pre amp assistance please

Discussion in 'The Projects Forum' started by Neil Groves, Apr 12, 2012.

  1. Neil Groves

    Thread Starter Member

    Sep 14, 2011
    125
    3
    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.
     
  2. #12

    Expert

    Nov 30, 2010
    16,252
    6,749
    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.
     
  3. Neil Groves

    Thread Starter Member

    Sep 14, 2011
    125
    3
    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.
     
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