As I have a lack of desk channels I regularly use (dreaded) Y leads to plug two (identical) mics into one lead in to the desk, eg, for a mic on each of a guitarist's 4x12s; or for a pair of rack toms. Is this OK, or a terrible thing to do? Sounds OK to me, but I've seen a lot of discussion here about how bad it is to use a Y lead to combine inputs.

It is ok providing both microphones are identical. Electronically there is no danger of damage but you will fall into the usual problems of common gain and EQ setting across both mics.

We do it in the BBC only very occasionally as we are usually blessed with an abundance of desk channels.

Its fine for most things in situations where you have identicalish source material and microphones.

The particular thing too look for is the phase variance. Such as if you were to do this for a top and bottom snare, mids may cancel (or increase) depending on mic position. Toms are ok, as generally most are not hit at the same time. But obviously EQ may require to be different for the different toms.

I've been guilty of y combining a choir where I've got 16 singers, 16 sm58s (was not a situation for distance miking with condensors) but only 8 channels. I just matched up the males, matched up the females...and it was fine.

Obviously does not beat individual channels, but certainly a get out of jail free card when needed.

my2p

Si

I'm not so much of a fan of this technique - while I'm often of the opinion 'phase shift happens, deal with it' this time round, I'd say look at the rane technote 'why not wye' to gain an explanation of why bad things may go wrong. The solution put forward, is to use a few resistors to make a clever combiner, which, for the cost of ten minutes soldering may save you a lot of hassle. I just made a 1/8"stereo to 1/4" mono combiner for laptops using this idea, so you only need use 1 DI box, and it works really well!

Matt

Microphone Isolation Network.

Look at figure 4 on page 2

http://www.shure.com/stellent/groups/publi...pro_sm80_ug.pdf

I made up three of these for use when micing up large drum kits and I am short of channels. They work very well on both dynamic (sm57) and condenser (pg81) mics. Apart from losing a few dB they are completely transparent and I use them regularly. The resistor values do not seem to be too critical as long as they are all the same value (use 270 ohm 1% metal film). I've found them very useful to have in my kit at gigs.

Many thanks - great advice.
Conrad