Master clock cables and SQ

Right. But assuming you have a choice of outputs on the clock and you get cables with matching impedance, is 50 ohms and better than 75 ohms or vice versa? Thanks. 

If there is a choice between all three impedances (clock generator output impedance, cable impedance, destination component input impedance) being 50 ohms or all three impedances being 75 ohms, I wouldn’t want to speculate as to which would be better. It might be dependent on the design of the specific components, or on the specific cable that is chosen, or it might not make any difference at all.

Good luck. Regards,
-- Al

What @almarg said -- the deciding factor is what the impedance is on the device you are connecting the clock too -- I've never seen a device with clock inputs that has both 75 and 50 -- it's either one or the other and that's what you need to drive.

By the way a poorly performing clock interface can be very odd to track down -- sometimes it just fails to work which is clear but other times problems can manifest as distortion on transients and you can spend hours seeking other causes of the problem in your system before realizing it's just that the clock has gotten mis-synched. That's all to say don't mix 75 and 50 or you can cause yourself a world of pain!

Right. But I will clarify and sharpen the question further:

Two different master clock - clock cable - streamer systems. (Think SOtM master clock and SOtM sms200ultra Neo). All equipment is the same. All cables are from the same manufacturer, the same termination and the same length. All impendances from the in and out connections and cables match. 

The *only* difference is in the first system, all the impendances are 50 ohms. In the second system all the impendances are 75 ohms. 

Question: which system sounds better? The first system (all 50 ohms)? The second system (all 75 ohms)? Is there no difference between the two? Why? 

Why am I asking this question? Because 50 ohm systems are a pain, because there is limited availability of good 50 ohm master clock cables at a reasonable cost. However, good 75 ohm digital cables are plentiful with many choices and price points. Yes. All impendances in the system connections and cable must match. The entire question for me is there any reason to have a 50 ohm system if you can have a 75 ohm system?

I hope that helps. Thanks everyone. 

50 ohm vs 75 ohm is a transmission line technology concept... improperly applied to these very, VERY short lengths of cable.

Which means they generally do not conform (in situ) to the theory that is applied to them.

in such scenarios as this, the transmission is one of a square wave, and thus the leading and lagging edges of the square wave IS the 'information' in the system.

And that... is going to be subjected to more or less distortion, mostly due to cable construction over that of characteristic impedance (in termination), in some important ways.

So a given 50 ohm cable might perform better as digital audio cable vs that of a 75 ohm cable, in a stated 75 ohm termination on both pieces of gear. might, being the operative word.

Eg, our liquid metal digital audio cables have no conformation to any transmission line standard, yet they perform in the top echelon of RCA terminated digital audio cables. Different technology, different result.