Topping D50 and D50s coax input hit or miss

[mansr]

18 minutes ago, Samuel T Cogley said:

I guess what I really need to do is put an oscilloscope on the S/PDIF sources that work (and don't) and see what the differences in levels might be.  But my experience is that at least with these particular DACs, coax S/PDIF compatibility is not universal.  And even if I knew what the voltage window was that worked, I seriously doubt most people know without testing what voltage levels are presented by their S/PDIF sources.

A coax S/PDIF transmitter shall deliver 0.5 V ±20% peak-to-peak into a 75 Ω load. A receiver shall work with input voltages of 0.2–0.6 V.

 

Balanced (AES-3, XLR) sources shall have a peak-to-peak level of 2–7 V into 110 Ω. Receivers shall accept signals of 0.2–7 V. The transceivers are in fact the same as for RS-485.

 

In practice, an AES-3 receiver will accept an S/PDIF signal despite the impedance mismatch. An S/PDIF receiver, on the other hand, may be overwhelmed (or fried) by the higher level of an AES-3 signal.

[mansr]

7 minutes ago, Miska said:

What varies between receivers is how much input jitter they accept to stay locked. I wonder if they use the ESS Sabre built-in receiver (which almost nobody does).

Just how bad do you think the sources are? The limit in the spec is rather generous.

[mansr]

35 minutes ago, Samuel T Cogley said:

Thanks everyone for your responses so far.  I will say the best results I've had so far is from an iFI iLink, so there may indeed be something to the jitter tolerance than @Miska notes above.

Both voltage levels and jitter can be checked with a scope. If you have one, it would be interesting to see the results.

[mansr]

8 minutes ago, Samuel T Cogley said:

I agree.  But appreciate that I would have to measure at least 3 sources that don't work and 3 sources that do to have enough data points to be useful.  I probably won't have the time and access to a scope for at least a couple of weeks.  Stay tuned.

 

EDIT: Don't I need a spectrum analyzer to measure jitter?

There are many jitter metrics, not all of which require a spectrum analyser. Here's a useful article: https://www.sitime.com/api/gated/AN10007-Jitter-and-measurement.pdf