The basics of PC audio

Some questions for you:

Assuming you have the PCU (in my case, a Mac Mini) near the stereo, with a USB DAC coming out of that into the preamp (or do you have it configured some other way?):

a) What does one do with the monitor--perhaps run an extra long cord and put it away from the system to keep the RF from feeding into the audio?

b) Can the CPU be placed far enough from the preamp to where RF from it won't affect the sound of the system?

c) What about using Apple AirPort Express and AirTunes and running a USB DAC out of that into the preamp; are there any advantages/disadvantages to that sonically vs. having the CPU feeding directly into the DAC?

d) Suppose you buy music from the iTunes store in MP3 form. Can it be converted to aiff or some other "lossless" format such that you'll wind up with a high quality file? Or does the fact that it was already converted to MP3 doom it to sonic mediocrity?

e) How quickly are USB DACs improving in quality? I don't want to buy a DAC and have it be obselete the next year.

I appreciate your answers.


a) and b) I don't think RF interference is a concern with most systems

c) I'm almost positive that the USB port from the AirPort Express is not compatible with a USB DAC

d) once a file is compressed with a lossy format such as mp3 it can never be converted back

e) things constantly improve but the USB DAC is a mature format. It is basically the same DAC that has been around for 20 years with a slightly different interface to accept the digital data via USB rather than spdif.
a) Interference is a very local phenomenon. There's no way to know what will be necessary in your situation. But interference is also far less of a problem than you might imagine. (Think how many TV monitors are adjacent to preamps in home theaters.)

b) Ditto. Probably won't be a problem, but you never know till you try.

c) A wireless network is inherently less stable than a wired one. Cordless phones and microwaves can interfere with the connection. If you go the Express route, I'd connect a standard audio DAC to the audio out, rather than using a USB DAC. But sonically, it's probably a horse apiece in general, though specific set-up issues might be a factor.

d) You can convert an iTunes file (which is AAC, not MP3) to an AIFF file, but it won't be any better than the AAC file. Once a file is compressed with a lossy codec, there is no getting back the information that's lost. OTOH, mediocrity is in the ear of the beholder. For critical listening, you'd want full-resolution digital files (AIFF, WAV, or a lossless codec). But for casual or background use, you aren't going to notice that it's "only an MP3."

e) I don't know the USB DAC market well, but the only thing I'd worry about is noise. Assuming you can get adequate S/N from today's models, future improvements will be marginal.
I appreciate the responses. I hadn't realized that there's no going back from an MP3; though now that I think about it, it's very reasonable. Given that all I have are MP3s right now (and I have lots of them), the DAC on Airport Express should be more than adequate, I should think? Or, perhaps even the DAC in my laptop via the headphone jack would be adequate?

Thanks again,

d) Pabelson is corect, when I said it could not be converted back what I meant to say was that the information lost could not be recovered, but it can be converted to other formats.

I'd connect a standard audio DAC to the audio out, rather than using a USB DAC.

??? If you use the audio outs from the express you don't need a DAC. The express USB port is for a printer and won't work with a DAC anyway.