Hi Guys, well i just got around to finishing my colour organ and all is now fine when i apply a line level signal, i now wish to add a pre amp at the front end so i can select either mic or line to drive the circuit, i don't know much about pre amps in terms of input/output voltages but i am assuming with a mic insert, i am dealing with a few micro volts? i need to raise this to a couple hundred millivolts using an op amp since i have one half of a dual op amp unused on my board, i can't seem to find a circuit online surprisingly, could someone point me in the right direction please?

Neil.

 

While you're assuming a mic insert, you will need to assume exactly which microphone and what loudness it will be hearing. That can make the difference between a single millivolt and 3 to 4 whole volts (p-p).

Humans can enjoy music from maybe 60 db to 120 db. That is a HUGE difference in voltage gain.

 

it needs to pick up music at a comfortable level in the room and generate enough voltage to drive filters made from an op amp I.C

Neil.