The Ruby Amp it's a small instrument amplifier based on the LM386 IC.
Original circuit can be found in the http://www.runoffgroove.com/ruby.html page.
Basically this amplifier is composed by an N-Channel JFET input buffer that adjust the impedance of the instrument pickup. The speaker driving job it's done by the LM386.
You can find an in-depth analysis of this small amplifier in the electrosmash.com page here: https://www.electrosmash.com/ruby-amp-analysis.
The circuit I propose here it's the Ruby Amp with Bassman mod plus a Distortion mod switch.
I've removed the original amplifier circuit of a junked Creative Subwoofer from a Creative SBS 390 2.1 system, and replaced it with the one I've built.
The PCB was design in EagleCAD and printed from a chinese PCB service. The one you find here it's the revised version of the video one. The circuit is the same, I just changed a bit the layout.
I must say this amplifier sounds pretty good to my ears. It's not that loud, but it's enough to play at home.
Notes
- read risk disclaimer
- excuse my bad english