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Length of digital cable?

Picking up where I left off a year ago, somewhere on the net I ran into a recommended length of 18 ft of digital cable between transport and D/A converter. Various lengths were discussed and one source was very confident of the 18 ft length to successfully resolve jitter. And the Beldon 1694A was recommended. For $30+ or whatever I gave it a shot and was surprised by the quality of sound, and I swear on a stack of owners' manuals that this length with this brand of cable resolves jitter. The sound is rock solid gorgeous.

The Beldon lies behind the system mostly in a coil, and I think coils are probably not ideal. I'm wondering if anyone has found a shorter length that works. Al suggested 8", but I was unable to make it work because the components aren't close enough. I know that 1 ft" doesn't work and that 1 meter doesn't work.

Part 2: Does length of ethernet from computer to avr also affect jitter? My sister who is a computer person and not an audio person set up my avr with computer using cat 5. The sound quality is bad. I'd like to get good sound quality with computer as source down the road but need advice on how to get it.
arnettpartners
arnettpartners OP
312 posts
 
Hi Steve, You were around last year when Al and you and others were pounding into my head what a digital signal is. I thought I could do better than the Beldon but thought I had to be on the right track because suddenly the signal sounds right. Will check out your cable although haven't found it on your website yet. I also noted your suggestions for using computer as source that are listed on your website. Lynne
audioengr
3,282 posts
 
The BNC-BNC cable is on the pulldown menu at the top of the Off-Ramp page. It is generally sold as an accessory to the Off-Ramp, but can be purchased alone. You can also email me and I can send you a paypal invoice.

Steve N.
Empirical Audio
ps68
230 posts
 
We found that the shorter the better if the cable is well designed. I use 40cm, it is astoundingly detailed and tonally very accurate..
arnettpartners OP
312 posts
 
Ps, you use 40cm of what cable?
almarg's avatar
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almarg
9,670 posts
 
Hi Lynne,

I agree with Steve's comments about length, and I don't doubt that his cable is an excellent one. As he indicated above and in his Positive Feedback paper, the optimal length is dependent on signal risetimes and falltimes, which will vary from transport to transport and are usually unspecified. But as indicated in his paper, what probably stands the best chance of being optimal in any given setup is a length of around 1.5 meters (about 5 feet), assuming that a very short length is not practicable.

In addition to signal risetimes and falltimes (the amount of time it takes for the signal to change from its low voltage state to its high voltage state, and vice versa), what length is optimal in any given setup can also be affected by the propagation velocity of the particular cable, by the accuracy of the impedances of the cable and the components it is connecting, and by the amount of electrical noise that may be riding on the signal that is provided by the source, or that may occur as a result of ground loop effects or RFI pickup. So it's all somewhat unpredictable.

Regarding your second question, most likely the length of the ethernet cable is unrelated to the poor sound. The timing of D/A conversion in the AVR (which is where jitter matters) and the timing of data transmission via ethernet are inherently unrelated. It's conceivable that the cable type and/or its length could have a slight effect on sonics by affecting the amount of digital noise that could radiate or couple from the cable to circuit points within the AVR, but I'd expect that kind of effect to be subtle at most.

Best,
-- Al
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