The Electro-Harmonix Hot Tubes name covers two related dirt boxes. The original is a CMOS overdrive from 1979 that Electro-Harmonix discontinued in 2009 and reissued in 2013 as the Hot Tubes Nano123. The Hot Tubes Distortion/Sustainer is a separate, tube-based unit: reviewer Barry Rudolph described it as using two New Sensor 12AX7 tubes to give overdriven sounds "like those from mild tube amps all the way to 'beyond distortion' as we now know it"4. Both sit in the overdrive and distortion family, and both were made by New Sensor Corporation, hand-made in New York City4.
The controls
The Nano reissue keeps the control set of the original CMOS pedal simple. Electro-Harmonix describes the two knobs as follows1:
| Control | What it does |
|---|---|
| OVERDRIVE knob | Controls the amount of input gain and distortion1 |
| VOL knob | Sets the output volume1 |
Guitar World's reviewer Chris noted that on the Nano the control on the upper right adjusts overdrive, sustain and drive5. The Nano also carries a Tone control, which Delicious Audio's announcement summed up as "Sculpt your sound with the Tone control"6. JHS Pedals, in a piece on underrated Electro-Harmonix pedals, pointed out a quirk of the layout: "The nano version has the on and off for tone control, which is great."7
The tube-based Distortion/Sustainer is a different animal. Barry Rudolph described a fuller control panel4:
- Master Volume
- Gain
- Drive
- Bass
- Treble
In his words, "You vary distortion, sustain and tone from vintage to modern with the Master Volume, Gain, Drive, Bass, and Treble controls"4. That five-knob set gives the tube version far more tone shaping than the two-knob CMOS pedal, with separate Bass and Treble controls rather than a single Tone knob.
Maker, status and the Hot Tubes Nano
The CMOS Hot Tubes dates to 1979, when it used hex inverters, the same class of chip Aion FX notes in other overdrive circuits of the era3. Guitar World has also reported that the pedal drew on an earlier Electro-Harmonix design, writing that the company "used the Tube Sound Fuzz in the late '70s to inform its Hot Tubes pedal"8. Electro-Harmonix discontinued the pedal in 20092.
In 2013 the company brought it back. Guitar World called the reissue "a faithful re-creation of the original design" presented in "a compact, nano-sized chassis"9, and Delicious Audio reported that the Nano "uses the exact same design as the original but in a much smaller case"6. MusicRadar's Trevor Curwen put the size difference in perspective: the Nano is about one-quarter the size of the long-discontinued original10. Vintage Guitar noted the Nano can be powered by an AC adapter11.
The Hot Tubes name spans two different products. The CMOS overdrive (1979, discontinued 2009, reissued as the Nano in 2013) is a compact pedal with no tubes in it. The Hot Tubes Distortion/Sustainer reviewed by Barry Rudolph is a larger, tube-powered unit at $278 MSRP. Check which version a listing refers to before comparing prices.
Electro-Harmonix marketed the Nano on continuity with the past, promising players the "exact same tone and drive as the 1970s original!"1. The company also pointed to a distinctive circuit feature, the paracyclic filter, which it credits with making the Hot Tubes "a most versatile distortion device"2. No further technical detail on the filter is published, so the term remains the maker's own.
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Johan Segeborn
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Questions
Is the Electro-Harmonix Hot Tubes still made?
The CMOS-based Hot Tubes overdrive was discontinued in 2009, and Electro-Harmonix brought it back in 2013 as the Hot Tubes Nano, a compact reissue using the same design. The tube-based Hot Tubes Distortion/Sustainer reviewed by Barry Rudolph was a separate, larger unit hand-made in New York City, listed at $278 MSRP.
What tubes does the Hot Tubes use?
The Hot Tubes Distortion/Sustainer uses two New Sensor 12AX7 tubes. According to reviewer Barry Rudolph, these produce overdriven sounds ranging from those of mild tube amps all the way to what he called beyond distortion. The CMOS-based Hot Tubes overdrive, by contrast, uses no tubes at all.
What is a paracyclic filter?
Electro-Harmonix describes the paracyclic filter as the Hot Tubes feature that makes it a most versatile distortion device. The company does not publish a detailed technical explanation of the circuit, so the term is best treated as the maker's name for the tone-shaping stage that sets the pedal apart from other distortion boxes.
Where was the Hot Tubes built?
The Hot Tubes Distortion/Sustainer was hand-made in New York City by New Sensor Corporation, the company behind both Hot Tubes and the Big Muff Pi. The CMOS Hot Tubes overdrive and its 2013 Nano reissue carry the Electro-Harmonix name, the brand New Sensor Corporation owns.
Sources (11)
- Hot Tubes, Electro-Harmonix
- Hot Tubes, Electro-Harmonix
- Runoffgroove UBE Screamer, Aion FX, 2022-04-08
- Big Muff Pi and Hot Tubes from Electro-Harmonix, barryrudolph.com, 2021
- Review: Electro-Harmonix Hot Tubes Overdrive, Nano Big Muff π and Soul Food Pedals, Guitar World, 2014-02-27
- EHX Releases Nano Re-issue Of Hot Tubes, Delicious Audio, 2013-08-21
- UNDERRATED ELECTRO-HARMONIX PEDALS, JHS Pedals
- Catalinbread sees the JHS Pedals Notaklön and raises the Knight School Overdrive, Guitar World, 2023-11-28
- Electro-Harmonix Reissues a Classic Rarity, Guitar World, 2013-08-22
- Electro-Harmonix Hot Tubes Nano review, MusicRadar, 2014-04-07
- E-H Reissues Hot Tubes OD, Vintage Guitar magazine, 2013-08-22
