The Underminder Sub-Octave Synthesizer from PedalPCB is based on the old Seppuku Sub-Octave Synth. The Seppuku Sub-Octave Synth
The Sub-Octave Synth takes your guitar signal and adds a little fuzz while dropping things down an octave, or two octaves at the flick of a switch. It is actually quite a smooth tracking octave down effect, right up until you toggle the glitch switch which causes things to become a little less controlled as the tracking jumps about.
The filter control lets you dial in the tone from a thick bass tone to a nasty, nasal, treble. The blend control allows you to dial in the mix from a slightly boosted guitar signal to the full blown octave down. Add some reverb or tremolo and you’ll almost forget you’re playing a guitar.
The Underminer was a very straight forward project with a low part count. The only component that may not be the most common – but can still be found pretty easily online is the CD4046BE. The 4046 is used a lot in the Eurorack work in VCOs which might give you an idea of what to expect with the Underminer.
There were a couple of lesser used resistor values in this one so I had to use my resistor value hack.
This build was the first time that I tried Tayda’s printing service and I was pretty happy with the result.
In the near future I may write up a guide on how I put the artwork file together.