts. Yes there is a difference. A good (read: overkill for anyone not into building audiophile equipment) localized power filter stage, if not localized regulation, would ideally negate the difference between the two power sources but that can also unnecessarily increase the build complexity, time, and cost.PS the battery is almost always inferior assuming the wart has proper shielding or is inadequate in capacity, and generally I refer to a wart as only a transformer and rectification stage, not trying to build an entire high precision linear regulation stage inside of it due to limited space and EMI.
Rajinder Gill - Monday, December 1, 2008 - link
Martin Logan makes electrostatic loudspeakers if I recall.I'm not sure where that fits into using a PC as a transport and for DRC. Unless you're refering to the approval of open baffle design loudspeakers using te supravox drivers?plonk420 - Monday, December 1, 2008 - link
this is surreal...my $20 Chaintech AV-710 just died in the last 48 hours. i've been trying to resist the Head-Fi audiophile talk and try to find cooler heads to verify whether or not i should go X-Fi or DAC (something silly looking like the HotAudio HotUSB1 or Silverstone), or try to figure out if i'm experiencing the placebo effect "falling back upon" my ALC883, which i can swear "doesn't sound as good" EVEN THOUGH i'm fully aware of the power of placebo.
i'm not sure i liked the mixed bag of positive and negative reports on (cheap) X-Fi vs Xonar vs X-Fi USB vs some DAC vs E-Mu 0404/0202
mindless1 - Monday, December 1, 2008 - link
Choose a Creative card for gaming sound effects. Choose a DIY DAC for highest audio quality at a reasonable price. Buying some cheap commodity grade DAC is a gamble, I'm not familiar with those two products you mentioned but generally in the consumer segment and price range you end up buying an idea, a type of tech but not excellence in that execution.MOtherboard integrated audio usually doesn't sound as good including one using ALC883, though someone with poor hearing or gear may notice the difference less and less depending on where the weakest link in the chain is and how bad it is.
Gannon - Monday, December 1, 2008 - link
I have an X-Fi and it's better then my audigy, mind you I got the more expensive version with front panel and the remote. I use it for everything and have never had a problem, though I don't use vista at all just XP.