The Crazy Tube Circuits Unobtanium is a dual overdrive pedal that puts two of the most chased guitar sounds in one box: a faithful reproduction of the Klon Centaur circuit on the right side, complete with the germanium diodes that define its clipping, and a Dumble-style amp-in-a-box overdrive on the left123. Each side has its own footswitch, and both can be engaged together, so a player gets three footswitchable sounds from one pedal4.
Crazy Tube Circuits describes it as "a rare sonic element born out of legendary tones," and the maker positions it among its high-functioning two-in-one pedals: MusicRadar noted the brand "specialises in high-functioning twofers, such as its Unobtanium, which paired a Dumble-inspired preamp section" with a Klon Centaur-inspired overdrive51. The amp-in-a-box section is an all-analog circuit2.
The Klon-style side
The right channel is a faithful reproduction of the Klon Centaur overdrive circuit, using germanium diodes for clipping12. Its controls and switches:
| Control or switch | What it does |
|---|---|
| Volume | Sets overall output; a large amount of dB boost is available1 |
| Gain | Wide range, from transparent boost to high headroom overdrive1 |
| Treble | An active circuit that boosts or cuts treble1 |
| Bypass toggle | Chooses the original buffered bypass, which adds clarity and suits long cable runs, or true bypass1 |
| Clipping toggle (standard version) | Mod setting adds silicon diodes to the stock germanium diodes for higher output and less compression7 |
MusicRadar described the modded mode as "a modded mode with extra gain and headroom" compared with the standard Klon-style drive3. The buffered bypass option mirrors the original Klon Centaur units, which were buffered rather than true bypass10.
The Dumble side: SSS and ODS voicings
The left channel is a Dumble-style amplifier-in-a-box overdrive that emulates two Dumble amplifiers, selected with a two-way toggle switch11110:
- SSS (Steel String Singer): a clean and transparent overdrive with natural organic compression1
- ODS (Overdrive Special): a higher gain overdrive with enhanced mid frequencies and harmonic overtones1
MusicRadar's Jonathan Horsley wrote that "ODS adds a little more heat on the gain, boosting the mids and teasing out more juicy harmonic overtones"3. In guitar.com's review, Richard Purvis found that "SSS mode is where the really natural stuff happens, but it's worth flipping to the ODS setting for something with a thicker midrange," noting the ODS setting uses a pink LED rather than white4.
The Dumble side's controls are Volume, Gain, Tone and Emphasis210. There is also an external footswitch input jack to select the amplifier voicing, which bypasses the onboard toggle; the XT Footswitch is sold separately1. On the Raw Edition, an internal trimmer adjusts the output gain for ODS mode, giving an extra 6dB of gain to simulate driving the power tubes harder10.
Using both sides together
The two channels are stackable11. As guitar.com's reviewer put it:
"The ability to engage both sides of the Unobtanium together takes our total of footswitchable sounds up to three"4
That means the Klon side can serve as a boost into the Dumble side, or each can be used on its own, all from two footswitches48.
Power and connections
The Unobtanium runs on a 9V DC input only. The maker warns plainly: "Do not use a higher voltage power supply"1. The same warning applies to the Raw Edition7. The enclosure uses top-mounted jacks, which MusicRadar noted "should ease it onto your 'board"3.
The 9V DC-only power requirement means the pedal should be run from a suitable 9V supply, not a higher voltage unit. The buffered bypass mode on the Klon side is the better choice if you run long cables1.
History and versions, including the Raw Edition
The Unobtanium was released in 20226. In June 2024, Crazy Tube Circuits introduced the Unobtanium Raw Edition, a limited colourway version whose controls are unchanged apart from the Stock/OC45 legends on the Klon channel's clipping toggle8. The Raw Edition's Klon channel adds a Stock/OC45 toggle that uses a NOS Mullard/Valvo OC45 germanium transistor for deeper breakup, which the maker calls the first K-type circuit to feature germanium transistors78. On the Dumble side, the overall tone was tweaked to sound glassier rather than smooth, and the channel renders glassier and punchier than the standard version's smoother jazz/blues-oriented tones768.
The Raw Edition is built in limited quantities and stays available only for as long as the maker's stock of NOS Mullard/Valvo OC45 transistors lasts; it does not replace the standard version, which continues in production7. The Raw Edition was priced at $349 / €339 against $269 / €289 for the original sand-colored edition in June 20248.
What reviewers said
guitar.com reviewed the Unobtanium in February 2023 and rated it 9 out of 10, concluding4:
"A smartly designed dual overdrive with top-class tones on both sides."4
The review also confirmed the pedal's Greek manufacture and its 123 x 98 x 52mm dimensions4.
Videos
Pete Thorn
R.J. Ronquillo
Kris Barocsi
News
Questions
Is the Unobtanium a Klon Centaur clone?
The right side is a faithful reproduction of the Klon Centaur circuit, including the germanium diodes used for clipping. A Mod mode adds silicon diodes alongside the germanium ones for higher output and less compression. The left side is a separate Dumble-style amp-in-a-box circuit, so the pedal is two drives in one enclosure.
Can both sides of the Unobtanium be used at the same time?
Yes. Each channel has its own footswitch, and both can be engaged together, which guitar.com's reviewer counted as giving three footswitchable sounds in total: the Klon-style side, the Dumble-style side, and both stacked. The channels are described as a stackable dual overdrive.
Is the Unobtanium true bypass or buffered?
The pedal uses a click-less true bypass design with high quality relays. On the Klon-style side there is also a toggle switch that lets you choose the original buffered bypass, which adds clarity and suits long cable runs, or true bypass instead.
Where is the Crazy Tube Circuits Unobtanium made?
The Unobtanium is made in Greece, where Crazy Tube Circuits builds its pedals. The standard version continues in production, while the limited Raw Edition is built in small quantities for as long as the maker's stock of NOS Mullard/Valvo OC45 germanium transistors lasts.
Sources (11)
- Unobtanium, Crazy Tube Circuits
- Crazy Tube Circuits seeks to channel Klon Centaur and Dumble tones with its two-sided Unobtanium overdrive, Guitar World, 2022-12-07
- What do you get if you put two Dumble-style drive voicings and a faithful Klon clone in one deluxe dual-channel pedal?, MusicRadar, 2022-12-09
- Crazy Tube Circuits Unobtanium review, guitar.com, 2023-02-13
- “Imagine standing in front of a wall loaded with tube amp heads and 4x12 speaker cabinets, grabbing your guitar and hitting a chord”: Crazy Tube Circuit's Heatseeker is an amp-in-box to help you nail Angus Young's high-voltage AC/DC tones, MusicRadar, 2024-12-10
- Crazy Tube Circuits Unobtanium Raw Dual Drive, Delicious Audio, 2025-02-24
- Unobtanium Raw, Crazy Tube Circuits
- Guitar Pedal X, Guitar Pedal X, 2024-06-11
- Crazy Tube Circuits Limited Edition Unobtanium RAW Overdrive, gearnews.com, 2024-06-11
- “We have tried many germanium transistor types and found that the OC45 transistors added a supernatural feel”: Crazy Tube Circuits cooks up a tasty Dumble/Klon stew with the Unobtanium Raw, MusicRadar, 2024-06-11
- Crazy Tube Circuits Unobtanium Dual Drive, Delicious Audio, 2022-12-06
