110 ohm Digital cable with 75 ohm input and output


My transport has a 75 ohm digital out (RCA only). My DAC has a 75 ohm digital in (RCA and BNC). Someone told me to try a cable that's a 110 ohm digital cable but is only wired with RCA's.

So it sounds ok- what are the pitfalls of running a cable with the incorrect characteristic impedance? Or is the cable truly a 110 ohm cable only when it's wired in a true balanced mode, which this is not?

I'm confused
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Using a 110 ohm balanced cable in an unbalanced manner will change its characteristic impedance in some arbitrary manner, but it is safe to assume that in most cases it is unlikely to change it to 75 ohms. The resulting impedance mismatches between the cable and the two components it is connecting will, to some degree, degrade the waveform quality of the signal as received by the DAC.

Depending on many variables, most of them unspecified and essentially unpredictable, that may or may not result in some increase in jitter at the point of D/A conversion. Although in principle jitter is always undesirable, depending on its frequency components and other characteristics, and on the overall sonics of the system and the recordings, and on listener preferences, such an increase might under some circumstances be subjectively preferable. For example, as stated in this paper:
Another interesting thing about audibility of jitter is it's ability to mask other sibilance in a system. Sometimes, when the jitter is reduced in a system, other component sibilance is now obvious and even more objectionable than the original jitter was. Removing the jitter is the right thing to do however, and then replace the objectionable component. The end result will be much more enjoyable.

Jitter can even be euphonic in nature if it has the right frequency content. Some audiophiles like the effect of even-order harmonics in tubes, and like tubes, jitter distortion can in some systems "smooth" vocals. Again, the right thing to do is reduce the jitter and replace the objectionable components. It is fairly easy to become convinced that reducing jitter is not necessarily a positive step, however this is definitely going down the garden path and will ultimately limit your pursuit of audio nirvana.

Sibilance in a system caused by preamp, amps and other components and cables can also be so high that changes in jitter are not very audible. This is why there is such contention on the web forums about jitter and its importance.
Consistent with that, IMO introducing a known and predictable degradation of the quality of a signal is not the way to build a system, regardless of how good the results may initially seem to be. One wouldn't (I hope) knowingly buy a digital component designed by someone who allowed its output or input impedance to depend on the value of whatever resistor he happened to randomly pick from a cookie jar of assorted resistors. So why design a system that way?

Regards,
-- Al
Al- thanks for the considered response. Yeah, running a 110 ohm cable between two 75 ohm terminations sounds goofy to me too. But I'm listening to it now, and it sounds quite good.

I don't understand why anyone would purposely design a cable that uses three conductors, is intended for a balanced 110 ohm characteristic, and wire it unbalanced using RCAs.
I don't understand why anyone would purposely design a cable that uses three conductors, is intended for a balanced 110 ohm characteristic, and wire it unbalanced using RCAs.
If a manufacturer did that, a non-cynical guess would be that perhaps in the particular case the cable does have a 75 ohm characteristic impedance when connected unbalanced. Although that would surprise me.

A more cynical guess would be that perhaps the motivation was to make the cable sound as different as possible from competitive 75 ohm cables, in as many systems as possible.

Or perhaps it was just the result of practical considerations involving not wanting to do additional design and development work, or having already designed a 75 ohm cable which proved to be unsatisfactory for some reason, or cost or availability of whatever wire and other materials the designer preferred, or wanting to use wire he already had in house, or tooling considerations, etc.

Lots of possibilities.

Best regards,
-- Al
"Yeah, running a 110 ohm cable between two 75 ohm terminations sounds goofy to me too. But I'm listening to it now, and it sounds quite good. "

You're assuming the 110 ohm cable sounds good because of the higher impedance. That may, or may not be the case. There could be something else in the cables design that accounts for the better SQ. If you can, try some different cables and compare results.
I never said better SQ-

The other digital cables I have in house are Belden 1694A and Black Cat

The Belden and Black Cat do not sound identical. Black Cat is the smoothest, the Belden the most dynamic and this 110 ohm cable? Somewhere between the two
Change better to different. Its still pretty much the same thing.