Audio Sum 10 inputs

Discussion in 'The Projects Forum' started by DanRilley, Mar 27, 2008.

  1. DanRilley

    Thread Starter Senior Member

    Jan 13, 2008
    Hi I am trying to mix together 10 audio signals, each having their own attenuator control. I found this schematic:


    For the attenuator can I replace the 10K resistors with 10K pots? and that be that. Also what would have to change considering that I would have 10 inputs rather than 3?

  2. techroomt

    Senior Member

    May 19, 2004
    you can replace the scaling resistors with pots, the non-wire wound type being better suited for audio. this way each input signal can be weighted or scaled. the only problem i see with 10 inputs is that the summed output voltage (Vout = -Rf(V1/R1 + V2/R2 + V3/R3 +...) may exceed the max output of your 741. you may want to go with 20k's. much depends on your input signal levels.
  3. Audioguru

    New Member

    Dec 20, 2007
    Connect the pots backwards and with resistors in series with the inputs. Then adjusting one pot won't affect the levels on the other inputs.
  4. DanRilley

    Thread Starter Senior Member

    Jan 13, 2008
    Thanks for the suggestions. I figured as long as all of the inputs are attenuated correctly the user can make sure the 714 doesn't get too much voltage by keeping everything low. I'll try these out and see what I get.