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Project Notes

#097 Volume Control Power Amp

An LM386 fixed-gain audio power amp with volume control.


This variant in the line of LM386-based amplifiers is based on a design in Beginning Analog Electronics through Projects.

It is similar the Little Gem/A386, but with a few differences:

  • The LM386 gain is actually fixed at 200x with 10μF C5, with volume control on the input provided by R1.
  • it adds a small RF-bypass capacitor C2 to prevent RF-breakthough of radio signals
  • the output coupling capacitor is slightly smaller at 10μF
  • additional 100nF low-pass filter on the power supply

How it performs:

  • the input volume control works fine, although it is pretty redundant as it is ding the same job as a guitar’s onboard volume control
  • the RF-bypass capacitor does appear to give a cleaner signal
  • the lack of gain control means the overdrive level is fixed. It’s a pretty nice and warm effect that cuts in with higher input volumes



The Schematic

The Build

Credits and References

About LEAP#97 OpAmpAudio
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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.