String Theory EFX KE/64 Overdrive

The String Theory EFX KE/64 Overdrive is the debut guitar effect pedal from String Theory EFX, an Illinois-based effects company¹. It is an overdrive pedal built around a JFET transistor circuit, and its voicing is inspired by the sound of a cranked-up little green British combo amplifier². The design goal, as Premier Guitar reported at the launch, was to keep the original sound of your guitar and amplifier intact while adding a little "something special" and delivering organic, amp-like overdrive¹.

In practice, the KE/64 covers a wide gain range. Premier Guitar described it as running from a subtle clean boost up to a low-to-medium gain overdrive, with the actual level of gain depending on the output of the pickups in your guitar¹. It can be used on its own or stacked with other overdrive and fuzz pedals for more gain staging options¹.

How it is built

The original KE/64 was built the labor-intensive way. Premier Guitar's launch coverage described it as 100% hand-wired on perfboard in the U.S.A., with no PCBs or SMD parts, and the controls, stomp switch and jacks were all wired using high quality, vintage style cloth covered wire¹. The knobs are solid aluminum, American made¹. The enclosures on the original effects were acid etched by hand³.

In April 2019, String Theory EFX announced an updated version that changed the construction. As Premier Guitar reported, both the KE/64 and its sibling, the Tevatron Fuzz, moved to printed circuit boards and powder coated enclosures with UV printed graphics, replacing the point-to-point wiring and acid etching of the originals³. Guitar World noted the updated pedals are still hand-wired and are now more pedalboard-friendly⁴.

Versions and price

The updated version was announced on April 19, 2019, and both Guitar World and MusicRadar reported it as available now at $165³⁴⁵. That is $85 less than the original 2018 price, a drop from $250 to $165¹³.

Warranty and build quality

All String Theory EFX pedals are hand-built and carry a lifetime warranty². The circuits are all-original designs, not clones, as MusicRadar's Michael Astley-Brown noted when the company unveiled its first effects².

Where it came from

The KE/64 Overdrive and the Tevatron Fuzz were the first two pedals from String Theory EFX, announced in August 2018 as the company's debut all-original effects¹. The KE/64's JFET-based circuit was inspired by a cranked-up little green British combo amplifier, an amp-in-a-box approach aimed at players who want amp-like breakup without pushing a real amp hard². For players comparing gain stages, it sits on the lower end of the gain spectrum compared with distortion and fuzz pedals, and its clean-boost range also puts it in conversation with dedicated boost pedals.

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