What is your opinion on the stereophile J-test?
It measures analog out of a DAC to a test signal - so it checks for both incoming and intrinsc jitter.
Much better to measure the jitter directly, although this is all you can do if the Master Clock interface is inside the DAC. Mildly interesting and only gives you part of the picture IMO because the stimulus is not a true music waveform.
What do you think of the typical SOTA DACs that have a noise floor at -150dB when tested for jitter?
Those are good numbers, but what stimulus is used? A single frequency? Not good enough.
How can perfect performance be improved upon and what do you look for when testing an asynchronous DAC of this level and how could Synchro-mesh or another cable improve upon perfect?
I have yet to see or hear "perfect performance". Every time I make an improvement to my own DAC or converter, I think that it cannot possibly get better, but then it does. If I had to choose the best DAC for a demonstration, cost no object, I would choose mine, even though it's not the most expensive or even DSD capable.
Performance can always be improved. If you can drive this DAC with S/PDIF signal and hear a difference with different cables, then it is not jitter immune. A simple test. The Synchro-Mesh and a reference BNC cable would likely improve the SQ from it.
If it is an internal Ethernet or USB interface, making changes to the power delivery to the clock circuits and buffers will likely improve it. Sometimes even making changes to the ground-plane or voltage regulators will improve it. Performance in high-end audio is mostly about good power delivery, which includes optimum board design, power supply, regulators and decoupling caps.
I modded DACs and other digital gear for 10 years and I was able to improve any product a customer would send me. This is precisely what gave me the bag of tricks that I use on my own products. Given enough time tinkering, I can probably improve them even more too.
Steve N.
