2. pc-audio
  3. 1147036039

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.

Thanks,

Matt
descartes

Showing 9 responses by audioengr

audioengr
3,282 posts
 
Pabelson wrote:
"Reclocking is part of the DAC's job. If you have a DAC that does not reclock, you have a defective DAC."

Sorry, not true. Only upsampling DAC's actually need any sort of local clock. The clock is usually recovered from the S/PDIF signal by a receiver chip or comes free if it is an I2S interface.

Steve N.
Empirical Audio
Manufacturer/Modder
audioengr
3,282 posts
 
Sfar - If you heard the same AirPort Express with a Coaxial S/PDIF interface and a Superclock3 in the AE you would be shocked at how much better it is than the stock AE with Toslink interface. Not only as good as your transport, but better.

The Same AE with Superclock3 and I2S interface (possible) would be incredibly good.

BTW - Apple Lossless, like most lossless compression algorithms is identical sounding to .wav or uncompressed.

Steve N.
Empirical Audio
Manufacturer/Modder
audioengr
3,282 posts
 
Herman - here is a white-paper I wrote on jitter and computer-driven audio:
http://www.positive-feedback.com/Issue22/nugent.htm
audioengr
3,282 posts
 
Glass-fiber is certainly better. I have tried this with a stock AE as well. I have sold some AE upgrades, with Superclock3, new power supply and S/PDIF coax interface, and the customers seem to love them. I have designed a board to add I2S interface to the AE as well, but I have not fabricated any yet, too busy. I already have an I2S interface for the Benchmark DAC-1. The combo of AE with I2S and DAC-1 with I2S would be killer. I guess I'll have to get this done...

Steve N.
Empirical Audio
Manufacturer/Modder
audioengr
3,282 posts
 
Pabelson - You are correct, some DAC's, such as the Benchmark DAC-1 will reduce the jitter from the Toslink of an AE, but most of them do a fairly poor job of this. Even the DAC-1 sounds different with different digital sources. The theory behind the Lavry DAC's is the best I have seen. This will actually work if implemented well. The best solution currently is to make the jitter very low in the AE, which is what I try to do. An I2S interface and a Superclock3 accomplishes this.

Steve N.
Empirical Audio
Manufacturer/Modder
audioengr
3,282 posts
 
"Did the Creative Audigy 2 NX turn out to be asynchronous? I am guessing not as you have chosen others to modify."

No. I believe it is. It was just more difficult to mod and make into a product, besides it was discontinued as all of the other decent solutions were (Edirol UA-5, Waveterminal etc..) The transit lives on and they have no plans to discontinue it. I wil not be modding them for long anyway, as I have my own design ready to go. It will still use the M-Audio drivers and ASIO as they sound the best for PC IMO. The only upsampler that I use is Secret Rabbit Code, which I have licensed. It is better than 44.1 every time I try it.

As for the quote above, I suggest that John Swenson and Gordon resolve this. They both know more than I do about USB interfaces.

I was impressed with the Lavry DAC technology. HAve not heard one yet though...

Steve N.
audioengr
3,282 posts
 
For those that want wireless USB (the best), Belkin has announced the CableFree USB hub and dongle, which replaces wired USB with Ultrawideband, high-bandwith wireless USB. The dongle plugs into your computer or laptop and the hub goes next you your USB converter or USB DAC and uses a short USB cable. Replaces USB 2.0. Demonstrated at 2006 CES in Jan.. Latest is that they are shipping in July. Pricing expected to be under $150.00. The advantage is that you can use ANY player software with this, unlike iTunes for AirPort Express or SlimServer for Squeezebox, and it will pass 24/96!!!
audioengr
3,282 posts
 
Can't find any info on the range.

Steve N.
audioengr
3,282 posts
 
Cable-free from Belkin is still not available. Last I read it was November 2006.

steve N.
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