iCircuit Seems To Work With The Classic Matsumin 12AU7 Overdrive

Man! I so want to build one of these! A tube distortion pedal that runs of 9v. The legendary Matsumin Overdrive, origins are quite sketchy, but commonly reproduced as the DIY "Valvecaster." I guess Matsumin was probably either a Japanese engineer in a small amplifier and and electric guitar factory, or a dedicated hobbyist. The origins are probably the 1960s.

Matsumin Valvecaster starvation mode 9 volt tube overdrive circuit simulated in iCircuit
A software simulation of the Matsumin Valvecaster overdrive pedal.

I know, you're like, "Wait! What?! That's running on 9v!!! A tube circuit?" Well, yes it is 9v, and no, it's not a bug in my iCircuit instance. It's called "starvation mode" amplification. I can't find much about the concept of starvation mode online, other than this circuit in its many, many variations, but my best guess is it's something to do with that thing that happens with some tube amps where, when you turn them off, the volume drops as the power supply filter capacitors discharge, then briefly "bounces" back up a bit before dying completely. Whatever causes it, you can run a 12AU7 or, as in my iCircuit sim, a 12AX7 in starvation mode and generate an apparently sweet overdrive tone. The net keeps going nuts for it as new "pedalheads" discover it with every new generation of guitar nerd.

Previously, iCircuit wouldn't work on this circuit, but recent updates seem to have given us 2 new tubes, the 12AU7 and the higher gain 12AX7. Apparently the 12AU7 is supposedly better for the Matsumin, but the 12AX7 seems to work in simulation. This is cool, because both have the same pinouts, so I could build this and try both tubes in the prototype to see which I prefer. Being a nut for high gain OD, I'm hoping the 12AX7 has a similar tone, but more drive, like it does at proper tube voltages.

A 9v tube sound really appeals, as I try to keep even data signals out of my pedalboard, never mind mains power. Here's the orginal circuit from long ago. My sim and the circuit diagram show two tubes, but there is actually a pair of triodes in each "bottle", making it a single tube circuit.

the original matsumin circuit

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