Bixonic Expandora

The Bixonic Expandora is a distortion pedal first released in 1995 by the Japanese builder Bixonic, renowned for its circular "hockey puck" enclosure¹²³. It is a multi-distortion box: Vintage Guitar called it "a distortion box par excellence," and Pedal of the Day describes its range as running from subtle overdrive to heavy fuzz³². Aion FX calls it a Japanese boutique pedal, one of the first ultra-flexible dirt boxes, and notes it had four major versions during its original Bixonic production⁴.

What made it unusual for its day was that its most important controls were hidden inside. On the surface it offers gain, tone and level knobs, but a pair of internal dip switches optimizes the circuit for distortion or overdrive, and those settings open up a much broader palette of sounds³⁵.

What the Expandora does

The Expandora covers ground from overdrive through distortion to fuzz in one box. Pedal of the Day calls the range of sounds you can squeeze out of the silver disc-shaped unit "nothing short of incredible" despite its basic-looking controls². Delicious Audio describes the vintage pedal as one of the first ultra-flexible dirt boxes⁷.

Vintage Guitar's 1996 review, testing it with a Strat through Fender amps, found the sound "raunchy, with definite tube tone and a nice presence when the volume is rolled down a tad," and that a stock reissue Les Paul yielded a fatter tone and gobs of distortion³. The reviewer also found the dip-switch settings gave a broader palette of distortion, including authentic fuzz³.

The pedal's reputation has kept it alive long after the original run ended. Aion FX notes it was a favorite of Billy Gibbons of ZZ Top⁴, and Guitar Pedal X's Stefan Karlsson calls Gibbons "the perfect ambassador for this genre," naming the Expandora 2000R as his favorite⁸. The circuit has also been kept alive by builders and cloners, from the Expandora Squared reissue to the Decibelics Reverend V1 Mini Expandora⁹¹⁰.

Gain, tone, level and the dip switches

The original Expandora keeps its visible controls simple: gain, tone and level knobs on the face³. The real flexibility lives on a pair of internal dip switches, which let the player optimize the pedal for distortion or overdrive⁵. Vintage Guitar's reviewer found that playing with the dip switches "did indeed give a broader palette of distortion," including fuzz the reviewer described as authentic³.

On the 2000R, the third control, Output Level, balances volume between the distorted and bypassed signals⁶.

Two cascaded gain stages

Under the lid, the Expandora is not a copy of any one pedal, but it has a clear lineage. According to Aion FX, the circuit originated from an experiment in putting two RAT Distortion pedals in series: it uses two cascaded LM308 or OP07 gain stages, essentially as if two Rats were chained together⁴. That explains why it is related to the Rat family without being a Rat clone.

The twist is what happens around those gain stages. A side-chain envelope detector engages an opto-FET as the op-amp's gain control, so the gain structure responds to the input signal in a way a plain cascaded distortion does not⁴. This is the design feature DIY builders keep returning to; Aion FX, Madbean Pedals and GuitarPCB all document Expandora-derived projects⁴¹.

Power: nine-volt

The original Expandora runs on a nine-volt battery that rests smack in the middle of a cutout in the circuit board; there is no true battery compartment³. The 2000R can be powered by a battery or a recommended 9-volt power supply, with a Phillips screw removing the plate for battery access⁶.

Versions and the 2000R

The Expandora had four major versions during its original Bixonic production⁴. The ones the record names:

The 2000R moved the mode selection outside. Its D1 and D2 switches give four combinations, both down, one up, or both up, for Crunch, Overdrive, Distortion and Fuzz varieties⁸. With both switches up, Karlsson describes a rich Harmonic Fuzz, or "Fuzzstortion," in what users call the Forbidden Mode⁸. Vintage Guitar likewise found that D2 in the high position delivers a fat, over-the-edge fuzz known to Expandora users as the "forbidden zone," and that D2 alone adds more gain than D1 alone⁶.

The name has since been revived by a US company that bought the Expandora name, which reissued the circuit as the Expandora Pedals Vintage Reissue Overdrive Distortion Fuzz and built the Bixonic Expandora Squared, made in the USA with enhancements to the original schematic for improved headroom⁹¹¹. The Squared runs on 9V DC center negative at 15mA, is custom made in batches, and uses original-spec silicon clipping diodes¹¹.

What reviewers said

Vintage Guitar reviewed the original in May 1996 and the 2000R in July 2007, and both reviews were positive. Of the original, the reviewer wrote:

Of the 2000R:

The 2000R review also noted the pedal is capable of extremely fat or thin fuzz, and concluded it was money well spent⁶. Pedal of the Day, reviewing the Vintage Reissue in 2026, found the range of sounds incredible for the unit's size and basic-looking controls². Guitar Player has counted the Expandora among its top 50 stompboxes of all time, citing its ability to be optimized for distortion or overdrive via the internal dip switches⁵.

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