Already said.
Blow the button 1 2 and 3 can put squarely at 0 frequencies for which they act or do a bit driver, then you can add gain with the Fuzz knob.
the blow with a blow to the bottom, blow 2-0 Blow3 noon and we have a really good fuzz sound which can become quite aggressive if you push the blow 3 (the treble) and adjusting to the pitch. Button Blow 3 acts subtly alters the acute and the grain (the ratio between odd and even harmonic?) On the second half of the race.
By not pushing too much blow1 (bass) we get some Brian May style sounds with great attack.
I think this is more than an overdrive distortion, it does not fit too heavy metal styles.

UTILIZATION

Two small caveats:

- Power minijack incompatible with PSU type boss (on mine which is 2002)
- The output level is good but not sufficient with micro ultra-powerful double as X2n of DiMarzio, results with this type of microphone sound effect with a less level than without, unsettling for overdrive. Therefore be considered first with singles, doubles or P90 output level reasonable. so it's not really a pedal metallers from beyond the grave.

There should be a programmable model in the manner of Tech21 TRI-AC, it would transform almost preamp.

SOUND QUALITY

A very versatile pedal, almost breathless, manufacturing quality impeccable.

OVERALL OPINION

Unfortunately I do not use it very often. I play most often with headphones on my POD2.