For about three years now, I’ve been teaching myself guitar electronics (which I’ve written about before), and stompbox effects in particular. As a software and data kind of guy, it’s a nice to have a hobby that’s physical — but still technical — and also useful to my band as we explore new soundscapes. After building a few DIY all-in-one kits, I graduated to sourcing my own parts, and more recently to designing my own circuits!
In this post, I’ll talk about the first effect I developed as part of this journey: The JANUS Overdrive. It’s essentially a mash-up of several classic “dirt box” pedals with a switch to toggle between tones based on different clipping diodes (but more on that later). Here is a demo video of the circuit in action:
A Little History…
The JANUS is based on three classic distortions that evolved over the 1970s. The first was the Blue Clipper (1972?), supposedly one of the first op-amp-based overdrives, created by a boutique guitar/effects maker named Dan Armstrong who left amplifier company Ampeg to strike out on his own. According to legend, someone from MXR picked up one of Dan’s units at a convention and their engineers modified it to make the MXR Distortion+ (1973). This was further adapted for the DOD Overdrive 250 (1976), and cloned by numerous other manufacturers over the years at well.
It has been well-known for a long time that the MXR Distortion+ and DOD 250 are the same circuit with slightly different components. In fact, most of the DIY projects you can download or buy online to clone these pedals use the exact same circuit board for both! After researching the schematics online, I identified the ways in which the Blue Clipper was a “special case” of the MXR/DOD circuit, with a few components tweaked or removed, and was able to compile a “diff” of the three units to explore further.