From Darkglass:
Designed to be the perfect complement to our distortion circuits, the flexibility and portability of the Harmonic Booster is also the perfect one-stop solution for gigging musicians in search of a precise and harmonically rich clean preamplifier.
Boost: Flat -20dB to +20dB cut or boost
Character: Allows blending in the perfect amount of the tone-shaping circuitry. It can be set counter-clockwise for a flatter frequency response
Mid gain: +-20dB @ the frequency selected by “Mid Frequency”
Mid Frequency: Mid frequency from 250Hz to 2.5kHz
Bass: +-20dB @ 80 Hz
Treble: +-20dB @ 5 kHz
DIMENSIONS: 75x111x43 mm (2.95×4.37×1.77 in)