Identifying +/- of balanced audio signal.

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Cam

Member
Joined
Mar 24, 2013
Messages
15
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
 
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
 
Cam said:
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
 
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