The Joker came from the idea, “what happens if you add controlled distortion to a normally clean booster?”. To achieve this, Flattley added an FET based 12AX7 valve simulation with the aim of sounding similar to an overdriven single valve combo.
However, on building a prototype it was found that the pedal had more uses than first envisaged. Firstly, it can do the “small amp tone” as expected. So in “dirt” mode anything from a “warm boost” to a “flat out tweed”. So jazz to blues covered.
A second range (“filth”) was added to allow gain / distortion for rock fans.
Third (unexpected) way of using it is as a boost for a conventional amp but with the added bonus of adding additional harmonic content / tone shaping before hitting the front end of the amp. This gives heavy rock fans the tones they are always looking for.
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