The Crunch Box from MI Audio is a relatively high gain, marshallesque sounding distortion device. With this we said more or less everything about the pedal. Not an overly unique or peculiar effect, but it does very well what it does and thanks to the Presence and Tone pots a wide variety of sounds can be dialed in. For those who look for a “Marshall-in-a-box” type pedal it is definitely worth to try.
The circuit is quite simple: in the first stage of the dual opamp we have a selective amplification of the signal defined by the filter formed by R5 and C5 and the Gain potmeter: frequencies below 723Hz are amplified gradually less and less (does this value ring a bell? Maybe from the Tube Screamer?) In the second stage only very high frequencies are filtered by C8 to lower the noise. The amplified signal then goes to the clipping diodes (two 5mm red LEDs in our case), then to the tone stack and finally to the Volume pot. Very simple isn’t it? Yet with the correct filtering and amplification ratios we get a very good sounding effect.