AMZ Son of ScreamerBuild the Classic Overdrive Pedal
The AMZ Son of Screamer is somewhat loosely based on the Ibanez TS-9 Tube Screamer design, which has a lot in common with the Boss SD-1. In the revised pedal, I eliminated the switching circuits and the emitter-follower buffers and went with a simpler design. This minimal overdrive adaptation of the vintage TS has been used countless times by pedal manufacturers, and now you can build your own version with the AMZ pc board.
The buffers are really only important for use with a buffered bypass system and do not contribute anything to the sound.
Note: I have seen numerous times on web forums that there are boutique pedals based on the SOS that have impedance problems. The original SOS as presented here does not have a problem with impedance. It is the mods to the original that will cause the problems.
The basic circuit has an input gain stage built around IC1a with clipping diodes that provide the distortion for this pedal. The non-inverting setup contributes to the smooth sound of this design. The first opamps output drives an R/C filter followed by the active tone control stage of IC1b. It is a simple but effective setup.
How does it sound? It is smooth, low noise signal with the signature mid-range distortion sound that cuts through quite well with a live band. It is perfect for hard driving a tube amp. The sound is not "transparent", but then again, that's not its intention.
Another advantage of the DIY-SOS, is that you can add your favorite mods while building the pedal, and make your own personalized boutique creation.
With only 10 resistors, 8 capacitors and a couple of diodes, the SOS is a perfect first distortion project for a beginning builder.