design

Lo-Fi Overdrive Pedal Design

I know I haven’t updated this in a few months. I took a long holiday vacation to Las Vegas, and then things got pretty hectic at work (doing computer-y things). In that time I managed to set time aside to design a new guitar pedal.

This pedal started by attempting to recreate the Human Gear Animato, an exceptionally rare fuzz pedal made popular by the band Muse. I started building the input stages according to this schematic:

animato_schem

This pedal was recently reverse-engineered by Adam Crowell, and his clone sounds identical to the original. The input stages use two sets of Sziklai Pairs which are similar to Darlingtons, but use an NPN and a PNP transistor. I built these input stages using NOS MP37s and MP41s – absolutely ancient germanium transistors with rather low Hfe gain. In Sziklai pairs, however, gain is multiplied together between the NPN and the PNP. This resulted in some really nice overdrive even though the transistors on their own have very low gain.

I wasn’t able to control the overdrive in this set-up, however. I went through several iterations trying to create a circuit that would allow for a gain control, with little luck. I eventually decided to go with a separate clean channel, and use a mix knob to control between them. I really like how this sounds, so I began laying the circuit out.

lofi_od

This circuit gives a nice late 80s, early 90s type of grunge overdrive. Paired with a delay pedal, this is perfect for surf sounds. I’ll get some audio recorded some time soon.

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