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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

Project Source on GitHub Project Gallery Return to the LEAP Catalog

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

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - 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
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.