I've been piecing together a Public Address system using off the shelf kits and modules, I've got it working ok with input from a MP3 player, but when I hook up a microphone pre amp I get a low frequency noise out of the speaker. The mic is one from a CB with an in-line switch, the noise is there when the switch is open, i.e when the microphone is off. When the mic is on it works ok.
I was wanting help on how to get rid of this noise, would a filtering cap be needed somewhere?
I'll also be hooking this up in a car, so would a filter cap on the power input be a good idea? and what rating would be best for that?
The pre amp kit **broken link removed**
The Amp module Link
The speaker is a 8 ohm 30 Watt unit, Vcc is currently 12V
I probably should have been more clear, the CB mike is just an attachment to a CB radio, from the look of the PCB inside of it, the switch just interrupts the track leading to the mic (which looks to be an electret)
Thanks for the tip on the volume control, it isn't actually in place yet, I was just guessing as to where to place it, though now I think about it, I did put it in the wrong place