Originally Posted by bigshot
Jitter in the levels it occurs in even the least expensive audio gear does not affect sound quality. Not audible.
I don't have any sources to cite or evidence, but I wouldn't be so sure of that, particularly if you phrase it as "audio gear." Maybe we're thinking of different things? Are you thinking on the level of cheap CD players, iDevices, etc.? Or anything like a computer, phone, whatever would be used for music playback? How about really junky integrated audio systems for those cards that play recorded messages, a GPS device, whatever?
But anyhow, I think the point is that nobody yet seems to have proved jitter audibility at levels close to that of modern low-end dedicated consumer playback gear. That said, isn't it hard to adjust the amount of jitter at very low levels for testing? It's not like you can compare device A with device B, since they will differ in a lot of other ways other than jitter. Anyway, I won't discount a possibility, but it's not something I think is probably a big deal, given the levels we're talking about. Then again, most audiophiles don't tend to care about things in the correct order of importance, so latching onto jitter doesn't seem like a surprise, regardless of the actual importance...
Originally Posted by Currawong
dvw: Did you read Dan Lavry's posts? He wrote about the effects specifically. I don't think "jitter has a sound", I think his point was that jitter can degrade the sound, but how much or how noticeably doesn't have simple figure of X picoseconds or X nanoseconds but is complex and depends on many factors.
Specifically regarding USB cables, manufacturers I have spoken to suggested that they need to have the correct characteristic impedance (just as any digital cable should). My feeling at the moment is, having played around with a bunch of combinations of cables, components and other things, is that they should be as short as possible as well, but that could be because the longer cables I've used all passed by other equipment and may have been picking up noise.
I really do wish I could test all of this, as I think it would be good to try and get some useful information that can be helpful to people, so I'll see if that can't be done. Just don't hold your breath, as I've got a bunch of other things I want to do as well.
The most important message from Dan Lavry and Michael Goodman (and what many people have been saying all along) is that jitter matters at the D/A conversion. It doesn't matter what happens elsewhere as long as the jitter at the conversion is low enough. This point seems to be ignored by many.
It's up to the D/A device designer to deal with whatever input signal comes in. For all but the cheapest USB DAC implementations, I really don't see any substantive relationship between the jitter on the USB data transmission that the USB receiver chip sees and any jitter at the output of the DAC chip.
Or is everybody buying expensive USB cables for their $20 USB DAC that uses one of those low-end all-in-one USB receiver/DAC chips (one that actually uses its integrated DAC) that makes no attempt at cleaning anything up, getting better sound quality? And even then, is it an audible concern? Even if it's an audible concern, don't you have bigger issues to worry about with a $20 DAC?
That's even supposing it really matters, that for some reason you're focusing on the cable rather than the USB host and of course the device on the receiving end, that the differences between cheap and expensive cables (which ones?) really amount to something much.
I mean, hopefully people buy expensive DACs before expensive USB cables, and the expensive DACs already took care of the issue. Oh wait, we're trusting audiophile gear to take care of anything properly, aren't we?
Edited by mikeaj - 8/29/12 at 8:37pm