Help with stereo audio mixer

Discussion in 'The Projects Forum' started by jrfhoutx, Dec 18, 2009.

  1. jrfhoutx

    Thread Starter New Member

    Dec 17, 2009
    I've been looking around and am having a bit of trouble finding an appropriate circuit for my purpose. I'm a bit new to this so any help would be greatly appreciated.

    I'll start by explaining the purpose of this as best I can. I want to combine two stereo audio signals (both trs style connections) into one stereo audio signal (again a trs style connection). The two audio sources are an iPod and a PSP. I would like to keep the circuit as simple and small as possible (not due to lack of skill but because of extremely limited space as all this will be combined into the compact space of the PSP).

    I have seen this thread here:

    but I am not quite sure that any of these circuits meet my needs. If one of the circuits does and I have overlooked it please let me know.

    One other question:

    I would like to be able to control the level of each source (ie. if I want to hear more of the iPod and less PSP or vice versa), so if both sources have volume controls wouldn't adding gain/volume controls into the circuit be redundant?
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    all you need is a very simple passive mixing circuit.

    Just use a medium value resistor (eg. 100 Ohms) from each output to the appropriate input, and connect the ground / screen directly through.

    eg. one resistor from Ipod left o/p to Left amp input, one resistor from PSP left o/p to the same amp left input, then the same with two more resistors for the right channel.

    The resistors prevent the amps in the two devices 'fighting' each other and causing damage, while providing a moderate load.

    The input level to the amp will be about half what it would be with a single direct connection, but as you are working from headphone outputs that should not be a problem. You can use either or both devices at the same time.