The Hi-Gain side has a discrete Inductor-Driven Midrange circuit....never been done in a pedal before. Yes there's a wah wah inductor inside the pedal that gives the Midrange control its ability to drastically increase or decrease the entire Low Mid, Mid, and Hi-Mid frequencies, to comical proportions. All this is done without any opamps because all of the active 3 Band EQ's I've tried are horrible, killing all harmonics, all excitement, and sounding as sterile as the "EQ" in a Digital Recording Program. Nope, this has 100% discrete matched FET's ;)
This Mid control mixed with a strong Bass and Treble control help give the GT-500 the ability to dial in more variations than a simple tone control, which can only roll off the Highs.
What's the "Series switch" in the middle do? The Series Select Switch allows you to choose which pedal comes first (allowing you to instantly change the order of the 2 circuits)
Booster ------> Distortion
or
Distortion-------> Booster
Hand built in California, Mike and his team test and quality inspect each and every pedal before shipping, so you and I always know we are getting quality.