RunOffGroove 22/7 Build

Here is another 22/7 build. It’s a Big Muff variation. This unique circuit replaces the transistor stages of the classic Big Muff with CMOS inverters. It’s a unique flavor of Muff. CMOS inverters have their own unique flavor of distortion and have been used in many classic pedals like: Craig Anderton’s Tube Sound Fuzz, Way Huge Red Llama, Blackstone Appliances MOSFet Overdrive.

The 22/7 was created by the unstoppable genius over at They have a lot great stompbox designs and great information, be sure to check out their site.

Build your own

I designed the PCB and created a project over at OSH Park. Check out my build Docs to read more about the circuit and learn how to make your own! The PCB is designed with the the pots, switch and LED mounted to the board for ease of assembly.

Build post here for parts and PCB:

Build Process

For this build I used a powder coated enclosure and milled the labels and logo through the powder coating with a desktop mill. This process works for me and I can do everything myself at home with no chemicals and little set up and clean up. I want to give UV printing a try in the future, I’ve seen a lot great results! I’ll be writing a blog post about it in the future.

What’s it sound like?

Sounds a lot like a Big Muff but with its own character. The hex inverters have their own flavor but the strong clipping inherent in the Big Muff architecture dominates the sound giving it the characteristic Big Muff sound. I suspect you hear hex inverters as the last inverter is overdriven by the rest of the circuit. I’d say you get the classic Big Muff clipping sound but you don’t get the over saturated sound you can get with a Big Muff when the input is too hot or the sustain high.

The 22/7 has a switch that changes the range of tone control through three different ranges. This changes the range and sweep of the tone control to match other big muff models. There is a Classic option which is described as an average tone model of classic Big Muff models. A Flat option which creates a flat tone response removing the mid scoop of the classic mode, this is a well known mod. Last is the Scoop mode which creates a deeper mid scoop, I compare this to the sound of the original Way Huge Swollen Pickle.

I like the last mode on its own, but the flat mode sounds better with the band. writing this in 2021 I’m spending all of my time playing at home so all the modes sound great!

This has been my favorite Big Muff of late! It’s got a good sound and the tone control hits a very usable range.





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