Guyatone GST-UO5 Ultron review

This pedal shows how versatile an envelope filter can be

  • £349
A fabulous sounding pedal.

MusicRadar Verdict

You can't move for envelope filters these days, but few can boast the warmth that the Ultron delivers.


  • +

    Meaty wah!


  • -

    It's not cheap.

MusicRadar's got your back Our team of expert musicians and producers spends hours testing products to help you choose the best music-making gear for you. Find out more about how we test.

Without a touch of wah, '70s porn soundtracks just wouldn't be the same. It doesn't matter how good/bad the action is, whack on a wah pedal fed by some Hendrix-style guitar and everything just seems to, er… slip into place, so to speak.

Wah has come a long way since those halcyon days of big moustaches and dubious plotlines and at first glance the Guyatone Ultron couldn't look further removed from those brick-like pedals of the '70s.

It's a lightweight but well-built beast that looks like it would be happier in the safe confines of a recording studio than onstage under a Converse trainer - those little panel switches and LED display should be treated with respect!

The Ultron's circuitry is based on the classic Mu-Tron III envelope filter of the 1970s and offers three main types of effects.

Two of them, as discussed in the pornographic opening paragraph, are wah effects - auto and manual. The remaining effect is an envelope filter controlled by the intensity of the input signal.

It's no surprise that Funk legend Bootsy Collins endorses the Ultron. Run any kind of bass signal through that envelope filter function and you'll see why the pioneering bassist describes the Ultron as "Da Bomb!" How's that for an endorsement?

Crashing back to Earth for a second, the cool thing about this pedal is that it combines the best bits of digital and analogue technology. It features a totally analogue audio path, which will please the vintage tone nuts, partnered with the functionality of digital.

So it's easy to adjust parameters quickly, and switching is silent enough to make the Ultron welcome in any recording studio. The front panel is intuitive, and if you're one of those people who hates reading operation manuals then you'll get a long way before you need to reach for the little book.


The problem with many wah units these days, including guitar effects pedals, is that they sound so damned weedy - a wah should sound fat and juicy. The Guyatone folk have obviously given tone a great deal of thought because (with apologies to another Japanese manufacturer) the Ultron sounds totally boss.

Both the Auto-wah and envelope filter functions are self-contained effects, while the Manual-wah mode requires the use of an optional expression pedal (Guyatone recommends that you use only the Boss FV-5, £49).

Unsurprisingly for a product that pays tribute to the Mu-Tron III the Ultron's envelope filter excels when you play 'choppy' Funk riffs, making it perfect for rhythm guitar tracks, slap bass and the kind of keyboard parts that Stevie Wonder made his own on songs like Higher Ground.

I also love the Auto-wah and the way it complements the instrument's tone rather than smothering it.

The Guyatone Ultron is not intended for guitarists who want to emulate only Jimi Hendrix. Oh no. The Ultron is for those musicians - be they guitarists, keyboard players, bassists or producers- who want an array of top-class filter effects handy in an easy-to-use package.

Future Music

Future Music is the number one magazine for today's producers. Packed with technique and technology we'll help you make great new music. All-access artist interviews, in-depth gear reviews, essential production tutorials and much more. Every marvellous monthly edition features reliable reviews of the latest and greatest hardware and software technology and techniques, unparalleled advice, in-depth interviews, sensational free samples and so much more to improve the experience and outcome of your music-making.