Audiophile USB to PCM

The Waveterminal piece is interesting. It offers sample rate conversion. Maybe this is what is needed to take the signal from the computer to a home audio DAC and maybe that is what was missing from the M-Audio piece. Like Harry, I am no computer expert, I learn as much as I can in order to get the computer to do what I need, but my interest lies far more in music, which is the carrot that leads me to learn about computers. I am curious to find a product that will let me connect the computer to the digital input on my pre-amp so I can use the DAC in the Proceed, so I will be interested in hearing about Harry's experience with the Waveterminal piece. I the meantime, I am getting a real kick out of this G4, Apogee, Mackie system I've built. It is surprisingly accurate, musical, and enjoyable. But, this has opened up a little mystery and now I am curious to know whether uncompressed music files like AIFF need to be converted before they can be read by a home audio DAC and why my Apogee DAC doesn't need any conversion before it can perform its magic.

Rsbeck:

Thanks!! Do you think any or these converters are better or worse than each other?? There are lots of them; M-Audio, Edirol, Xitel, Apogee, Ego Systems, etc.

Also, I'm interested in the differences between streaming through a network as the SlimDevices Squeezebox does, and the hardwired devices listed above. I guess the real issue is what is going to provide the most bit accurate stream most effectively.

harry

Going back to basics, there is a bitstream on the CD and the idea is to feed that to a DAC to convert it to analog. PCM just (I believe) means pulse code modulation, which basically means communicating bits between two devices by an agreed upon standard for interpreting voltage pulses on the wire between them. USB is a serial interface, which means among other things (I think) that its buffered, so its a bit more hardware to implement than something translating pulses into TTL signals for digital processing. So, because coax digital is PCM, and USB is specific serial protocol, there is a conversion from a serial protocol to a different electrical format. Hopefully doesn't mean that the actual datastream of 1's and 0's is changing, but when I've got a box that is USB on one side and coax digital on the other, I call that a "converter."

Of course, I could be dead wrong. Its happened before. ; )

AIFF/WAV/MP3 is just a means for storing the bitstream on media. There is all sorts of stuff added to store things--directory records, sector sequence data, etc--even if you aren't doing any compression. But, with compression, you also need software to recover the original bitstream (or something that looks pretty close, if it was lossy compression).

I wonder, based on what you said, whether your M-Audio somehow ran the bitstream through a low end DAC and, if you used the digital out, ran it through an analog to digital converter. Doesn't seem to make much sense to me, but might explain the problems.

Sample rate conversion sounds sketchy to me in terms of rewards... Can't get more samples per second out than there are samples per second in. But, that is what oversampling is and that seems well beyond my technical competence. How does the thing *sound*? I guess the benefits of creating a 24/96 stream out of a 16/44 stream is going to depend heavily on the quality of what is doing the conversion...

Its actually "Eric," not "Ed." I should probably stick a response in that "where does your userID come from" thread. Every time I buy or sell something on A'gon, I get an email addressed to "Ed." *sigh*

Eric -- thanks for the info. Maybe it is even worse -- maybe the M-Audio converted the signal from digital to analogue and back to digital. Whatever it was, the Apogee sounds way better, but I know the Proceed has good DAC's, so I am pretty certain something went wrong inside the M-Audio piece. At some point, I am going to take an SPDiF out of the Apogee into the Proceed to compare them in that capacity.