Long Coaxial audio run?

Is USB effected by all this "Jitter" for example a laptop connected to a USB Dac with like a 15 foot USB Cable etc…?

Is USB effected by all this "Jitter" for example a laptop connected to a USB Dac with like a 15 foot USB Cable etc…?

No it should not be - USB is sending "data" without a timing signal.

Jitter has no affect on data. You can copy a CD a million times - it does not matter.

Jitter occurs when A to D or D to A is occuring. Digital works wonderfully provided timing is VERY accurate (or erros are randomized).

Unfortunately maintaining a precise clock over interfaces is not easy - it is much better to do it all on one chip with crystal clock close to the converter. However, the reason for passing a clock signal along a digital audio chain is to maintain the relative timing of the devices. This is so nothing gets too far ahead or too far behind....if for example the DAC got too far ahead then it would end up having no data and music would stop. If a DAC gets too far behind then all the "bits" need to be temporarily stored somewhere in a buffer. Also if you are watching a DVD with video then you want the sound to stay in sync with the video - so relative timing is often important.

With A USB connection the devices can "handshake" - data is sent or resent upon request so buffers do not overfill and no data is lost and no synchronization is needed.

Your only concern with USB is the jitter quality in the DAC device itself. (Note that USB protocols and communications will have periodic bursts and some data packest will be repetive - so there is still a risk that correlated noise from USB communications (and the draw on the shared power supply) reaches the DAC clock...

Shadorne
Thanks, I figured it was very similar to how an HDMI type device works, almost identical.. Quality will be built depending on the end device. So it makes sense that the quality will be in the USB dac itself doing its job more so than the device storing a file.

This is why I actually put that question out, which is why I can't see any advantage to going the route of a standard Coax digital or Optical cable connection converted at the music serving device in the first place, it seems to me it is much more sensible to put a little more money into a USB DAc these days, Eliminate a 300 dollar Coax digital cable for example and replace with a decent USB then just let a standard computer, or music server device do its job on its end and the DAC take on clocking it and allowing the DAC also the actual responsibility to make it sound good!

Seems to eliminate much of the guesswork in cabling, cost, and basically only one conversion done at the input of the USB Dac once data arrives.. I really don't see putting a cheap USB card on a computer that outputs the Digital coax etc.. at the main device, but of course I can understand people with really good old school DACS wanting to keep their old DAC and this is the only way to convert it price effectively.

Undertow,

Yes and No. In theory Yes. In practice sometimes NO - as the bursts required for USB operation may feedback through the power supply to make the DAC inside the USB device more jittery than an equivalent AES/EBU or Toslink setup. Unfortunately activities close to the DAC itself can affect jitter. It is the same problem in a CD transport...control signals to the servo motor may end up inducing jitter in the DAC clock.

Remember that Toslink and Digital coax have been around longer than USB and therefore DAC designers have had a bit more time to work out all the possible jitter issues and good ways to attenuate them. In that sense a USB communications protocol running off the same power supply might be an added "unknown".

Well then the solution would be a DAC with a USB interface powered off a separate power supply, or maybe a Battery powered supply for the USB charged off the main transformer tap to isolate it with the batteries, and don't batteries supposedly help eliminate jitter on their own anyway or do I have this backwards? Whatever bottom line is investing too heavily into digital at this point is more silly in my opinion cause you can get excellent results today out of many sources without too much money or work compared to 5 or 10 years ago I guess.