Master clock cables and SQ

The output impedance of the clock generator and the impedance of the cable should be the same as the input impedance of the component the clock is being provided to. If the input impedance of the component the clock is provided to is 75 ohms but one or both of the other impedances is/are 50 ohms distortion of the clock waveform will result.

Regards,
-- Al

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!