Question about boss pedal

[HamiltonPupo]

I was checking some distortion pedals circuits and came across this one: http://www.schematicheaven.com/effec...metal_dist.pdf .
I understood the circuit pretty well except for the tone control (or what i assume is the tone control). Could someone explain to me what happens IC1A? Or point me to some direction so i can understand it?

Thanks

[Ronsonic]

IC1a is just a buffer isolating the tone control circuit from the distortion generating portion of the program. The signal after the clippers is pretty fragile and I'm guessing there'd be too much interaction (changing tone settings would change the distortion characteristics) without the buffer there.

[Mark Hammer]

Yup. Ron nailed it.