[Tig] Grouping XLR outputs to a stereo signal

Michael Poimboeuf mkp at poimboeuf.com
Sat Oct 28 01:37:23 BST 2006


Generally Left channels are routed to odd number tracks, and Right
channels are routed to even number tracks. If your mixing table only
outputs Left and Right signals, then you only need to connect channels 1
and 2.

Note that some equipment uses the AES3 digital audio interface - while the
left/odd, even/right rule still applies, AES3 XLRs are generally
configured as AES1/2 and AES3/4 on DTRs with _two_ XLR connectors. Since
your equipment has four connectors, I assume that it's analog.

XLR connectors are generally balanced. The professional audio standard for
XLRs is:
AES14-1992 (r2004): AES standard for professional audio equipment --
Application of connectors, part 1, XLR-type polarity and gender
Which you can download from:
http://www.aes.org/publications/standards/list.cfm

Note that some Telecines and Video decks don't follow the AES14 standard.
Not that they're "wrong" but the standard wasn't written till 1992. While
all XLR connectors should have pin 1 connected directly to chassis ground
and the cable shield at the entry point into the unit, the active signal
pins, 2 and 3, are sometimes reversed. Check your polarity, and make sure
it matches AES14.

If your mixer is unbalanced, the best way to make the connection between
the balanced and unbalanced equipment is to use a _balanced_ cable.
Connect the "hot" (+) wire to the + connection, on the XLR  (see AES14 and
check to see which one of 2 or 3 is hot in your equipment), and connect it
to the unbalanced signal (always the hot) on the unbalanced end (either
the center of an RCA or the tip of a 1/4" TS jack); and connect the "cold"
(-) wire to the "cold" (-) pin on the XLR (see AES14...), AND CONNECT THE
COLD (-) WIRE TO THE GROUND/SHIELD on the unbalanced equipment. This last
bit is in caps because more often than not folks just short the cold pin
on the XLR to ground, which defeats the CMRR feature of the balanced
equipment, which is why more often than not you have 50/60 Hz power line
hum in the equipment afterwards.

If you're connecting balanced TRS outputs to balanced XLR outputs, you can
just plug them in, UNLESS your equipment is wired reverse of AES14 in
which case you either have to flip the hot and cold wires in the cable or
rewire the equipment so it has standard polarity... and if you've read
this far, I'll tell you what AES14 would tell you: pin 2 hot, pin 3 cold.
On balanced TRS connectors the tip is hot, the ring is cold, and the
sleeve is shield/ground/return.

AES14 also tells you how to wire 5 pin XLRs for audio.

-- 
Michael Poimboeuf
Screenwriting-Production
mkp at poimboeuf.com
Consulting Engineer, Digidesign/Avid
mkp at digidesign.com

Andreas Wideroe Andersen wrote:
...
> On the back of the FDL telecines there are 4 XLR
> audio outputs these I have connected to a mixing
> table which outputs a L and R stereo signal.
>
> My question is: Which of the 4 XLR outputs of the
> telecine should I group together to get the most
> correct stereo signal? Should XLR output 1 and 2
> go together on L and 3 and 4 on R or perhaps 1+3 and 2+4?
>
> And are these XLR outputs balanced or non balanced signals?
>
...






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