The Fender TBX Tone Control, Part 1 - Premier Guitar Sep 21, 2010A lot of people think of the TBX tone control as a treble boost, but that’s not quite accurate. The TBX control actually consists of a custom dual-ganged pot (aka a “stacked” or “stereo” pot), a resistor, and a capacitor that cuts the bass and treble out of the circuit, depending on which way you turn the knob.Author: Dirk Wacker Modified TBX Tone Control - Phostenix Wiring Diagrams Phostenix Wiring Diagrams. Search this site. Phostenix' Guitar Wiring Diagram Library. Here's a schematic of how the standard Fender TBX tone control is wired: As I drew it up, it seemed like what I needed was very similar to the Fender TBX tone control. It turns out that the Fender TBX is almost perfect for the job!