Build a Hungry Rat Distortion Module!

Hosted by Modular for the Masses
Saturday, Sept 10 @ 2pm
Difficulty: Easy

Hungry Rat Distortion Module Build

The HungryRat distortion module features a distortion core inspired by the legendary Proco Rat pedal with some important upgrades and features, allowing it to become a slender but important part of your Eurorack setup. "Hungry" refers to the starve feature of this module. Distortion pedals in particular, may sound better as their weedy little 9V batteries lose charge. This pedal emulates the loss of voltage and current capacity with a whole bipolar power supply circuit carefully designed to mimic what's happening when a dollar-store carbon zinc 9V is giving up its last few electrons.

The starve feature can be voltage controlled, allowing this module to serve as a VCA. It will be non-linear and absolutely packed with distortion, but that's the appeal. The Proco Rat featured a simple low-pass filter as a tone control. The HungryRat improves on that with an active two-channel tone control, which can boost or cut both treble and bass. The tone control was designed with 100K potentiometers in mind, but experimentation has shown a lot of fun can be had by replacing them with 1 megohm resistors.

At the build workshop, we'll have three op amps available to choose from, to select which sound you prefer. I've never noticed much difference with op amps when they're used as intended, but using them in a circuit like this puts them far outside the parameters their engineers intended, so their performance is delightfully different from each other. The dual op amp that most closely matches the specifications of the original Proco Rat amp is the TLC2262, which is fairly expensive as far as amps go. You can also get one of those for an additional $5 charge.

One of the parameters of op amps that's important to their sound is maximum slew rate. When you order your HungryRat, you can select any slew-adjust capacitor you want, from "none please" up to 10nF. Depending on which op amp you settle on, anything from 47pF to 220pF seems about right. Finally, there's LEDs shining light out of the jacks, so when you build it, you get to choose those colors.

This module can use the starved op amp as the active component in the tone control, or use a fully-powered TL072 amp that's already on the board. Three jumpers can be rearranged to select which option you prefer. The "starved voltage" option allows the starve knob and CV to more effectively use this as a dirty VCA, and the "full voltage" option lets the tone control more cleanly adjust the frequencies produced by the distortion core.

This kit includes a PCB/Panel Set with all the board components pre-soldered, only the mechanical parts needs to be assembled.

You will need to purchase the Hungry Rat Kit from Modular for the Masses by sending $60 via paypal by clicking THIS LINK and put Hungry Rat Workshop in the description.

Some kits may be available for purchase on-site, however, you can secure your place in the workshop by pre-ordering your kit.

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