PCB internal microphone to line level?

[RichO]

Hi, I don't know if this is the right place to ask this question or not but I'll try...

I play in a band and I would like to connect a sound activated strobe light controller to a direct line out of my mixer for the kick drum, so the strobe triggers when the kick drum is played. The strobe controller I would like to use does not have an audio input but rather an internal microphone on the PC board.

My question is, can one of these miniature PCB mics be removed from the board and replaced with a line level input simply by using an in-line resistor to reduce the signal or is something like this much more involved?

I realize that there are strobe controllers that have an audio input but they have many more features than I'll ever use, are much more expensive, and are too big in size to fit into my rack case.

If anyone can point me in the right direction it would be greatly appreciated.

Thanks

 

[Buriedcode]

Hi Rich0,

Good to see another musician in here

If I've understood you right, you've got: bass drum -> mic -> mixer -> strobe.

hmm, why the mixer? Unless this isn't for live, but a pre-recorded song/tune.
And also, generally a mixer has multiple inputs, mixes them, and sends the conbiantion out, so maybe other instruments would trigger the strobe (like a dirty guitar riff in drop C). Anyway, assuming you've just got the kick drum coming out of your mixer, linelevel, I would suggest a simple potentiometer, acting as a voltage divider. One lug to the mixer signal, the other to ground, and the wiper straight into the strobe trigger. That way you can fiddle with the pot until you are satisfied that the strobe triggers nicely on the 'kick'. It may work fine if you just connect it up directly. Line-level is quite a bit more than mic level, but you're not listening to it, so any clipping of the input shouldn't really be a problem, it'll just trigger the strobe on very quiet sounds, possibly making it too sensitive.

If however, you've got loads of instruments coming out of your mixer, and you still want just the kick drum to trigger the strobe, then you would need a low pass filter, to get rid of all the instruments above.

Depending on how well versed you are with electronics, a good way to control the level at which the strobe triggers, is to use a comparator. This will produce a single pulse whenever your input (from your mixer) goes above a certain level, which you vary, and its alot neater than a voltage divider.

So, just to cut to the chase. Yes, I would say removing the mic from the PCB and replacing it with something designed for line level should work. Some PCB mic's are powered on the same connector as the signal, so, first thing you'll need to connect to the pad where the MIC was (signal) is a capacitor, say, 10uf. That'll block any DC from the PCB going into any circuit you are planning to use. Then the rest is up to you, just experiment, I don't think you can blow the strobe trigger, and theres no point in building a nice neat comparator circuit if a potentiometer (as a voltage divider) works fine.

Sorry for the lost reply/giberish, but I don't like being vague about things. If I've completely missed to point of what you're asking, sorry, its late

Good luck,

Buried(in)Code

 

[RichO]

Thanks for the reply. My mixer has a direct out for each channel so I can send only the kick drum channel to the strobe controller. I will give your suggestion a shot and see what happens. I would imagine that I could also use the potentiometer to find the optimum resistance and then replace it with a resistor of that value as the kick drum setting will never change (it's electronic).

Thanks again. I will let you know if it works.

 

[Buriedcode]

Exactly, thats generally what I use pots for, when tuning stuff up to spec, measure the two resistances (or just measure one, and subtract it from the total value of the pot). You will still need two resistors, as a divider, but their combined value probably isn't that important as long as the ratio of their values is virtually the same as in the pot. If you've got issues, I'll draw up a quick schem of a comparator, its probably overkill, and I'm sure the pot will do that job well.

BuriedCode