Digital Coax Cable - Does the Length Make a Difference

I have recently heard definite differences between a 1 meter and 2 meter digital S/PDIF.  This includes even a true BNC to BNC cable with proper BNC connection on source and DAC.  Using a Nordost Heimdall 2 cable, there was a loss of high frequency response and detail with the shorter 1 meter cable.  The 2 meter cable solved this problem as well as some other "not quite right" things with the shorter 1 meter cable.

@auxinput  Thanks for the info. 

I was aware of the explanation for S/PDIF.  I’m curious if the same applies to USB and other digital implementations.  I would assume yes.  Jaytor of Kijanki?

I was aware of the explanation for S/PDIF.  I’m curious if the same applies to USB and other digital implementations.  

No, I would not expect the guidelines for optimal S/PDIF cable lengths to apply to USB.  For one thing, modern USB implementations (i.e., those operating at 480 megabits per second and higher) have far faster risetimes and falltimes than S/PDIF (or AES/EBU), which operate at vastly slower bit rates.

FWIW I don't recall ever seeing meaningful information as to what cable lengths for USB tend to be more optimal than others in audio applications, if it makes any difference at all.

Excellent answers by Kijanki and Jaytor to the original question, BTW.

Regards,
-- Al
 

Shorter USB cables will not be a problem. The biggest difference is that the USB clock is not used to generate the DAC sample clock on modern DACs, so any jitter introduced by reflections from the connection will not cause DAC clock jitter. 

That's not to say it will not have any impact since it can contribute additional noise, but it's likely that other noise transmitted through the USB connection will have a larger impact. And a longer USB cable provides more opportunity for noise to be picked up in this connection.