[Phil Allison[_4_]]

Bob wrote:

Given a XLR audio source, what is the easiest way to test if it's a
balanced and differential signal vs a non differential signal?

Is there a tester for this? A special setting on a mixer to listen to
each of the two differential signals individually? Or do I have to make
my own special XLR adapter to pass through only one of the two
differential signals at a time?


** You could do that, but still not know the answer.

There are several common forms of "balanced" output.

Variously known as "floating", "impedance balanced", "earth cancelling" and full differential - ie with two identical, reverse phase signals.

The "floating transformer" one is easy, there being is no resistive path from pins 2 or 3 to ground and a low resistance ( ie 50 ohms ) from 2 to 3.

The last one will be revealed by using adaptors like you ask, if both signals are there it will also be 6dB stronger than otherwise when in use with a "balanced " input.

The other two are not so easy and will need reference to a schematic or some test equipment.

FYI Hum rejection comes from the *input* being differential and the use of twisted pair cables.


..... Phil