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Harmonic Tremolo / Vibrato

The CHEWER-mini uses an all discrete and optical analogue circuit to create a very musical modulation of phase, tone and pitch which is reminiscent of vintage vibe, rotating speaker and valve amplifier harmonic tremolo type effects.

The FET input amplifier section gives a great feel and response to your input signal, which is then split into two separate paths with opposite phase. These two signal paths are filtered independently to give differing tonal characteristics. They are then mixed back together via an optical component* that is being modulated by an analogue LFO, creating the phase and tonal shifting effect with lovely touch of pitch vibrato. This is all rounded off by a FET output amplifier section and an internal master volume trimmer that can be set to taste.

The single external control sets the rate of modulation, with a chunky knob that can be turned and tweak with your foot whilst playing.

For the most pronounced effect, place after your overdrive and distortion pedals.

But I would also recommend trying before your gain pedals, for a slightly more subtle modulation where the overdrive responds to the tonal shift of the CHEWER-mini.


Speed of modulation.


True-bypass footswitch with ON status indicate by lit white LED.


6.35mm (1/4”) mono jack cable input.


6.35mm (1/4”) mono jack cable output.


2.1mm centre negative 9V DC power supply input.

The current draw of the PUMPER-072 is less than 20mA.

I recommend using a good quality regulated 9V DC power supply.


Internal trimmer (marked “103”) to set the master output level.

Can be adjusted by user to taste.


Internal trimmer that sets the voltage bias of the LFO and optical component.

This has been preset for best modulation response.

I recommend leaving this alone, but adjusting will not damage the circuit.

* The all important optical component within the CHEWER-mini has been very carefully chosen to respond as desired with this circuit whilst also being declared as RoHS compliant.


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