FXBus 1 Module 9 - a Big Muff style clipper 

Copyright 2000 R.G. Keen. All rights reserved.

Module 9 is a Big Muff Style feedback diode clipper - that is, it does distortion by putting diodes around the feedback path of an single transistor rather than a diode. This is very similar in principle to the clipping stage of Ibanez' Tube Screamer series.  For a detailed discussion of the workings of a feedback diode clipper, see "The Technology of the Tube Screamer".

Here's the schematic and layout:


Here's the parts list and what each part does (Note - caps in uF unless noted; pots are audio taper unless noted):

Part Value Notes
R1 8.2K
R2 150K
R3 470K
R4 10K to 15K
R5 100 - 150
D1, D2 See Text Usually 1N914/1N4148 silicon, may sub other types for special clipping needs.
C1 1uF, see text
C2 470pF  
C3 1uF, see text  
C4 1uF, see text  
Q1 2N5088 High gain silicon NPN; 2N5088 recommended, but actual type number doesn't matter much.