Words from the Jetter Website:
We have basically left all the goodness of the original intact and have added versatility under the hood (literally)! The New GS3 V2 now has an internal switch that allows for a two distinct Channel 2 voices! There are two switches that are accessible by simply removing the bottom cover. They are clearly marked and there is instructions printed underneath the switch indicating the two modes.
The first mode is the classic GS3 Channel 2 voice which provides a distinct, tight-slightly aggressive-balance with a punchy midrange and clarity. Flip the internal switch and Channel 2 takes on more gain and compression with a smoothness and singing quality that has to be heard to be appreciated! Two distinct Channel 2 options now makes the GS3 one of the most functional and flexible overdrives on the planet. One of the design goals of this update was not only to give you more tonal options but to allow for better matching with a wider range of amplifiers. The new voice can be particularly helpful when using a higher power, cleaner amp or an amp that might be a bit on the bright side when trying to achieve a sweeter, singing lead tone.
This new option for voicing Channel 2 was intentionally placed inside the pedal. It wasn't meant to be an "on-the-fly" choice. Because of the distinct nature of the voice options, it should be readily apparent which one you will want to use given a particular setup. Our main goal was to add function not confusion with too many knobs and switches on the top! As a result, the GS3 retains its tremendous functionality in a clean and logical control layout on the front panel.