The last layout for a while, I honesly don't know when the next one will be uploaded, probably in january. There is three eye surgeries on the horizon...
Anyway, I had athe change to trace an old EHX Muff Fuzz of the op amp variety a few weeks ago. As you know, EHX used parts whatever they had on hand in the 70s so there is lots of different schematics online so I have included several options for some of the values.
My unit had a 1458 op amp, silicon diodes, 47nF for C1 and 100k for R7.
Pretty much a stock Rat with two additional switches. The clipping switch selects between the stock silicons and a assymetric MOSFET/Shottky pair. A Earlier units is supposed to have a 1N270 germanium diode in place of the Shottky The Fat switch toggles between stock mode and Fat mode by adding a 6,8uF cap at one of the RC filters and a cap to ground at the gate of the output buffer.
Here is an old forgotten old cat...
It is basically a Controfuzz followed by three seperate channels for the Treble, Bass and Mid controls. The fuzz can be bypassed so it can serve as an EQ pedal only as well.
Some improvements had to be done to make it more practical.
1. An onboard voltage inverter is added for the required bipolar power supply.
2. Bypass switching.
3. A Master volume control at the output.
4. The ancient 14 pin uA748 single op amps is replaced with dual channel op amps. 1458 op amps has the closest spec to the original but it is worth experimenting with higher fidelity op amps for the EQ section and the summing amp (IC2 and IC3).
