Two mics in one jack


I'm curious if it's possible, via some sort of of y-adapter or something, to plug two hand mics into one jack on stage. They would obviously both be on one channel on the board. Is it possible?
Where would I get such an adapter? Would Rat Shack have one? And what would you call it?

Thanks a lot.
That's a mess waiting to happen....It's much harder to control two mics from one channel that you'd think. Plus, I doubt the pre-amp is meant to handle that...
I would expect that they would have used an external mixer or some form of a summing amp to combine the signal.

Y-leads can cause problems when they are being used in this manner as signal coming in from one mic can travel into the other mic and vice versa. There will also be some signal cancellation as well

This is why a summing amp or resistor snub circuit is used when converting a true stereo signal into mono one.

Simple experiment. Take 2 CD players and run the outputs into a Y-lead and then into your desk. Now, whilst music is playing, unplug one of the 2 CD outputs. Notice what happens to the sound?
Mayhem--I don't know much about electronics, but what if on every lead in the cable you wired a diode? I don't know exactly where, but if you did that, then it would prevent the electricity from traveling bck up the mic lead....
Audio signals are AC so a diode would not work. Depending on which way you wire in the diode as to whether you would drop the positive or negative deflection of the sine wave.


For even more control

it is very possible. sometimes when doing gigs with a smaller board, channel space becomes a big issue. so i soldered my own adapter to run two rack tom mics into one channel. works like a charm every time!
How did you make the adaptor?

Whilst it might work like a charm, it may still cause damage.

I have/had the schematic for a simple resistor network for summing two signals. I also have the schematics for a summing amplifier as well, which is active and therefore does not cause any signal loss, like the resistor network will.

If anyone wants them, let me know.
i just soldered the leads together (1 to 1, 2 to 2, etc.) and then soldered them to the xlr jack.

i wouldn't mind havin a look at those schematics though
Scooter said:
i just soldered the leads together (1 to 1, 2 to 2, etc.) and then soldered them to the xlr jack.

i wouldn't mind havin a look at those schematics though

Ah! the classic Y-Lead. Has the potential to cause damage to your equimpent and I will have a look for those schemaits for you. The resistor network should fit into the XLR.
I actually saw this in use in a Boston Pops show, all their SM81s were dualed at the sub-snakes.

The preamps can take it as long as the impedance doesn't drop low enough to start "shorting" out.

To directly connect two outputs together into the same input is dangerous, and can damage equipment. For details, check out this tech note from Rane:

If you must do this, use a combiner like the above box or the circuit shown on the page I linked to to do it safely.

Great link!
The circuit shown in the link provided by Andy is the same as the one that I have. The active summing amp one is on the way once I find my note book that has it in there.

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