Crazy Tube Circuits Unobtanium review

Dumble and Klon-inspired tones united in one awe-inspiring overdrive pedal

Crazy Tube Circuits Unobtanium
(Image: © Future / Olly Curtis)

Guitar World Verdict

A versatile dual-drive pedal that will provide classy enhancement for your amp with flexibility of operation that runs from a transparent boost to full-fat overdrive.


  • +

    Two sought-after sounds in one pedal.

  • +

    Effects loop.

  • +

    External footswitching facility.

  • +

    Compact size for a twin footswitch pedal.


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Among all the rare gear that goes for silly money and deserves the ‘unobtainium’ moniker, an original Klon Centaur and a Dumble guitar amp are prime contenders. So how about a dual-footswitch drive pedal (for around $300) that aims to deliver the tonal essence of both?

On the left side you get the D-style sounds, and on the right there’s the K-type. Normal signal flow is the K feeding the D, but there’s a send and return loop for routing flexibility, inserting other pedals between the two, or having them as independent effects via a switcher. 

The K-type side is said to be an accurate recreation of the original circuit with the same germanium diodes, but you do get a couple of toggle-switched variations: a choice of true bypass or the original’s buffered bypass; and either stock circuitry or a more open-sounding modification that offers more output and less compression. 

The D-style side gives you a toggle-switched choice of two Dumble amps – the Overdrive Special (Robben Ford, Larry Carlton) or the cleaner glassier tones of the Steel String Singer (SRV). If you wish to be able to footswitch between the two, there’s an external footswitch jack to which you can add CTC’s dinky little XT switch.

Crazy Tube Circuits Unobtanium

(Image credit: Future / Olly Curtis)

The Klon-like kloning here is of high quality and does exactly what you’d expect, delivering classy transparent clean boost and overdrive to elevate your tone to the next level.

While we obviously don’t have a real Dumble for comparison, the D-type sounds offer the typical flavour of a defined low-end, fulsome midrange and sweet top with variations via an Emphasis knob that adjusts the EQ before the drive section and can really push the presence. There’s also a Tone knob for the high-end at the output.

You’ll find some characterful cleans here offering an instant upgrade on your tone, but many players will gravitate to the rich yet articulate drive tones, which have a dynamic sensitivity that makes them a joy to play through. Both sides work great individually; the K giving the D a boost works spectacularly well.


Crazy Tube Circuits Unobtanium

(Image credit: Future / Olly Curtis)
  • PRICE: £249
  • ORIGIN: Greece
  • TYPE: Drive pedal 
  • FEATURES: True bypass
  • CONTROLS: (Amp) Volume, Gain, Tone, Emphasis, ODS/SSS switch, Bypass footswitch, internal EQ and Volume Boost trimmers; (Drive) Volume, Gain, Treble, Buffer/True switch, Stock/Mod switch, Bypass footswitch
  • CONNECTIONS: Standard input, standard output, standard send, standard return, standard footswitch jack
  • POWER: 9V DC adaptor (not supplied) 
  • DIMENSIONS: 122 (w) x 95 (d) x 53mm (h)
  • CONTACT: Crazy Tube Circuits

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Trevor Curwen

Trevor Curwen has played guitar for several decades – he's also mimed it on the UK's Top of the Pops. Much of his working life, though, has been spent behind the mixing desk, during which time he has built up a solid collection of the guitars, amps and pedals needed to cover just about any studio session. He writes pedal reviews for Guitarist and has contributed to Total Guitar, MusicRadar and Future Music among others.