Adventures with Clock Cables

@052rc -  I'm not quite sure what you're getting at, as ALL my digital cables are wire, and they seem to send 0's and 1's quite effectively. Including my USB cable. So I don't see why audiophile1 agrees with you. I do know they have a send/receive function in the associated equipment, so maybe that's what you're meaning?

And, speaking of 75Ω digi cables, I've now measured, across all possible points, about 8 digi coax cables, and NONE of them measure 75Ω, across any two points. They just measure like any other 'normal' phono cable. So where does the 75Ω label come from, and why don't they measure 75Ω if there's no 75Ω measurement anywhere?  I've tried shorting + & - at one end, and measure across the other end, but no 75Ω result! I've also measured two 110Ω AES/EBU cables, and I can't get a 110Ω reading from anywhere. My Fluke meter is working perfectly btw, before someone blames that.

I, and several 'Audiophile' friends who own the other cables would be very interested to hear any explanation, as the 75Ω naming makes no sense to us.

It’s the analog signal, in case of copper digital cables, that carries 1s and 0s in form of electrical pulses - basically voltage fluctuations. Variables - type of material, quality of conductor and connectors. 
With optical toslink cables it’s the light pulses. 
 

No need to start a discussion on whether cables make a difference or not. Search the forums and read up on opinions from both camps. There’s no reason to start this here. It’s been covered ad nauseam. 

Thanks for sharing you experience. 

It is amazing. The pursuit is so full of non-intuitive realities. That analog cables matter, digital cables matter... power cables matter. I think there was a saying from the 70's that sticks no mater what... everything matters. 

@daveteauk 

ChatGPT for the answer

Great question. The “75 ohms” rating of a BNC digital audio (or video) cable refers to the cable’s characteristic impedance, not its DC electrical resistance.

Here’s what that means:

• Characteristic Impedance (75 Ω):
  This is a property of the cable as a transmission line, determined by the ratio of its inductance and capacitance per unit length (geometry + dielectric material). It describes how signals “see” the cable when traveling at high frequencies (like digital audio or clock signals).
• Why It Matters for Clock Signals:
  A digital word clock is a high-frequency square wave (essentially RF-like in behavior). To keep the edges clean and avoid reflections, the cable’s impedance must match the source and load. In audio/video and word clock systems, that standard impedance is 75 Ω.
• If Mismatched:
  If you used a 50 Ω or random coax instead of 75 Ω, the mismatch would cause signal reflections along the cable. That can smear clock edges, increase jitter, and degrade timing accuracy—something you don’t want in a high-end digital audio system.
• DC Resistance vs. Characteristic Impedance:
  If you measured the cable with a multimeter, you might see less than 1 Ω end-to-end. That’s just copper resistance. The 75 Ω rating is not a resistance you can measure with a multimeter; it only appears when the cable is carrying high-frequency signals.

So, in short: the 75 ohms rating ensures proper transmission of fast clock edges with minimal distortion and reflection.

@jfrmusic,

Thanks, it is good to have some concensus that you also find that the higher ranges of Shunyata clock cables are not automatically superior, when noise filters are employed which is not always benefits for some systems, i guess.

How do you connect the N20 to your MSB, did you also try the Shunyata AES or spdif cable between the units or via MSB optical?

Thanks