Why do digital coax cables matter?

...True, but we are not talking about bit errors here, we are talking about psecs of jitter. The cable matters, as does practically everything else...

Jitter is directly tied to the Eye pattern tests, so the concept is valid for digital audio. The percent jitter is actually calculated off the eye pattern. The jitter in turn can be used to predict BER rate.

Rower30: what you have outlined is my understanding as well, based on Rf transmission theory. Impedance match at the connectors and loss tangent (dissipation factor) in the cable are the two key parameters.....everything else is secondary. That is why cheap CAT5 cable is far superior to most analog audio cable for digital transmission.

Also reclocking the data at the DAC is the key to superior reproduction.
Putting the clock in the data stream was poor engineering from the start. Fortunately, HDMI 1.3+ provides for this and is generally superior to any SPDIF interface, (even with million dollar cables), for this reason. Buy an Oppo BDP-95 and a DAC with an HDMI 1.3 input (Meridian HD621), and you won't have to worry about jitter.

Steve Nugent Wrote:

'Jitter measurements are a rat-hole IMO. Jitter has never been effectively correlated with SQ anyway, and based on my experience, it is very dependent on the spectral signature of the jitter. Single jitter measurements are useless to say the least.'

Bingo - we have a winner.

I have mucked around with all sorts of sources and thats it exactly.

Thanks
Bill

Dcbingaman wrote:

'Fortunately, HDMI 1.3+ provides for this and is generally superior to any SPDIF interface, (even with million dollar cables), for this reason. Buy an Oppo BDP-95 and a DAC with an HDMI 1.3 input (Meridian HD621), and you won't have to worry about jitter.'

You must listen to different HDMI stuff than me. On my NAD M51 SPDF and USB easily bests HDMI. And when fed with an Off-Ramp which has jitter below 10ps you can easily hear the improvement over any other method. HDMI is far from jitter free - not by a long shot.

I hasten to add it probably has nothing to do with the interface per-se but what's feeding it via the interface.

Also anyone one who thinks there is any method available today where you don't have to worry about jitter they are whistling dixie. Even on sources with jitter below 10ps like the Audiophello 2 and Off-Ramp you can easily hear the difference.

I have a Playback Designs DAC that they advertise as jitter immune. Even on that DAC you can hear the difference when fed with a low jitter source like an Off-Ramp - although it is not as great as with other DAC's - but it is still there.

Thanks
Bill

Rower - if you are getting bit errors, the eye pattern is so bad that jitter is the least of your concerns.

"reclocking the data at the DAC is the key to superior reproduction"

You would think so, but unless you can synchronize the source to the DAC using word-clock, it is not the best solution. Very few sources have this capability.

You will achieve much lower jitter making the source jitter low and feeding it to a DAC without internal reclocking. This is because all of the techniques for asynchronous reclocking for jitter reduction in DACs are inferior, both PLL and ASRC.

Steve N.
Empirical Audio