Test XLR audio source for true differential signal?
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
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