Fork me on GitHub

Project Notes

#104 Ruby Guitar Amp

A version of the runoffgroove Ruby LM386 guitar amp.


The Ruby amp is similar to the LittleGem, however it introduces a JFET buffer on the input and discrete volume and gain controls.

The build here is based on the runoffgroove schematic, but with a few variations:

  • adds a coupling capacitor on the input
  • J201 n-channel JFET instead of the original MPF102



NB: in the schematic below, the FET symbol is not quite correct (shows n-channel MOSFET instead of JFET)

The Schematic

Breadboard Build

Running the amp on a breadboard is possible, but noise and interferance can be a real problem. So performace on a breadboard is not a very good indicator of actual performance if you build the circuit on a PCB.

The Build

Prototype Build

Running on a protoboard. Works really well! I need to find some pots to replace the trimmers then I can mount it properly.

Here’s the layout I used:

The Schematic

The Schematic

The Schematic

Credits and References

About LEAP#104 OpAmpAudio
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, 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.