The GT-500 Effects Pedal from Fulltone is a discrete FET Hi-Gain Distortion and Overdrive Booster in one box. You could think of them as 2 separate pedals, or think of them as stages to be linked together for endless combinations. The Hi-Gain side has Volume, Distortion knobs, Bass, Mid, and Highs minipots. Its Booster Side has Volume, Overdrive knobs, Bass and Highs minipots.
Hard-clipped distortion—the way most guitar pedals achieve distortion—at one point in a circuit can be cool, but stage after stage of FET (GT-500) is very real, very amplike, and has ridiculous amounts of sustain even at low volume. It does the great chunky low-string rhythm stuff and cleans up incredibly well when you turn down the guitar's volume. The Fulltone GT500 contains 9 FETs, 2 Mosfets, and 1 Transistor with no opamps or clipping diodes used.
What's special about the EQ? The Hi-Gain side has a discrete Inductor-Driven Midrange circuit—never been done in a pedal before. 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—this has 100% discrete matched FETs.
This Mid control mixed with a strong Bass and Treble control help give the Fulltone GT-500 the ability to dial in more variations than a simple tone control, which can only roll off the Highs.
The Series Select Switch allows you to choose which pedal comes first (allowing you to instantly change the order of the 2 circuits). For example: A clean boost slamming into the front end a Distortion sounds way different than a Distortion followed by the clean boost, and when the EQs of the respective sides come into play, it's a wide-open canvas. Regardless of which side of the effects pedal is designated as first in line, you can still use each side by itself, completely independent of the other side.