Picked up a used early version of the Keeley Java Boost that they no longer make any more. Early Silver Version uses Mullard OC44 Germanium transistors.
It is a Treble Booster by design, not a typical overdrive or distortion pedal. That means, the higher the note played, the more it gets amplified… and then, by your amp, distorted. Bass Notes get Cut in two of the modes on the Java Boost. Think Brian May style sounds. But it can do more. Different sound than what a tube screamer, Blues Driver or clean boost gives you. Designed to give you classic tones from the 60’s and 70’s. Great boost for your main overdrive pedal. The 3-way toggle can give you 3 distict settings ranging from mild to that old Sabbath sound when paired withy the certain amps or in combination with an overdrive pedal.
It is most widely used with a tube amp set to a bit of overdrive or clipping. That is the key to getting a great sound from this pedal. The toggle switch allows you to select from a classic Dallas Range master tone, mid boost, or full range boost. The other controls are Level and Tone.
The Java Boost is loosely based on the old vintage Dallas Rangemaster-type treble boost pedal that are quite rare and sell at vintage crazy prices if found intact. Keeley has made a few improvements, but used the same old Mullard OC44 transistor inside.