Keeley Super Phat Mod

The Keeley Super Phat Mod is an overdrive pedal from Keeley Electronics, hand-built in the USA and built around specially selected JFETs¹. Its circuit is a refined and redesigned take on the Boss BD-2 Blues Driver, and it grew out of the Phat modification Robert Keeley spent years selling as an upgrade to that Boss pedal²¹. The pedal launched as the Super Phat Mod Full Range Overdrive in late 2016 at $149 in the USA and £149 in the UK from 15 December².

For a player, the pitch is a dynamic, amp-like overdrive. MusicRadar reported that the JFETs deliver natural break-up and dynamic tones highly responsive to pick attack, with Keeley reckoning he had "perfected" the design². Gearnews described it as designed to pick up the subtle nuances of your playing style¹, and guitar.com's reviewer found the touch sensitivity excellent, with the pedal cleaning up almost completely when the guitar volume is rolled back to about 7³.

A JFET overdrive built on the Blues Driver

The core of the pedal is its JFET (junction gate field-effect transistor) gain staging. Gearnews reported that the Full Range Overdrive uses specially selected JFETs¹, and guitar.com was told that the "magic" Toshiba JFET driving the gold enclosure took years to discover, allowing Keeley to design an overdrive with the same amp-like dynamics as the modded BD-2s he was known for³. Delicious Audio characterizes this as the transparent, dynamic JFET overdrive Keeley is known for, full of harmonic content⁵.

The BD-2 lineage matters to how the pedal behaves. The original Keeley Phat Mod for the Boss BD-2 upgraded internal components and added a dedicated switch that introduces additional bass and thickness to the pedal's natural overdrive⁶, with the beefed-up bass response selectable on most modded pedals via a small toggle switch added during the modification⁷. That idea survives in the standalone pedal as the Flat/Phat mode switch. On the modded BD-2, reviewers also noted a whole new level of output volume on tap, usable as a clean boost or to push a tube amp into almost-breakup territory⁷.

The Germanium Super Phat Mod variant used the same simple layout: Volume, Tone and Gain knobs plus a switch for Flat or Phat modes⁴.

Power and connections

The Super Phat Mod is true bypass, so it drops out of your signal path entirely when switched off³. Power comes from a 9V mains supply or a battery, and neither is supplied with the pedal³. It is a compact enclosure at 111 x 67 x 48 mm³, finished in a sparkly gold that guitar.com's reviewer thought would look more classy on a pedalboard than a modded Boss with a blue LED and an extra switch³.

From BD-2 mod to standalone pedal

The Super Phat Mod's history runs through Keeley's early business of modifying other makers' pedals. Robert Keeley started out in the FX business modifying existing circuits, one of which was the Super Phat mod for the Boss BD-2; the Super Phat Mod full range overdrive was announced as the latest evolution of that design². The mod itself upgraded the BD-2's internal components and added a dedicated switch that introduced additional bass and thickness to the pedal's natural overdrive⁶⁷. The standalone pedal is based on the modified BD-2 that played a big part in the growth of Keeley's reputation, though reviewers noted it is not just the same circuit in a non-Boss enclosure³.

The standalone pedal, announced in November 2016, combines all of his many upgrades to the BD-2 in one box¹. Gearnews called it basically a refined and redesigned Boss BD-2¹, while guitar.com noted that although it is certainly based on the modified BD-2 that played a big part in the growth of Keeley's reputation, it is not just the same circuit in a non-Boss enclosure³. Gearnews later described it as a Blues Driver with a sound all its own, released as a standalone pedal a good ten years after the mod first appeared⁹. At launch, Gearnews suggested it could be one to check out for anyone wanting a versatile overdrive with an already proven heritage¹.

Versions and editions

The Super Phat Mod family has several branches, most of them limited runs.

The Germanium Super Phat Mod, announced in September 2017, is a limited edition tweak on the Super Phat Mod featuring a Tungsram AC125 germanium transistor, which Keeley said sounded better for the pedal¹⁰¹². Because Keeley did not have unlimited stock of these parts, it was a limited run⁴. The 16th Anniversary Edition was hand built with through-hole parts and included a couple of visual changes over the regular pedal: a badge with sixteen gold bars in the center circle and a germanium transistor badge, the bars marking the mod's sixteenth anniversary¹¹¹²⁴. A collector detail: the gold graphics were printed with a reference to the AC128 transistor, which was switched out in favor of the AC125 at a late stage¹⁰⁴. Keeley described the result as a more aggressively voiced overdrive with spongy compression and fuzz that only germanium transistors give¹², and Delicious Audio called it dynamic and expressive¹¹. Gearnews judged it, from the demos, a decent sounding overdrive pedal for under $200, worth considering before stock ran out⁴.

The Retro Super Germanium Phat Mod, a Custom Shop pedal from 2018, is at heart the Germanium Phat Mod with the secondary gain stage tinkered with so the dynamics are more pronounced than the regular edition¹⁴. It is still based on a germanium amplifier stage, so it has amp-like qualities, albeit with a fuzz pedal in front of it¹⁴. Keeley's own press materials called it "a fuzz, it's a drive, and a cranked amp all in one"¹⁵, and Guitar.com described it as layering old-school fuzz tones over amp-like overdrive¹⁶. Its controls are Level, Tone and Nitro, plus a mini toggle choosing between Flat and Phat¹⁴, and it wore retro-inspired artwork by Phillip Ortiz over a textured, deep blue powder coat¹⁴. On That Pedal Show, the presenters found it at first "a bit thin" before finding the sweet spot, and noted how it cleans up on the volume control¹⁷. It shipped at $179 in limited quantities and is now discontinued¹⁴¹³.

The Super Phat Mod circuit also lives on elsewhere in the Keeley range: the mode toggle idea reappears in pedals like the D&M Drive line, where MusicRadar noted a variant toggling between Phat and an Andy Timmons AT mode instead of Flat and Phat⁸.

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