Electro-Harmonix Hot Tubes OD

The Electro-Harmonix Hot Tubes OD is an overdrive pedal from Electro-Harmonix, first reissued in 2013 as a faithful, miniaturized re-creation of the company's original Hot Tubes, which dates back to 1978¹. Where most overdrives clip the signal with diodes or op-amps, the Hot Tubes is built around a CMOS overdrive circuit, the same approach as the 1970s original, and it was designed to replicate the organic overdrive of a vintage tube amp².

The CMOS circuit gives the pedal a wide dynamic range: press coverage describes it as able to deliver a fattened tone at lower gain settings or push an amp into dimed vintage territory with high sensitivity and a musical feel, without compromising or coloring the original tone³⁴. Guitar World's reviewer put the range in plainer terms, writing that the Hot Tubes Overdrive "covers the gamut from overdrive crunch to full-on raging distortion with a twist of its overdrive control"⁵.

An overdrive modeled on a vintage tube amp

The original Hot Tubes launched in 1978 as one of the larger, flatter EHX pedals of its era, a big box with three knobs⁶⁷. Its CMOS circuitry was chosen for the purpose of emulating a valve amp, an unusual approach at a time when most overdrives used simpler clipping stages⁶. Electro-Harmonix discontinued the original in 2009⁸, and by the time of the reissue the vintage units had become quite pricey and hard to find⁸⁹.

For the 2013 revival, Electro-Harmonix founder Mike Matthews says the company went back to the original schematic rather than redesigning it¹⁰:

The reissue, announced in August 2013, is housed in a compact die-cast nano-sized chassis, roughly one-quarter the size of the long-discontinued original³⁴⁶. Independent analysis backs up the claim of continuity: a DIY builder who compared the reissue against a home-built clone of the circuit reported "Very much the same sound"¹¹.

The controls: Volume, Overdrive, Tone and the Tone switch

The Hot Tubes OD keeps the three-knob layout of the original, plus one addition the 1978 big box did not have: a Tone On/Off switch⁷³. Each control, as described by Electro-Harmonix on the product page²:

The Tone control can add extra warmth or sizzle depending on where it is set¹². The Tone On/Off switch is the pedal's most distinctive feature: it completely removes the tone control from the pedal's circuit, so the overdrive reaches the output without any tone shaping in the way. Vintage Guitar described the result as a more-transparent sound, and Guitar World's reviewer called it a route to "pure, unadulterated overdrive"³⁵. JHS Pedals' retrospective on underrated EHX pedals singled out the switch as a practical touch, noting that "The nano version has the on and off for tone control, which is great"⁷.

Power and bypass

The Hot Tubes OD runs on a 9-volt battery, which is included in the box, and can also be powered by an optional standard 9.6-Volt/DC 200mA AC adapter, which is not included²³¹².

Bypass is true bypass, a point on which the maker and every press source agree: true-bypass switching preserves signal integrity while the pedal is not in use, so the Hot Tubes can sit in a chain without loading the signal when it is off²³⁴.

A reissue of the original Hot Tubes

The Hot Tubes family can be confusing because the name has appeared on more than one Electro-Harmonix product over the years⁷¹³¹⁴:

• The original Hot Tubes (1978): the big-box CMOS overdrive, discontinued in 2009⁸²
• The Hot Tubes OD / Hot Tubes Nano (2013): the compact reissue covered on this page, the same design miniaturized¹¹⁰
• A Hot Tubes Distortion/Sustainer: a separate, larger pedal with Master Volume, Gain, Drive, Bass and Treble controls, reviewed by Barry Rudolph at $278 MSRP¹⁴

The 2013 reissue was announced under the Hot Tubes Nano name, and it is the same pedal as the Hot Tubes OD: MusicRadar's review of the Hot Tubes Nano describes it as about one-quarter the size of the original with the CMOS circuitry apparently unchanged⁶. Electro-Harmonix's current product page sells it simply as the Hot Tubes, promising "the exact same tone and drive as the 1970s original"².

What reviewers made of it

Press reaction to the reissue was positive. Guitar World's review grouped the Hot Tubes with the Nano Big Muff Pi as reissues of classic Seventies EHX stomp boxes, both featuring true-bypass switching, and found the Hot Tubes spanned everything from crunch to full distortion⁵. MusicRadar's verdict on the Hot Tubes Nano was blunt in the best way: under "reasons to avoid" it listed simply "Not a lot"⁶. Vintage Guitar's coverage emphasized the value of having the 1978 circuit back in a modern, affordable package².

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