[BC] The XLR pinout debate

[Stevan A. White]

Shure, Soundcraft, Mackie, and many others (including me) say pin 1
(shield), pin 2(+) and pin 3(-).  Now if you are wiring a vocal mic for a
male and want more peaks to swing positive than negative, wire it pin 2 (-)
and pin 3(+); or, bass ackwards.  I can't think of any situation that would
be beneficial for except perhaps an AM ham radio setup that is short on
audio processing.  Otherwise, I'd stay "in phase" with the standard set by
the industry, unless, of course, your facility staff marches to the beat of
a different drummer.

I also saw a comment about Leonard Kahn's Symmetra-Peak somewhere along the
way.  It doesn't change polarity as the comment suggested, it made all the
peaks symmetrical.  And it was passive!  Some years ago I had a chance to
talk to Leonard Kahn and ask him about this mystery box that was dunked in
epoxy before it went in the rack mount case.  All I really learned was that
this unit was manufactured in the "old days" when AM transmission systems
were not designed to handle more than 100% modulation.  It took care of
things quite nicely.

I was introduced to the Symmetra-Peak at an FM station I worked at that had
studios co-located with the transmitter.  We had so much RFI that good,
clean production was impossible.  One day we just happened to find one of
Leonard's black boxes in the junk pile and hooked it up to see what would
happen.  Since everything back then had transformer inputs and outputs and
this was a passive device, we figured it had to help and it did!  Even
though the station was a stereo FM the only stereo sources going to the
board were the 2 turntables and one of our 3 reel-to-reel machines.
Everything else, including all our carts machines and all production
material, was mono.

I have an old Symmetra-Peak I found several years ago and will never let it
go.  It proudly lives in my ham station audio chain along with a mic
processor and a couple other items.  It is the "secret" to my nice, smooth,
clean and almost too loud FM and SSB audio.  I believe what it is is an
all-pass filter does that minimizes phase distortion and asymmetry.  Is that
right, Leonard?

Best Regards,
Steve White, W5SAW
SW Commercial Electronics


-----Original Message-----
From: John Buffaloe [mailto:johnbuffaloe at bext.com] 
Sent: Saturday, August 12, 2006 4:12 PM
To: 'Broadcasters' Mailing List'
Subject: [BC] The XLR pinout debate


I'll take pin 2 for $250 Alex.

John A. Buffaloe


-----Original Message----- [mailto:broadcast-bounces at radiolists.net] On
Behalf Of Mark Humphrey

Now, on to a bigger debate:  on an XLR connector, should pin 2 be wired
"hot", or pin 3?  I say 2, but I know some stubborn guys out there that will
go to their grave insisting it's 3....

Mark