The Keeley Super Phat Mod Germanium Anniversary Edition is a limited-run overdrive pedal that Keeley Electronics announced in 2017 to mark 16 years of the Phat Mod circuit. Where the regular Keeley Super Phat Mod uses JFETs that emulate old tube amps, this edition swaps in germanium transistors, which Keeley says produces "a more aggressively voiced overdrive with spongy compression and fuzz that only germanium transistors give"1.
Delicious Audio, reporting on the announcement, described the result as dynamic and expressive, capturing many layers of tube amp simulation in one pedal2. Gearnews similarly heard a more "amp-like" guitar tone than the standard version3. It is a limited run of roughly 100 units, with the first 100 hand signed by Robert Keeley himself234.
A germanium overdrive with layers of tube-amp feel
The pedal sits at the fuzzier end of the overdrive family. Delicious Audio called it a more aggressively voiced overdrive with spongy compression and fuzz from the germanium transistors, and quoted Keeley describing it as a dynamic overdrive2. Gearnews framed it the same way: the germanium stages push the Phat Mod design toward a more "amp-like" tone than the JFET-based original3.
One detail Gearnews flagged for collectors: the gold pedal graphics were printed with "AC128 Germanium" in the top right, though the pedal they examined actually contained a Tungsram AC125 germanium transistor3. Players comparing units may therefore find the label and the part inside do not always match.
The enclosure also carries anniversary markings that separate it from the regular pedal: a new badge with sixteen gold bars in the center circle and a germanium transistor badge12.
A limited run of 100 hand-signed units
Keeley announced the pedal as the 16th Anniversary Hand Built Germanium Edition, hand built with through-hole parts, and said the first 100 would be hand signed12. Gearnews reported that around 100 units were expected to be built and signed, and noted the run was limited because Keeley did not have unlimited stock of the vintage germanium parts3. MusicRadar confirmed the pedal was hand built and available at launch in September 20174.
This was a limited run built around a finite stock of germanium parts, so the Anniversary Edition is not a pedal you can expect to find new at retail. The later Retro version, released in 2019 at $179, is now listed as discontinued6.
How it relates to the regular Super Phat Mod and the Retro version
The family tree has three branches:
| Pedal | What it is | Key differences |
|---|---|---|
| Keeley Super Phat Mod | The regular gold pedal, a souped-up Boss BD-2 circuit | JFETs emulating old tube amps13 |
| Keeley Germanium Super Phat Mod | The 16th Anniversary Edition | Germanium transistors, hand built, first 100 signed, new badge12 |
| Keeley Retro Super Germanium Phat Mod | A 2019 Custom Shop limited edition | Simplified Level, Tone and Nitro controls, reworked secondary gain stage56 |
The Retro version, announced in August 2018, is at heart the same germanium Phat Mod design: Guitar.com described it as layering old-school fuzz tones over amp-like overdrive, based on Keeley's germanium amplifier design7. Keeley's Custom Shop tinkered with the secondary gain stage so the dynamics were more pronounced, and gave it a simpler control set of Level, Tone and Nitro5. It launched in 2019 at $179 and is now discontinued6.
On That Pedal Show, the presenters demoed the Retro version and found it cleaned up right away when the guitar's volume was rolled back, a behavior they attributed to the germanium parts. Mick also noted it reminded him a little of an old power booster, with lovely fuzziness and breakup when pushed8.
"Check out the way that cleans up on the volume."
Where the Phat Mod circuit came from
The Phat Mod story starts with the Boss BD-2 Blues Driver. Robert Keeley has said the circuit was the third one he modded, in 2001, after the ROSS Compressor and the Tube Screamer, and that he had "had the pleasure of modifying this circuit for many years"123. The regular Super Phat Mod was his souped-up production version of that modded BD-2 circuit, using JFETs to emulate old tube amps13.
The lineage has kept growing. Premier Guitar describes the Super Phat Mod as "a beefed up take on the beloved blues driver circuit"9, and Keeley's later Tube Drive pairs the Super Phat Mod circuit with a high-voltage tube preamp. For players tracing the BD-2 family, the Germanium Anniversary Edition is the branch where vintage transistors, rather than JFETs or tubes, do the work of shaping the gain.
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Questions
How many Keeley Super Phat Mod Germanium Anniversary Editions were made?
The Germanium Super Phat Mod was a limited run, with around 100 units expected to be built and signed. Keeley described it as a 16th Anniversary Hand Built Germanium Edition, and the first 100 pedals were hand signed. The run was limited partly because the vintage germanium parts needed to build it were not available in unlimited stock.
Is the Germanium Anniversary Edition different from the regular Super Phat Mod?
Yes. Both are overdrives built on the same Phat Mod lineage, but the Germanium Anniversary Edition replaces the JFET-based stages of the regular Super Phat Mod with germanium transistors, which Keeley says gives a more aggressively voiced overdrive with spongy compression and fuzz. It also carries a couple of visual changes, including a new badge with sixteen gold bars and a germanium transistor badge.
Is the Keeley Retro Super Germanium Phat Mod discontinued?
Yes. The Retro Super Germanium Phat Mod, a later limited edition built by Keeley's Custom Shop and released in 2019 at $179, is listed as discontinued. It was itself a variant of the germanium Phat Mod design, with a simplified Level, Tone and Nitro control set.
Is the Anniversary Edition hand built?
Yes. Keeley described the 16th Anniversary Edition as hand built with through-hole parts, and the first 100 units were hand signed. MusicRadar also reported the Germanium Super Phat Mod as hand built and available at launch.
Which circuits did Robert Keeley mod before the Super Phat Mod?
Robert Keeley has said the Phat Mod circuit, a souped-up take on the Boss BD-2 Blues Driver, was the third circuit he modded, in 2001, after the ROSS Compressor and the Tube Screamer. He had been modifying the BD-2 circuit for many years before the Germanium Anniversary Edition appeared.
Sources (9)
- Keeley Launches Germanium Super Phat Mod Overdrive, Premier Guitar, 2017-09-07
- Keeley Super Phat Mod Germanium Anniversary Edition, Delicious Audio, 2017-10-04
- Keeley mods a mod with Germanium Super Phat Mod 16th Anniversary overdrive, gearnews.com, 2017-09-12
- Keeley Electronics drops Germanium Super Phat Mod, MusicRadar, 2017-09-20
- Keeley Retro Super Germanium Phat Mod, gearnews.com, 2018-08-10
- Guitar Pedal X, Guitar Pedal X, 2024-01-26
- Keeley launches new germanium fuzz/overdrive stompbox, Guitar.com, 2018-08-10
- Keeley RS Phat Mod, JHS Unicorn V2, Dano Pride Of Texas, Thorpy Fat General, That Pedal Show, 2018-10-16
- Take a Thrill Ride with Keeley’s Tube Drive, Premier Guitar, 2026-09-08
