The Electro-Harmonix Hot Tubes is an analog overdrive pedal from Electro-Harmonix, first released in 1978 and reissued in 2013 in a compact nano chassis. Despite the name, there are no vacuum tubes inside: it is a CMOS overdrive, a circuit built around logic chips that EHX says was designed to replicate the organic overdrive of a vintage tube amp12.
The current version lists at $79.80 and runs on a 9V battery or an optional 9.6VDC-200mA adapter1. EHX describes its range as going from a gentle rasp that caresses your notes to a full-blown gain monster with a powerhouse punch, and says the pedal is sensitive to your touch and your guitar's volume control1.
The controls
The Hot Tubes keeps the control set simple: three knobs, one mini-toggle, and a footswitch.
| Control | What it does |
|---|---|
| Volume | Sets the output volume1 |
| Overdrive | Controls the amount of input gain and distortion1 |
| Tone | Controls a range of tones from warm bass to bright treble1 |
| Tone On/Off switch | Disengages the tone circuit for a more powerful, direct tone1 |
| Footswitch and LED | Selects effect mode or bypass; the LED lights when the effect is engaged1 |
The Tone switch is the one control that sets the pedal apart from a standard three-knob overdrive. With the switch set to OFF, the Tone knob is disabled, resulting in what EHX calls a more powerful, direct tone; set to ON, the Tone knob behaves normally1. Premier Guitar described the off setting as a beefier, more transparent sound, letting the player disengage the tone circuit entirely2, and Guitar World's reviewer called it a mini-toggle that completely removes the tone control from the pedal's circuit for pure, unadulterated overdrive5.
Power: 9V battery or 9.6V adapter
The pedal ships with a 9V battery installed, and can also be powered by an optional standard 9.6-Volt/DC200mA AC adapter, which is not included12. Current draw is 18mA1. The 2013 announcement listed the same arrangement: a 9-volt battery plus an optional 9.6-Volt/DC200mA adapter2. Guitar World's review noted a nine-volt adapter jack and a bright red status LED on the enclosure5.
The 18mA current draw figure comes from EHX's current product page1. The 200mA figure quoted in the 2013 press material describes the optional adapter's rating, not the pedal's own draw2.
History: a CMOS overdrive first released by EHX in the late 1970s
The original Hot Tubes launched in 1978 as one of the larger, flatter EHX pedals6. It was built around CMOS circuitry with the purpose of emulating a valve amp6, and Aion FX's technical write-up of related circuits notes the Hot Tubes used hex inverters, a common approach for 1970s CMOS drive pedals.
The original went on to become a rarity. EHX says that with the price of vintage Hot Tubes soaring, countless guitarists requested a re-issue of the 1970s pedal1. The reissue arrived on August 22, 2013, in a compact nano-sized die-cast chassis2. In the reissue announcement, EHX founder Mike Matthews said the company had used the exact same design and miniaturized it7.
Big box, nano and reissue versions
There are two main versions of the Hot Tubes:
- Original big box (1978): a larger, flat EHX enclosure with three knobs63. Barry Rudolph's review of the big box Hot Tubes Distortion/Sustainer describes Master Volume, Gain, Drive, Bass and Treble controls for varying distortion, sustain and tone from vintage to modern.
- Nano reissue (2013 onward): a compact die-cast package about one-quarter the size of the original, with the CMOS circuitry apparently unchanged68. JHS Pedals' rundown of underrated EHX pedals notes the nano version adds the on and off switch for the tone control3.
The reissue is a faithful re-creation of the original design, miniaturized27. MusicRadar's Trevor Curwen reported that the original was based around CMOS circuitry and is apparently unchanged in the new version6. Independent builder mirosol, writing on Tagboard Effects, compared an original EHX Hot Tubes nano against a self-built clone and found them very much the same sound9.
A related page covers the Hot Tubes Nano version in detail.
What reviewers said
Guitar World's 2014 review of the Hot Tubes Overdrive (list price $77.38 at the time) found it covers the gamut from overdrive crunch to full-on raging distortion with a twist of its overdrive control, delivering a full range of textures from crisp crunch to face-melting distortion with a significant volume boost5.
MusicRadar's review of the Hot Tubes Nano listed "great for sustain" and "a welcome return" among its reasons to buy, and found not a lot to avoid6. JHS Pedals highlighted the pedal as one of EHX's underrated designs, noting the nano version can be picked up used on Reverb for about $403.
Videos
EHX
EHX
Reverb
Questions
Is the Electro-Harmonix Hot Tubes true bypass?
Yes. Electro-Harmonix lists the Hot Tubes with true bypass, and the 2013 reissue announcement described true bypass switching that preserves signal integrity while the pedal is not in use. Reviewers at Guitar World also confirmed true-bypass switching on the pedal.
What does the tone on/off switch on the Hot Tubes do?
It disengages the tone circuit. With the switch off, the Tone knob is disabled and the pedal gives what EHX calls a more powerful, direct tone. Premier Guitar described the off setting as a beefier, more transparent sound, so you can run pure overdrive with no tone shaping in the path.
Are there tubes inside the EHX Hot Tubes pedal?
No. Despite the name, the Hot Tubes is a CMOS overdrive built around logic chips, not vacuum tubes. It was designed to replicate the organic overdrive of a vintage tube amp, and the reissue keeps the same CMOS circuitry in a compact die-cast package.
Is the Hot Tubes reissue the same circuit as the original?
Electro-Harmonix says the reissue is a faithful re-creation of the original 1978 design, miniaturized into a nano chassis. Mike Matthews said the company used the exact same design, and MusicRadar's reviewer reported the CMOS circuitry is apparently unchanged in the new version.
Sources (9)
- Hot Tubes, Electro-Harmonix
- Electro-Harmonix Reissues The CMOS Hot Tubes Overdrive, Premier Guitar, 2013-08-22
- UNDERRATED ELECTRO-HARMONIX PEDALS, JHS Pedals
- EHX Releases Nano Re-issue Of Hot Tubes, Delicious Audio, 2013-08-21
- Review: Electro-Harmonix Hot Tubes Overdrive, Nano Big Muff π and Soul Food Pedals, Guitar World, 2014-02-27
- Electro-Harmonix Hot Tubes Nano review, MusicRadar, 2014-04-07
- Electro-Harmonix Reissues a Classic Rarity, Guitar World, 2013-08-22
- Demo Video: Electro-Harmonix CMOS Hot Tubes Overdrive Pedal, Guitar World, 2013-09-24
- Guitar FX Layouts: EHX Hot Tubes, tagboardeffects.blogspot.com (Guitar FX Layouts), 2014-07-28
