This mod brings the dual tonality of clean and a high gain distortion. The distortion is modified for smoother tone at low gains and better mixed sound. The tone control also gets a new mode for smooth tones and the bypass system is improved.

The added Clean Mix control is a volume control for the clean tone, and is completely independent of the distortion controls. The combination of this control and the distortion Volume creates the mix. The Gain and Tone controls allow combining different dirt tones with the clean. The clean signal range is from OFF to a +6 dB boost over bypass. Since the distortion also is capable of an almost-clean boost, when added together it makes for a versatile booster.

The new Tone circuit places the bassiest setting near the center of its sweep. Progressing clockwise is similar to the original circuit, which boosts bass and treble, creating a "scooped" midrange. But when turned "down" instead, it boosts midrange with a smoothed-off high end (this still de-emphasizes bass enough that it can be used to balance the tone from high to low). In particular, this makes for a lovely effect of smooth, sustaining distortion when mixed with the clean.

The clean mix mod is more complex than the Zombie mod, requiring the addition of an additional circuit stage for the mixing. Even so, the Supra circuit board welcomes this mod with a nice little space to mount it, surrounded by relevant signals.

Full mod list:
THICKER bass. SMOOTHING circuit. Distortion TEXTURE changes. These changes make for a less aggressive pedal than originally, but almost as metal on USABLE settings, and much better for other sounds.
Dual function TONE control. MIX stage and controls. 3 BYPASS mods: increased input impedance (less load on your pickups), anti-bleed, and improved components, resulting a top-quality silent-switching, buffered bypass.
GAIN mod: there are actually 2 versions (at least) of the FX55C. One has ten times as much gain as the other, but the low gain settings are difficult to control on the high gain version. Diplomatically, I'm changing the gain control (hence the new knob) on both versions to one that allows the gain and tone quality of the high gain version, but with smooth adjustment.

See soundclips and pricing below._2.mp3

This turns a mild-mannered distortion pedal into a unique and versatile fuzz -- and a great value. Features scary "zombie" fuzz, turbulent, dynamically responsive synth-like tones, "mixey" light overdrive + fuzz tones, and industrial metal sounds. It can also be used as a overdrive down to dirty boost, and its gated overdrive enables crazy boosting with controlled feedback.

The Supra uses two stages of distortion and the first is modified for a good overdrive style circuit with improved bass and wider gain range. In overdrive circuit style, there is a clean signal component at all times mixing inphase with the distortion. This becomes the primary distortion signal, and the added Mix control adds in the second stage of distortion, reversed in polarity (antiphase), subtracting from the lower level of distortion, so that the differences between the distortions can be emphasized and the common signal can be eliminated.

Revision 2 of my mod includes new improvements from my Clean Mix project, with no price increase: improved gain, even better bypass, better tone, and a dual-action Tone control -- since the Zombie mod produces a wider range of tonalities to compensate for, the new "left side" Tone control mode simply allows a flatter response (i.e. variable tone control bypass). The Zombie modification does not produce any of the original sounds of the pedal.