Which budget digital cable ?

monoprice

Unless you are absolutely sure that your DAC maintains internal impedance at 75 ohms, get a cable that is 1.5m long. Often the difference in price over 1m is minimal. The extra length makes a huge difference in cleanness and coherence in most setups. This is because the extra half meter delays internal reflections just enough that they don't arrive at the DAC in time to cause jitter.

Gee, that's a very interesting point that I haven't seen stated before, and which does seem very conceivable technically.

If the input impedance of the dac and the impedance of the cable don't match precisely, a portion of the incident signal would be reflected back to the transport. A portion of that reflection would then re-reflect from the transport to the dac. The two-way reflection path, assuming propagation time of roughly 2 nanoseconds per foot, would be 12ns for the 1m cable, and 18ns for the 1.5m cable.

I don't know what the typical risetimes/edge rates are for transport outputs, but it does seem very conceivable that the extra 6ns could move the arrival time of the re-reflection sufficiently away from the middle area of the edge of the original incident waveform so that it would not be responded to by the digital receiver at the dac input.

Thanks for pointing that out!

Regards,
-- Al

Thanks for the suggestions, I will look into the options. The dac for my headphone set up is the Valab NOS dac, a budget priced but musical piece. There is a review here in audiogon. Looking for a digital cable commensurate in price point and performance. The above suggestions are really helpful.

Almarg, I have posted on this simple measure a few times now because its benefits are great compared to the cost involved. Yours is the most useful and enlightened response I have yet read. Thanks in turn for it.

I first heard about the phenomenon in a post here by Empirical Audio's Steve Nugent (audioengr). On his Web site's first page he has a link to a technical paper of his which explains in detail ("Paper on S/PDIF cable length in PSOnline"). I had to try it myself, of course, so I made up two otherwise identical lengths of Apogee Wyde Eye. The listening tests I did with a friend were perfectly conclusive: the longer cable was better (with our gear) by a wide margin.

Tobias & Al,

Thanks for pointing this out. Everyone seems to agree that jitter on digital interfaces are a problem sometimes a badly audible one - several AES papers refer to this. I'll have a look at the paper you mention from Steve. I have always used 2 meter or longer digital interconnect cables (Toslink) but only for convenience. Would it be the same issue for Toslink?

Certainly, most of what I have read stresses the importance of jitter rejection/immunity at the DAC end, presumably becuase changing interconnect cable lengths might work on some equipment but not others...