Passive Filter Circuits

Simple RC circuits are shown on the voltage division page.

Vox MRB effect as used in several 1960s solid state amps. Image taken from the MKIII preamp schematic.

Vox MRB

The Vox mid range boost (MRB) effects were found in 1960s solid state amplifiers. They are said to have inspired the creation of the Vox wah pedal. I find these fun to play with, so I do believe that story is probably true. Unlike the wah, this filter is passive and requires you to flip switches. The frequency selection is taken care of by SW1 (3 pos. rotary switch) choosing different capacitor values, while SW2 is a DPDT toggle that switches where the inductors get inserted into the circuit. VR 2 and 3 are TREBLE and BASS controls.