Line-level Muting

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Baylink
Posts: 438
Joined: Wed Dec 15, 2010 3:21 pm

Line-level Muting

Post by Baylink » Fri Jan 28, 2011 8:52 pm

My studio has about 8 wireless mics, of which generally only 1 or 2 are in use at a time. We have no obvious RF issues, but muting's a bit troublesome for our hosts, who often have two hands in front of a camera at the same time, and can't reach the beltpack.

So, what I'd like to do is wire up group muting.

My plan is this:

I'm going to leave all the mic receivers on the inputs they're on now on our Behringer MX9000 (not my fault), and leave them routed to group 1/2 (which is actually a submaster rather than a VCA "group", I'm almost certain).

I'm going to move background music, VT, and everything else to group 3/4.

Then I want to put a mute relay into an insert loop on group 1/2.

The Eurodesk has TRS insert points on all 8 subgroups, which I'm assuming (but will check) are line-level unbalanced.

My plan for the muting relay is to take the send on 1/2 and feed each side into a SPDT relay contact, feeding the NC side back to the return (through a compressor -- I know group compression can be troublesome, but I don't expect problems in my application, where there's nearly never 2 people talking at once), and the NO side to a separate cough/talkback amp feeding speakers at the control position.

A final NO deck on that 3 pole relay will feed 12VDC to a bunch of strategically placed MUTED lamps, probably using red LED truck/trailer stop lights with vinyl letters applied.

The control circuit will be fed by a bunch of different switches, momentary pushbuttons, toggles, and a footswitch for said hosts, plus a switch in the control room, all of which can trigger the mute (we are generally unmuted and live all of 24/7 except during breaks.

Having the *relay*, rather than the switch, control the lights reduces markedly the possibility of a false positive on the lights getting a host in trouble.

My question, though, for the audience here, is this: will the approach I plan to take on the audio side be likely to cause me any audio problems? Clicks, pops, hum from an open insert-return, that sort of thing?

Down the road, I want also to take that control signal and use it to drive a background music fader, fading in over a second, say, after a 2 or 3 second delay, and out immediately over 5-6 seconds, following the mute signal.

We do this part manually now, and it's sloppy, largely because the board is inconveniently located.

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ajstriker
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Re: Line-level Muting

Post by ajstriker » Sat Jan 29, 2011 8:13 am

You may end up with pop/click...maybe not right away, but as the contacts age. It's not a absolute conclusion, but it may happen.

I would be more interested in what happens when the person that's not talking has to cough and hits the button while the other is talking, muting all audio for both. Bam! "Old Japanese Movie Effect"

-A.J.
There's always room for a bigger amplifier!

Baylink
Posts: 438
Joined: Wed Dec 15, 2010 3:21 pm

Re: Line-level Muting

Post by Baylink » Sat Jan 29, 2011 8:37 am

Yeah, right? :-)

In our case, if there's more than one person talking, they're both sitting about 2 feet apart, and they'll all see the Big Rude Muting Lights, so that possible failure mode is unlikely... unless one suddenly gets Tourette's, and the other's muting him (or we are) on purpose-like.

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