A YouTuber has built a pedal to clone Kurt Cobain’s home demo tone

Aaron Rash's Kurt Cobain The Engine Pedal
(Image credit: Aaron Rash / YouTube)

For those of you not familiar with Aaron Rash, he’s a producer and musician who runs a channel on YouTube that is largely dedicated to Nirvana’s guitar tone. 

In his latest video, Rash explains that there had been a sound that had long eluded his tonal investigations, something he heard on Kurt Cobain’s home demos but was unable to replicate using the usual distortion pedals associated with the Nirvana icon.

A resourceful, hands-on type, Rash took to his soldering iron in an effort to build a box that captured the sound. The result is a pedal he calls The Engine, because “to me it sounds like an engine, revving to the max, about to explode into a million pieces… it’s a really weird sound.”

Rash admits the design and the sound are both unorthodox, but that’s largely the point. 

“If some smart, super-awesome designer guy came in here and saw this pedal, he would slap me in the face,” explains the guitarist. “Everything from a technical standpoint is wrong. I biased it wrong. I wired things up really strange. It’s all super old stuff, wired point-to-point, ‘70s-style.”

The controls are limited to Volume and Roar, and when cranked up it has an appealingly growly, serrated tone, but back it off and the effect comes very close to the static-y asymmetrical clipping sound of Cobain’s gnarly Heart-Shaped Box tone – captured using a Fender Quad Reverb guitar amp with only a single power tube.

In the clip, Rash explains that he believes he recently found the source of his pedal mystery – pointing to Univox Super Fuzz from the ‘70s that Cobain once owned. However, the prohibitive price point ($1,000) will put many fans off that particular purchase.

Instead, Rash says he’s now considering producing The Engine for sale and perhaps even tweaking it to better incorporate the Ring Modulation-like tone of the Quad Reverb rig, too. 

Nirvana tone hounds will also be interested in another pedal that Rash teases at the close of the clip – a Red-X Ring Modulator built and hardwired by Mr. Bill. It is a direct clone of the one used by Cobain on Nirvana's In Utero.  

Mister Bill Red-X Ring Modulator

(Image credit: Aaron Rash / YouTube)

Rash claims (and Mr. Bill’s markings on the pedal innards would seem to confirm) that this makes it the “second one that exists in the world… the first one belongs to Steve Albini.”

In other Nirvana-based distortion news, Kurt Cobain’s Boss DS-1 pedal recently sold at auction for $75,000, which makes that Univox Super Fuzz price tag seem almost reasonable…

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Matt Parker

Matt is a freelance journalist who has spent the last decade interviewing musicians for the likes of Total Guitar, Guitarist, Guitar World, MusicRadar, NME.com, DJ Mag and Electronic Sound. In 2020, he launched CreativeMoney.co.uk (opens in new tab), which aims to share the ideas that make creative lifestyles more sustainable. He plays guitar, but should not be allowed near your delay pedals.