Lamb Chop Fx loop mod

[matt73caster]

Hi,

I am thinking of modifying a Lamb Chop (Way Huge Pork Loin) to add to the circuit a FX Loop activable via a footswitch.
The idea behind this mod is to mimic the behavior of the Way Huge Pork and Pickle = by pressing the footswitch, instead of blending the "clean" signal with the internal overdrive, the clean signal would be blended with any external pedal connected to the FX loop. It could be a fuzz (a Russian muff like in the Pork and Pickle), a distortion ( I would like to test it with a RAT !), or any other type of pedals (octaver for instance !).

I believe that the following modifications would do it, but I would welcome any advise, return of experience on the matter !
Thanks in advance.

 

[matt73caster]

I am wondering if I should not put a 1uF cap between the 3pdt connection 1 and the send output since the input signal should still be biased after the input buffer ?

 

[Feral Feline]

I am wondering if I should not put a 1uF cap between the 3pdt connection 1 and the send output since the input signal should still be biased after the input buffer ?

How's this project going?


Note the DRIVEMIX is connected not only to VREF, but also to the CLEAN pot's lug1. Might create some problems if you're hooking into/out-of the circuit at C18.



I'm no circuit wizard, but here's how I would attempt to go after this — starting from the top...


I'd remove C29 (and R31) from the PCB, they're both going to go on the switch. The INPUT OF C29, the side towards Q1, is going to have a wire from it to lug2 of the 4PDT... lug1 of the 4PDT gets C29 and R31. The 4PDT's Lug3 goes to the SEND jack.

At the other end, I'd wire up/use a TWO-KNOB JOBBIE (you can wire it manually or order a POT-Swapper PCB from GUITARPCB).
I don't know about the new GPCB 2Knob-Jobs, they may have changed, but I used one of the older 2knob-job PCB to mount a 4PDT which required notching the PCB slightly:

I only dug into the ground-plane a little; some nail-polish to seal the deal and avoid possible shorts when soldering in the first pole.

Of course, IF the new 2KNOBJOBs aren't up to the job (the new ones have oval lug-holes), because the routing might be different, you can always wire the switch directly.

Offboard wire the DRIVEMIX to the switch — swap between it and another pot/trimmer that ties the RETURN-JACK back into the rest of the circuit via C24. The RETURN-jack now has its own pot not tied to VRef at all, and the DIRT side of the Lamb Chop is fully isolated from the CLEAN side when the loop is engaged.

Might be worth putting a PDR where the old R31 was, in case the switch is popping.