The Mew Drive uses cascaded jfet mu amps to give a totally different sound to the screamer pedals, and all the variants (there are many).
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First some background on how i came to do this pedal.
I am in the middle of making a valve mic preamp and in the valve section i use two valves in the main gain stage and a fixed 18dB gain SRPP (or mu amp) in the second gain stage.

My captive audio engineer alerted me to how nice the mu amp sounds when pushed very hard (so much so that I’ve had to add a pad to the output of the valve preamp section, but that’s another story).
It is impractical to build a two valve pedal, so i thought, a jfet operates in a similar way to a valve, i could use those in the mu amp configuration, so that’s what i did.
There is more than enough gain from the two mu amp stages, and while being very smooth & creamy, i wanted a little more bite as you wound the gain up, to make this an even more versatile pedal. I tried several approaches, but i ended up with a level dependent circuit to add some nastiness at higher gain settings.
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PURR controls the gain in the first stage, TREBLE, MID and BASS are the classic 3 knob tonestack found in almost every amp under the sun, VOLUME adjusts the overall volume out of the pedal