I have owned BIG MUFF DELUX pedal for a while and it worked great, but a week ago I decided to try an EHX Performance Series, Single Output expression pedal. When I plugged it in the EXP port and moved it up and down the MIDS failed and never recovered. I assume that the pedal just mechanically controls impedance of a potentiometer in the feedback of an amp when it is plugged in the MUFF. Any ideas why this happened and which part need to be replaced? It looks like the EXP pedal works with U9 op amp, U10 amp and, possibly DD9 (a diode?) is involved too. What part # are DD9 and U10? Any help to fix my MUFF would be appreciated.