Like the GR-300, there are three versions of the G-303 and G-808 guitars, distinguished by changes to the PC board.I was contacted by a G-303 player in the States and a G-808 player in Norway both using the first run, early "prerelease" version of the guitar electronics.When switching from the 80 ohm (narrow) to 900 ohm (wide) pickup, there is a 10:1 increase in impedance, likewise, it is necessary to change the negative feedback loop resistor by a similar ratio, from 330K to 33K, and from 1 M to 100K.Mark also mentions that the pick guard must be slightly enlarged to accommodate the wider pickup, but only on the G-202 and G-505, the only guitars with pickguards.There are some ideas as to why the more expensive, classier G-808 never quite took off with the same following as the G-303.Aside from the fact that Pat Metheny is not dragging a G-808 out every night, the G-808 guitar seems slightly neck heavy when compared to the G-303.
There is no learning curve to the G-303, no time required to "get acquainted," this is a guitar you want to play as soon as you put your hands on it.
From looking at the version "A" photo, it appears the one op-amp is used per string to both amplify the signal and create the hex fuzz sound.
If you look at IC6, at the top of the version "B" and "C" card, you can see resistors just to the left of the chip creating gain in the negative feedback loop, and additional diodes just to the right side of the chip for generating fuzz. After years of working with Roland vintage electronics, I finally noticed that there were two variations on the familiar hex pickup.
In addition, the standard 1/4” output jack solders directly to the PCB, rather than the ribbon connector.
The first time I tried to repair a failed op-amp in a G-303, I realized that the pin-out documentation was wrong on the schematic.