Digital inputs ....is one really better than another?

No, AES/EBU is eliminated from many designs because of the cost savings and panel or board savings, or maybe because it’s a more squirrely interface, or maybe the designer does not know how to implement it.

It is squirrely because the XLR connector is not designed for a good termination to 110 ohm cables and the connector itself is not 110 ohms characteristic impedance.

It’s much easier and less expensive to design and implement a high-performance 75 ohm S/PDIF cable than a high-performance 110 ohm AES/EBU cable.  The cabling or circuit board inside the DAC and Transport are also a consideration.  These are more easily made 75 ohms than 110 ohms.

Steve N.

Empirical Audio

Steve, are you saying that AES/EBU, when done right, is the best connection?

There are positives and negatives with AES/EBU.

Positives:

1) some common-mode noise rejection - this can be accomplished with S/PDIF with a pulse transformer and it’s even better rejection.

2) edge-rates don’t have to be as fast as S/PDIF

Negatives:

1) usually requires a higher voltage than S/PDIF and an additional driver, which adds jitter

2) more difficult to make a good cable because of the connectors and twinaxial construction

3) edges must be consistent, rising and falling and with different timings, a difficult thing to accomplish

The bottom line for me is that if you know how to do S/PDIF correctly, it is the interface that will deliver lower jitter. And here we get to the reason why some manufacturers are preferring AES/UBU:

1) they don't understand how to make a fast S/PDIF interface

2) they don't understand how to match the 75 ohm impedance

I have modded enough different transports to know that these are the facts.

Steve N.

Empirical Audio