Originally Posted by krabapple
Why do you assume
the noise of the PC -- noise in the soundcard output, really -- was high enough to be a problem?
Actually, the PC's sound card was not used. The testers provided their own DACs, amp, and speaker or headphones. The authors provided a PC and interface to the DAC using whatever output the DAC box required. I have measured jitter from PC busses to range from perhaps 100's of ps to well into the ns region, but have not measured them recently (might be an interesting thing to try in the lab). I do not know the specs of the interfaces they used between PC and DAC, nor the PC they used (the names etc. not stated in the paper). So, properly speaking, I assumed
there was insufficient information in the paper to properly validate the tests. Nor do I know that they are invalid
(throwing out the baby with the bath water), but in any event they do not address the original question I had about correlated vs. coherent/deterministic jitter levels, either present at the DAC's clock input or their threshold of audibility. In another thread the point was made that, for such low levels of jitter (few ns), it is unlikely that anyone could hear it if it were correlated or not, a valid point.
Honestly, for me this falls deep into the "sorry I asked" category. I was curious and hoped to get an answer, not start (continue) a huge squabble or get embroiled in semantics. There are obviously people with ears far more golden than mine, and credentials far greater than I'll ever have in this area, on both sides of the fence. I plan to sit on the sidelines (obviously not my strong suit) and continue to follow up the reading material various folk have provided before I get thrown off this board. Or perhaps that would be best...
I am tempted to sign off with a tag a friend uses" "Have a nice day, unless you've made other plans". It's clearly time for me to bow out.
Besides, I've got a foot of snow to shovel so my wife can get back in the garage when she gets home from work (spring in the Rockies).
G'day - Don