KCØPET Pages
A Utility Audio Amp
The goal was a simple audio amp that I can use for testing, AF tracing and just general use. I chose an LM386 chip because I have a number of them in my junk box and all of the other parts for that matter. The box is an old 3 1/2" floppy disk case. The speaker is a junk box variety 8 ohm speaker.
The circuit is based on a typical application for the LM386 (i.e. National Semiconductor ) with a few additions:
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10K Gain pot to make the amp flexible for low or high level inputs. The LM386 allows variable gain from 20 to 200.
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Input capacitors to filter any RFI (.01 and .001 microfarads).
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An input decoupling capacitor to keep out any DC bias from test circuits (1 microfarad).
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Power supply filter capacitors (220 and 0.1 micorfarads). This was a lesson learned for me. I left these off the first time and all I had was a low frequency audio oscillator.
Here is the inside. I am coming to love manhattan style building:
