[Scott Dorsey]

In article , 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?

Measure signal with your dmm. Are both legs driven? If both legs are
driven, assume it's really balanced.

If only one leg is driven, it could be impedance balanced, or maybe not.
Measure resistance from the un-driven leg to the ground pin. If it is zero
or infinite, you have an unbalanced source. If it is a couple hundred
ohms, then someone has attempted to make it impedance-balanced. The value
you measure is the effective output impedance of the undriven leg.

Now..
Put a test signal into the input, measure the output with a dmm. Then see
how much shunt resistance to ground you need to add for the signal drop to
half the open-circuit value. This is the effective output impedance of the
driven leg.

If the two impedances match within a percent or two, you have an impedance
balanced output.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."