A "bit" of information

Koestner, in my opinion, although some dacs claim superb jitter rejection, their ability to deal with certain amount of junk that comes in from the transport is important. I personally don't think that Benchmark DAC-1 or my Bel Canto DAC2 are so jitter immune. They probably are better in this regard than some other dacs, but again it all depends on how much of that junk that comes in they can deal with. Recklocking the signal could be affecting other aspects of the dac's performance, making overall impact on the sound. I think that the cleaner the signal from the transport, the better the dac's overall performance. Also, this is where a good digital cable comes in. I seem to agree with Rockvirgo
here, it's just like a lens on the camera. Better transmission of the signal, that's all. Just speaking from my experience, this is how I picture it.

I am an engineer, with 30 years digital design experience, so I'll be happy to give you the technical explanations:

1) The S/PDIF output from a transport is specified at 75 ohms characteristic impedance. This means that the output impedance of the transport should be 75 ohms and the input impedance of the DAC should be 75 ohms, as well as the connecting cable and connectors. Mismatches in this impedance can cause reflections that cause jitter, and these mismatches are quite common in even the best transports. I have measured and fixed plenty of them.

2) The slew-rate or rise-time of the S/PDIF digital signal has a large effect on the jitter when the signal is detected at the DAC. All transports have quite slow risetimes by design in order to pass FCC emissions testing with the poorest S/PDIF cable attached and mismatched impedance. Therefore, they cause unneccessary jitter. Some Transports will have slower risetimes than others, but unless they are modded, they are all slower than desired.

This white-paper I wrote details the analysis of why the cable length, impedance matching and risetime are all critical to minimizing jitter:
http://www.positive-feedback.com/Issue14/spdif.htm

Steve N.
Empirical Audio
Manufacturer/modder

Rockvirgo makes an important point. This is why computer audio is intrinsically better than CD playback. The pits are jittery as written on the disk. The Transport also adds jitter when it reads these pits, because each read head has different accuracy of reading the pits. When a pit is actually detected on an inside track and on an outside track probably varies from one transport to the next.

Steve N.
Empirical Audio
Manufacturer/modder

Thank you all for your responses. I was trying to convince myself that I didn't need a new transport. I've been told my Sony DVP S900es is not good as a transport.

"This is why computer audio is intrinsically better than CD playback. The pits are jittery as written on the disk. The Transport also adds jitter when it reads these pits, because each read head has different accuracy of reading the pits."

And the cheap CD drives in PCs don't add jitter when they
read the data on to the HD, and the noisy PC PSU doesn't effect the output signal?