Cam

Identifying +/- of balanced audio signal.
« on: January 03, 2017, 12:20:16 PM »
Hi all,

As the subject says - how can I identify the + and - of a single balanced audio signal? Or more accurately, how can I identify them by measuring? (I have no labels or markings, and the signals are originating in a jungle of surface mount components I can barely see!!)

Thanks,

M


JohnRoberts

Re: Identifying +/- of balanced audio signal.
« Reply #1 on: January 03, 2017, 12:31:44 PM »
If the equipment is balanced (differential)  in/balanced (differential) out, it doesn't matter.

You can determine a polarity flip by sending a dry audio feed, and the feed you want to confirm polarity of into two adjacent channels of a mixer, then sum them together in any bus.

If they are same polarity the summed signal will increase 6dB. If reversed polarity they will cancel.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

Cam

Re: Identifying +/- of balanced audio signal.
« Reply #2 on: January 03, 2017, 12:43:37 PM »
Thank you! Simple, I think sometimes my brain just goes to Spain..

 :)

abbey road d enfer

Re: Identifying +/- of balanced audio signal.
« Reply #3 on: January 09, 2017, 12:21:41 PM »
Hi all,

As the subject says - how can I identify the + and - of a single balanced audio signal? Or more accurately, how can I identify them by measuring? (I have no labels or markings, and the signals are originating in a jungle of surface mount components I can barely see!!)

Thanks,

M
You have to determine first against what you want to check the polarity; evaluating polarity involves the existence of a stimulus that can be established as the reference.
If the apparatus is electrical in/electrical out, it's easy to check them with a dual-trace scope; where it is complicated is when the input is not an electrical one, for example a microphone. Then you need an acoustic source, which polarity can be assessed, and that is not easy.
Fortunately, there are some simple tools that allow checking the polarity of systems, even if their input or output is acoustic.
http://www.laaudio.co.uk/product_pc90_1372.aspx
http://www.nti-audio.com/en/solutions/live-sound/pa-rental.aspx
Who's right or wrong is irrelevant. What matters is what's right or wrong.
"The important thing is not to convince, but to give pause for thought." (B. Werber)
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