A guitar amplifier
I decided some time ago to try taking up electric guitar playing. So, I needed an amplifier and since I am what I am I decided to build one.
Digging in my junk box I found a PA amplifier corpse which was complete except for the tubes. I salvaged this from the local scrap heap. It had holders for 6 small tubes, a pair of EL34 and a GZ34. I knew Marshall uses EL34 in their amplifiers so it felt natural to copy one of them. I experimented a bit and found a load of other schematics on the net and came up with an almost copy of the Marshall 1987 JMP Lead, also known as one of the Plexies. It has a normal and a bright channel and I added a distortion channel to it.
The input section and tone stack.