Congratulations on buying the Dr Freakenstein Chop Fuzz! This is the most extreme distortion effect to emerge from the laboratory of Rainger FX – coupled with modulation and hard squarewave (‘chop’) tremolo, and we hope you have serious fun with it.


Knifeswitch; Power to the unit is turned on by throwing the knife switch manually. (Do this when you’re setting up). In ‘power off’ (up) position no power is drawn from the battery.

ON/OFF; This footswitch puts the Chop Fuzz into the circuit, or bypasses it (with hard-wired true bypass).

OVERTONE; Turning this knob changes the harmonic overtone of the sound. The distortion circuit has a kind of inherent noise gate-type of effect built in to it, which means the unit is totally silent between notes.

VOLUME; This adjusts output volume, while the ‘eye’ meter monitors your input signal.

MOD. ON/OFF; This switches on a modulation control, which has the effect of moving the OVERTONE control backwards and forwards (this knob now controls modulation width).

LFO RATE; This controls the MOD oscillator speed, its frequency shown by the throbbing white meter backlight.

CHOP RATE; This controls the speed of the chop tremolo, shown visually by the red strobing LEDs either side of the meter.

CHOP; On the top end panel, this PCB switch engages the ‘chop’ tremolo. BTW the MOD ON/OFF switch needs to be on (down) for the CHOP switch to work.

HI/LO; On the top end panel, this pushbutton switch changes the effect from a low intensity to a high intensity overtone.


Dr Freakenstein’s assistant is Igor. It’s a pressure-sensitive controller, which, when plugged into the IGOR input on the top end panel, controls either OVERTONE, or the chop effect – depending on how the pedal is configured. Igor is dual sensitivity; use it shiny side up on a hard stage with shoes, or rubber side up if you’re sitting down or barefoot (difference in sensitivities will be less noticeable if you’re using it on a carpet instead of hard floor). Or use it with your hand!


  • The unit works best with your guitar’s volume up full, otherwise the noise gate kicks in too early and compromises the sustain.
  • Plug external 9v PSU’s into the ‘DC in’ socket (centre earth, sleeve +9v)
  • To preserve battery life when not using the effect just throw the knifeswitch off (no need to unplug your ¼” input jack). Then it’s easy to see that you’ve turned the power off.
  • To change the battery, unscrew the three screws on the underside panel.

If you have any comments or questions please do get in touch at www.raingerfx.com , where you can also find out about other Rainger FX products.


Note: This User's Manual is adapted from the official manual created by Rainger FX in PDF format, without modification of the content. We just rewrite the PDF, into responsive mobile friendly pages.So, you can read this document anytime and anywhere.

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