Here are many Audio Effects and Music DIY electronics Articles with Schematics and idea behind the concept. Electronic Music Enthusiasts will find these useful for learning.
Runoffgroove - DIY Articles and Schematics
Some Entertaining Projects are -
Mr. EQ - A simple, yet potent DIY equalizer. Schematic, PCB/perfboard layouts, and photos.
Little Gem - Two 9v battery-powered amps based on the LM386. Schematic and PCB/perfboard layouts.
Eighteen - The Marshall 18W adapted for use as a distortion stompbox. Schematic, PCB/perfboard layouts, and photos.
Tonemender - An ultra-flexible tonestack with clean boost. Schematic, photo, and PCB/perfboard layouts.
Thor - The legendary Marshall 100W Super Lead adapted for use as a distortion stompbox. Schematic and PCB layout.
The Thunderchief project, released in March 2004, was the first runoffgroove.com circuit that was developed using the tubes-to-FETs process. Enlightened and inspired by Doug Hammond's excellent Meteor circuit, we used the same approach in an effort to capture some of the legendary magic of the Marshall Super Lead. The circuit's performance pleased us, but there were issues.
Splitter-Blend - Dual parallel buffered effect loops with blend control. Schematic and perfboard/PCB layouts.
Professor Tweed - The Fender Princeton adapted for use as a distortion stompbox. Schematic, PCB/perfboard layouts, and photos.