how to replace the 50K volume pot on my speakers with a dac

Discussion in 'General Electronics Chat' started by amateur_24, Apr 20, 2014.

  1. amateur_24

    Thread Starter New Member

    Oct 28, 2010
    Hi Guys,
    I have logitech z50 5.1 speaker set I want to mod so t I can digitally control the volume using a remote. I have all the circuity working except when I connected up to the volume control pod in place of the pot, the output of poor opamp gets pulled up high. So No matter what voltage I set the dac at I get 5v (full deflection).

    At the moment I have an arudino chip driving the dac via some rotary encoders. The output of the dac is buffered using an opamp configured as voltage follower. I wasn't too sure how much power my set uses. AFAIK the cals aren't straight forward since the impedance of the speakers changes with frequency. Therefore buffered it just in case I kill my dac. This new digital circuit is fed from a seperate power source with a common gnd since I didn't know how much power was available.

    The output of the opamp is then fed to where the wiper would of been connected. I say would of because I've desolder the pot. It works fine until I turn the speakers themselves on. The wiper contact all of a sudden has 5v on it. I'm assuming there is a resistor that acting as a pull up somewhere

    Is there a way I can fix this or is what I done stupid and will never work?
  2. crutschow


    Mar 14, 2008
    Need a schematic of your circuit. A pot normally controls the AC sound signal and has no DC so don't understand how you are trying to control the volume with a DC voltage. :confused:
  3. BillB3857

    Senior Member

    Feb 28, 2009