I have a computer mic I want to use with a PA amplifier. The mic has a 1/8 stereo plug and the amp has a 1/4" stereo jack. I tried it out using a 1/8" stereo jack to 1/4" stereo plug but there was no sound output from the speakers, probably because there is no DC supply for the mic from the amp. If I use an adapter and provide say, 12v to the mic, will it work? If so, what are the pinouts (shield, sleeve and front pin)?
Are you sure your amp has a mic-input? Sounds like your amp has the usual line input. If so, buy a mic preamp or a small mixer with a mic preamp and connect this to your amp. Your mic is probably dynamic and needs no phantom power.
If the microphone has a 1/8" / 3.5mm TRS plug, then it most likely expects +5V plug-in power via the CreativeLabs-style SoundBlaster system.
Probably the contacts aren't lining up right because its expecting a mono plug not a TRS. You could try holding the plug half way in to line up different contacts to confirm this. I would splice a 1\4 plug onto the mic, finding the right wires to cross. That should work assuming the mic isn't already blown out having been connected to something it was never intended to. I've blown out my share of sound cards and cheap mics that way. If you do go about splicing be aware that those tiny wires from the mic are insulated with plastic AND varnish underneath that. Strip the plastic and burn the varnish with a lighter.
If it does need +5v power according to Obscure, you could use your computer as a mic pre amp and get a '1\8 to RCA cord' plugged into the line out on your sound card and a 'RCA to 1\4 adapter' going to the Amp (finding which of the L\R wires to use). I'd be careful though when adding a computer to an audio chain.
If it doesn't need +5v: 'Mic' to '1\8 female\female adapter' to '1\8 to RCA' to 'RCA to 1\4 adapter'. Again, you just have to find which works; left or right.
Don't be surprised when it sounds like crap\doesn't work\breaks. Get a $20 mic with XLR to 1\4 or your just messing around.
I use my pc microphone in my mixer with 12V phantom and works correctly.. I have a pc micro with stereo 3.5 make. I connect this with 3.5 stereo female to 6.5 stereo male adaptor. Then connect with other adaptor stereo female 6,5 to xlr and then in to my phantom Power adaptor (12V , no 48V) and then in to my mixer. Sorry for my english.