AES48 , is there a test to determine?

I have determined that my DAC and amp do not support the AES48 standard.

If that is the case, you may not be able to run cables long distances and you might run into ground loop issues. But if there's no ground loop (which is entirely possible) than its not so much of a concern. I use Mogami Neglex in my home system. I've tried other cables but really don't hear a difference worth causing my hand to move other than to say this :)  Mogami Neglex cables are not expensive; you might pick up a pair and see what you think. If you don't hear a big difference than I'd say don't worry about it!

It was partially your high opinion of the HPA4 that lead me to try purchase one. Since the HPA4 is AES48 even though it has both balanced and single ended outputs without a switch (please comment Ralph)

Without a look under the hood I suspect that this preamp does not support the standard because it has RCA outputs that seem to be in parallel with the balanced outputs. A DVM would answer the question easily enough. Again, the balanced standard ignores ground- its literally not part of the audio circuit. Here is a nice primer about balanced connections:https://www.ranecommercial.com/kb_article.php?article=2107
As you can see, in a balanced connection the ground is chassis ground, not the audio ground. An RCA needs the sleeve connection to the same as the audio ground, not the chassis (which is why you usually see insulating washers with RCA connectors). Since the sleeve is audio ground and not the chassis, this would mean that the XLR ground (pin 1) is at audio ground. This is why AES48 is usually not supported if you see both types of outputs together. But it is possible to get around this by having additional circuitry driving the RCA output that is in parallel with that driving the XLR outputs. Then AES48 can be supported. That is why I say 'without a look under the hood', and why I've been careful to employ caveats.

Yes.


If you have an amplifier with a single-ended input, use an XLR adapter that connects only to pin2 and pin1 of the XLR output of the preamp. NOTE: pin 3 should **not** be connected for this test. Connect to the amplifier and listen to the result.


If it is free of buzz or hum, the preamp does not support the standard. If it does have hum or buzz, this is because the circuit is incomplete (pin 3 isn't connected).


A balanced source ignores ground and does not reference it- this is why you get the buzz with this hookup. In a balanced system the pin 2 signal is created with respect to pin 3 and vice versa. In the old days (and still today) this was/is done with an output transformer. That is why a lot of pro-audio studio gear has output transformers even though it might be solid state.


A quick and dirty, less accurate means of making this determination is if the output of the preamp has both RCAs and XLRs and there is no switch for going from one connection to the other, it likely doesn't support the standard. But if you have a DVM, you can measure for continuity between the center pin of the RCA and the pins of the XLR. If any have direct continuity and there is no switch as mentioned, then the standard is not supported.