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Obscura Octave Blend

Based On
Prescription Electronics COB
Effect Type
Octave fuzz
Build Difficulty
Project Summary
Based on the octave section of the fOXX Tone Machine, this circuit adds a clean blend and a knob to change the character of the octave effect.
Obscura Octave Blend printed circuit board

Printed Circuit Board

What's included?
PCB only. Build instructions and parts list can be viewed or downloaded from this page.


In stock

Complete Kit

Not yet available.
Kits are developed based on interest, so if you’d like to see one for this project, let us know.
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Project overview

The Obscura Octave Blend is an adaptation of the Prescription Electronics COB (Clean Octave Blend), an octave fuzz with blendable clean signal.

Prescription Electronics (PEI) was one of the original boutique pedal companies, founded in 1993 by Jack Brossart in Portland, OR. The COB was introduced within a couple of years and was produced up until the company closed its doors in 2014. PEI made a brief comeback in 2019 and reissued most of their lineup, but after Jack’s passing that same summer, they seem to have disappeared for good.

The COB is a very unique effect. The octave section is clearly based on the fOXX Tone Machine with a few value tweaks, but it’s missing both a tone and a gain control. Instead, the Octave knob loads down the octave stage in a way that does not actually add or remove the octave, but changes its character. At some settings it’s much more suitable for blending, and at others it sounds good on its own with no clean signal. There are a few great YouTube demos of the COB if you want to get an idea of how it works and what it’s capable of, but suffice it to say, it’s far from a typical octave fuzz.

The Obscura is a direct clone of the COB except for one addition: a switch that disables the octave, adapted from our Vulcan (fOXX Tone Machine) project. Its behavior is very different in this circuit. Typically you’ll want to leave it in the down (stock) position because the octave is the whole point of the effect. But there are some interesting and unique sounds in the other two modes, especially in combination with the blend control, so we felt like it was a worthwhile addition.