LM386 Oscillator Synth

Discussion in 'The Projects Forum' started by kabum, Dec 7, 2009.

  1. kabum

    Thread Starter New Member

    Oct 28, 2009
    I used a 50 Watt 4 ohm speaker embedded in a plastic encasement from Radioshack with two potentiometers and a power switch.


    I put this together pretty quickly based off of the square wave oscillator schematic in the LM386 datasheet. Since I couldn't find a model for a 3-pin potentiometer in PSpice I figured the 5k pot was split that way but I could be wrong (also excluded the power switch). It's a whole lot of fun and gives you some pretty good control over a high bandwidth with lots of weird interesting things happening at certain combinations of the potentiometers. I'd recommend anyone put this together for like $20 from things at Radioshack. Also, I'm sure the circuit could be improved upon somehow or given some other cool features. Just thought I would share this project with you all.


    Last edited: Dec 7, 2009

    Senior Member

    Jul 1, 2008
    If you plan on using this often you may want to stock up on 9V batteries. Any particular reason why the speaker is rated at 50 Watts? BTW, your cat must love you for making this. :rolleyes:
  3. kabum

    Thread Starter New Member

    Oct 28, 2009
    Nah... it's definitely overkill. My friend saw these speakers laying around his frat house and apparently no one was using them so he pirated them for our projects, and this is the first use of them... haha it's a slight shame, they are good speakers, but i think this is a better life :) Plus, being rated at 50W doesn't mean this circuit can drive anywhere near 50W through this speaker in the first place. I suppose I could so some analysis and figure out how much power really goes through that thing... But I'll save it for later....
  4. Audioguru

    New Member

    Dec 20, 2007
    An LM386 amplifier needs the zobel network of a 10 ohms resistor in series with a 0.05uF (or 0.047uf) capacitor from its output to ground as shown on every circuit in its datasheet.
    It also needs a supply bypass capacitor, 10uf to 470uF.

    With a brand new 9V battery its output at clipping with a sinewave input is only 0.3W into 4 ohms. Since it is producing an awful-sounding squarewave then its output is 0.6W.
    Half of its output power makes the harmonics.