Is this a reasonable Audiophile Mac-based Server?

Restock's experiment is inconclusive. When you have multiple variables in an experiment it is impossible to determine which causes the effect. The conclusion that USB is better than toslink ignores the fact the transporter may be introducing large amounts of jitter. This may be the cause of the inferior sound and may have nothing to do with toslink. A better comparison would be

1. Mac Mini feeding Benchmark DAC1 via USB
2. Mac Mini feeding Benchmark DAC1 via toslink

even though this isn't conclusive either since despite what Benchmark says the DAC may indeed work better with USB. This isn't saying USB beats toslink every time, only that the Benchmark may be better with USB.

All I can say is that in my system ....XP computer - wireless - Airport Express - toslink - Altmann DAC the sound is fabulous, jaw dropping, stunning, ..(insert your own adjective here)

Amazing all the conjecture against Wireless 802 system and in preference for USB.....IMHO both should sound indistinguishable provided you buy modestly good gear...after all none of this is rocket science...do we really suspect manufacurers are all inept and incapable of building something that works.

What happens at the clock in the DAC itself is anyone's guess in a specific setup with your house mains power and whatever other applicances you have connected - but rest assured that most manufacturers are building perfectly good gear. There is no reason to be assuming the worst from teh outset until you find a problem. There is no cause for such fears from the outset.

As for me, I would build it and then cross check it against a CD player direct into the amp (using exactly the same test tracks as on iTunes) - that is what I have always done in the past (switching back and forth with the remote endlessly until I am satisfied I have no idea which one is which). If you can't hear any difference after this kind of extensive auditioning then it is good enough to stop worrying (just make sure to precisely level match volumes as even a very slight increase in loudness sounds better)

Herman, the experiment you describe was the first one I did when I got the DAC1 a while ago (I started out with a Airport Express and a Macbook with optical out)...

A better comparison would be

1. Mac Mini feeding Benchmark DAC1 via USB
2. Mac Mini feeding Benchmark DAC1 via toslink

even though this isn't conclusive either since despite what Benchmark says the DAC may indeed work better with USB. This isn't saying USB beats toslink every time, only that the Benchmark may be better with USB.

The differences between 1) and 2) were similar to the more recent experiment but even more pronounced. Similarly for the Airport Express which I also have. In fact, I was expecting the transport to do much better since it is isolated from the PC, but I guess that is not necessarily the case.

Certainly the observations are true for the Benchmark, which is the DAC Henry was considering. In fact, your experiments with the Altman are more of a singular experience, since Altman put great care in the toslink interface ;)

Also just to ad some information to the above experiments: I used a Glass toslink with a mini to regular toslink adaptor which works better than the Monster plastic optical fiber cable (as determined in previous trials.

Restock, maybe I missed it but I don't see where you used anything but a jittery optical out compared to the USB.