Hard Drive based system

Read this white-paper that I wrote that just got published on positive-feedback.com:
http://www.positive-feedback.com/Issue22/nugent.htm

Ecruz,

As Pardales and Audioengr point out - there's much to be
said for a server based system.

What you want the digital components ahead of the DAC to do
is to deliver the digital data accurately, and with good
timing - i.e. minimal "jitter".

One of the problems with many, if not most CD players is that
the transport is the "master" as far as timing is concerned.
That is - the timing information is part of the signal
passed to the DAC.

What you really want is to have the DAC be the master, and
follow its own clock. The better CD players and CD/DAC
combos follow this strategy with the DAC as the timing
master.

Disk based systems are naturally this way - in computers,
the CPU or the bus controller has always been the master.
Disk drives were never masters - so a disk based system
forces you into the DAC master model.

Dr. Gregory Greenman
Physicist

I can't quite follow Dr. Greenman's reasoning.

Basically, if the DAC reclocks, the clock in the DAC takes over. If the DAC does not reclock, it takes the timing info from the digital input. This aspect has nothing to do with whether the input is hard drive based or not.

The issue here is that the bit-perfectness and the quality of timing/jitter can be of very high quality even from a relatively low cost hard drive based system, especially when high quality USB to SPDIF converters are used.

From what I've read the Waveterminal is hard to come by now, if not completely discontinued. So what are some other high quality USB to SPDIF converters for Mac/iTunes? I don't need anything fancy, just a USB in and a coax out.

Morbius is correct, if the master clock is local to the DAC chip itself, then the jitter will be minimized. This is not necessarily the case with external "bit clocks" that a few DAC's and CD players utilize. This is often more difficult than it seems at first blush. The master clock must generate several clocks or at least a very high-frequency clock from DAC to transport. Some of the transport chips may use the higher frequency clock, such as 16.9344 MHz. The analogy to the disk-based system doesn't hold water though, IMO.