[BC] XLR Connector wiring and phase...

[Burt I. Weiner]

If you were the only one to ever use that mic and only in a monaural 
situation, not summed with other mics from other sources, then it 
would probably not matter.  When you start to mix (no pun intended - 
really) mics and polarity you will run into a real mess due to mics 
being out of phase.

In years past, before stereo, mics were wired to their connectors to 
produce a positive going Voltage on the positive lead and pin with a 
positive pressure on the front of the transducer.  This was 
particularly important in early AM broadcasting in order to help 
control negative peaks.

If you have a plant that has mics wired with Pin 3 hot and you 
purchase a mic with a pre-wired connector you may be in for a most 
unpleasant experience.  Listen to your final product with left and 
right summed together in mono.  In the last thirty or more years I 
have yet to see a professional mic wired with anything other than Pin 
2 as the positive pin.

Burt


At 10:00 PM 8/12/2006, you wrote:
>From: Cowboy <curt at spam-o-matic.net>
>Subject: Re: [BC] The XLR pinout debate
>To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
>Message-ID: <200608121915.05493.curt at spam-o-matic.net>
>Content-Type: text/plain;  charset="iso-8859-1"
>
>On Saturday 12 August 2006 06:23 pm, Peter Smerdon wrote:
>
> > I'm recalling that before the standard, pin 2 hot was common in UK and
> > Europe, and pin 3 hot in US and Japan.
> > Australia was importing pro audio gear in about equal measure from both
> > camps, so it was a right royal mess down here.
>
>  Though it should not have been so.
>
>  The equipment doesn't really care which is + and which is - since both
>  are carrying an AC signal.
>  An amplifier will amp an AC signal regardless !
>  The only time it would matter, would be if different wiring were on the same
>  cable, or in the case of some polarity dependant device, like the mod input
>  on an AM transmitter.
>  At no other time would it make a hill of beans, until people start thinking
>  it does, and "fix" something that isn't broke !
>
>  I know of no manufacturer that ever sold any broadcast grade gear that
>  reversed the polarity between input and output, except the boxes
>  very deliberately designed to do so, like a symetripeak <sp>.
>
>  Oh, sure, we all know ( or we all should know ) that positive 
> pressure on the
>  microphone diaphragm is supposed to produce positive going voltage at the
>  output pin labled + but how do we know what the polarity was on the
>  record ( that's CD for you kids ) when it was recorded ?
>
>--
>Cowboy

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at earthlink.net
K6OQK