Long Coaxial audio run?

Vvrinc - I spend a LOT of time on the forums educating audiophiles about one of the most pervasive problems with digital audio, and that is Jitter.

Digital audio is comprised of two elements, the data words and the timing of these data words. The two cannot be separated because the D/A conversion of the digital datastream must have both elements. The data must be delivered to the D/A without error and the timing must be recovered or generated so that timing variations are minimized (jitter). This attempts to matche the timing of the original A/D that was performed in the studio with a low-jitter clock. These clocks are critically important for both A/D and D/A.

Here are some white papers I wrote for PFonline that tell more about this:

http://www.positive-feedback.com/Issue22/nugent.htm

http://www.positive-feedback.com/Issue14/spdif.htm

Steve N.
Empirical Audio

So much loss of quality even though it would be a digital signal to the DAC?

The benchmark DAC1 claims to be able to work with a 1000 feet of Cat 5 cable but that is the only one I have seen making such claims. Any digital interface seems to suffer from jitter and longer runs are worse. It can vary from barely audible or subtle to plain bad and each situation is different so it is hard to predict. Good power conditioning seems to help. You need a reclocker or get a DAC that you think can handle it....and test it thoroughly by A/B short versus long runs to satisfy yourself it is doing its job.

Thanks to you both for the most generous advice.

That jitter stuff is, I guess, only OK if you have a career in pole-dancing!

Regards,
8^(

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...