Introduced in 1995, the Bixonic Expandora is among many guitar and bassists favorite overdrive/distortion pedals. Probably made most famous by Billy Gibbons (ZZ Top), but also used by Bush, Megadeth, Joe Satriani, Bootsy Collins and countless others. It's been discontinued for quite a while now so I built this exact clone of one. After noticing its lack of low end, I modded it for no low end loss The originals had two internal dip switches to select the gain, and the second version moved them to the top of the pedal as slide switches. They later also added a guitar/bass slider switch but I found the 'guitar' mode pretty useless since it sounded way too thin, so I made mine to be permanently set in the 'Bass' mode for use as a full range overdrive/distortion.
It's somewhat similar to having a double Rat circuit (using two of the coveted LM308N opamps), but has a very unique 'opto' expander drive circuit using a Sharp PC419 opto device driven by an expatial (and rare) BJT transistor.
The gain toggles select from low to 'crunch mode (the first one is subtle), and the second one from low to high gain 'distortion' mode (not subtle!). When they're both in the up position, it is in the 'FORBIDDEN' mode, with and over the top amount of distortion.
The originals came in a round 'Tuna can' type of enclosure, but I mounted this one in a smaller polished 1590BB.