MalacandraBoost / Overdrive

From the vendor

A flexible drive pedal that can go from clean volume boost to smooth overdrive. Includes a 2-band tone stack for treble & bass.

The Malacandra Boost / Overdrive is a recreation of the Xotic AC Booster and RC Booster, two nearly identical pedals that feature a two-band EQ for independent control of bass & treble frequencies. The result is a flexible tone machine that lets you go from a clean volume boost to a thick overdrive.

Looking at the schematic for the AC & RC Booster circuits, it’s very similar to a Tube Screamer, starting with an input buffer and an op-amp feedback diode clipping stage. The two major topological difference are that the AC/RC circuit uses an inverting op-amp stage for clipping (the TS is non-inverting), and the Tube Screamer tone control has been replaced by a Baxandall stage with bass and treble.

The BB Preamp (also available from Aion FX, called the Perelandra) is a similar circuit. The main difference is that it retains the Tube Screamer’s tone control section in between the clipping section and the Baxandall tone stack, hard-wired at the 9:00 position.

Version 2 of the Malacandra has been updated slightly based on direct traces of the current-production AC Booster and RC Booster as well as the Bass RC Booster. With the Malacandra PCB, you can build any of the three circuits by changing a few parts. Instructions are provided for each variant in the documentation.

Note: This project uses a type of capacitor that has been temporarily discontinued by WIMA. Please see our news article about the issue and the substitution spreadsheet for project-specific recommendations. We are stocking a limited supply in the mean time. The build document has not yet been updated to reflect this.