XLR A/B?

[m-theory]

I have a buddy who wants to know if it's possible to build an A/B pedal for microphone.  He wants to be able to talk either through the monitors or FOH, separately.  With LEDs. 

I've built lots of guitar A/B pedals, but never XLR.  Not sure what I'd use for a switch, or if there even is such an animal.  Maybe it would require an actual circuit? 

Thoughts? 

[FiveseveN]

You're not going to have much luck with a passive box with footsiwtches. Although there are a couple of ways to approach this.
However, I feel like we're missing something. What you're describing is a strange situation. Isn't the mic plugging into a mixer? Does that not route the signal to PA and monitors (selectively if needed)?

[m-theory]

My assumption is that he wants to run two separate cables from the box, one to a channel to feed FOH and monitors, and the other to feed just monitors. 

[PBE6]

As frustrating as it may sound, I agree with FiveseveN. This is weird. Is he trying to give "silent" direction on stage? Honestly, the best solution would be to have your friend simply turn around and talk to the band. Unless he's trying to make weird ghost noises to creep people out, then by all means.

If your friend hears all the good advice and still wants a mic splitter, a quick Google search yields several designs, most with transformers, some just with resistors. I would pick one and try to add a switch into the schematic, then bring it back to the group to see if there are any obvious issues with phantom power, popping, etc...

But seriously, your friend almost certainly doesn't need this thing.

Good luck!


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[m-theory]

It's not that odd, really.  He's a drummer and wants to be able to call out songs to the band without having that thru FOH, but also wants to be able to interact with the crowd at times. 

I think this could be done with a mic splitter and a simple switch to kill signal from one of the outputs, right? 

[m-theory]

I found one!  Whirlwind makes something called the "SelectorXL."  Can't find anything but a description on their website, so I've asked tech support for details. 

[PRR]

Don't see this as strange or difficult.

I've often done such with finger-switch mikes. Hands-off is a small quirk.

You want two mike mutes. Sometimes we just short a mike, but here that would be bad. We want to open the mike, also short the board input so it won't buzz on open-wire. That needs 2P2T per mike. LED also makes it 3P2T per mike, formerly an odd duck but now real standard in this crowd.

http://oi68.tinypic.com/9tgy6f.jpg

One question is grounding. I have assumed the FoH PA feed "must" ground through to the mike. In a proper balanced line, that may not be essential, but sometimes things are improper. A full solution would switch the grounds, but I bet the on-stage mike will work "OK" even if grounded to FoH; if it is only for calling turns to the band, a bit of buzz won't bother the paying fans much.

Another question: what if both feeds are enabled? The mike feels two loads. This is often insignificant; is widely done for monitor/house splits. And it does not sound like a super-fidelity application. There might be ground interaction with both feeds live. My suggestion is that he always try that mode in sound check to know if it is good to use in performance.

[PBE6]

Ah, there you go. I assume then that your friend wears a headset mic? That makes more sense. I played in a band for 13 years where the drummer was the lead singer, but he used a boom mic a la Levon Helm. He would just turn his head away from the mic and yell the tunes at us. Worked great, but I can see the difficulty in trying to do that with a headset.

This SelectorXL unit looks like a winner, especially if they keep the price under $50. If it's much more, you might actually be able to build it cheaper.

EDIT: Looks like it's $260 at Sweetwater...yikes!!


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[PRR]

> a headset mic?

Ah, after my time.

If the mike needs Phantom Power, then all grounds must be tied together or switched as needed. Both-feeds mode abuses the phantom. However switching Phantom is sure to glitch pretty good.

This *may* be why that pre-made box costs so much: to cover all cases no-complaint.

[m-theory]

Yes, he uses a headset mic...not sure if it's condenser or dynamic, but I'd assume condenser. 

The selector XL definitely isn't cheap, but it looks like it'll do what he's looking for, and he's got the $$. 
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/miclineinst-switchers/selector-xl