The Guyatone GST-UO5 Ultron is an envelope filter pedal that also works as an auto-wah and, with an expression pedal attached, a manual wah. MusicRadar's review describes its circuitry as based on the classic Mu-Tron III envelope filter of the 1970s, the design that set the pattern for this family of effects1. The Mu-Tron III was made by Musitronics and designed by Mike Beigel2, and it translated the volume profile of a player's picking into filter movement, the approach the Ultron carries on342.
What it does
The Ultron offers three main types of effect. Two of them are wah effects, auto and manual, and the third is the envelope filter mode proper1. An envelope filter, sometimes called an auto-wah, opens and closes a filter in response to how hard you pick, producing the vowel-like quack heard on funk records; the Mu-Tron III circuit it draws from is described in DIY documentation as "the classic Mutron III envelope filter (aka autowah)"5.
The manual-wah mode behaves differently: it requires the use of an optional expression pedal, and Guyatone recommends that you use only the Boss FV-5 for the job1. The other two modes respond to your playing dynamics without any pedal at all.
Sound and build
MusicRadar's reviewer was struck by the weight of the effect, writing "Meaty wah!" and noting that while envelope filters are everywhere, "few can boast the warmth that the Ultron delivers"1. The review characterizes the pedal's wah tones as sounding fat and juicy rather than weedy1.
The enclosure is described as lightweight but well-built, with a look the reviewer said would suit the safe confines of a recording studio rather than the stage. Switching is silent enough, the review says, to make the Ultron welcome in any recording studio1.
"It features a totally analogue audio path, which will please the vintage tone nuts, partnered with the functionality of digital."
Bootsy Collins endorsement
It is no surprise, MusicRadar's review concludes, that funk legend Bootsy Collins endorses the Ultron1. Collins's name is closely tied to the envelope filter sound, and the endorsement sits naturally with the pedal's Mu-Tron III lineage.
The manual-wah mode will not work without an expression pedal plugged in. Guyatone specifies the Boss FV-5 as the only pedal it recommends for this1.
Questions
Is the Guyatone Ultron analog?
MusicRadar's review describes the Ultron as having a totally analogue audio path, which the reviewer noted would please vintage tone enthusiasts, partnered with digital functionality for its features. So the sound-shaping circuitry is analog, while some of the pedal's control functions are handled digitally.
Does the Ultron need an expression pedal?
Only for one of its three modes. The auto-wah and envelope filter modes work on their own, but the manual-wah mode requires an optional expression pedal to sweep the filter. Guyatone recommends using only the Boss FV-5 expression pedal with the Ultron.
Which pedal is the Ultron based on?
The Ultron's circuitry is based on the classic Mu-Tron III envelope filter of the 1970s, according to MusicRadar's review. The Mu-Tron III was made by Musitronics and designed by Mike Beigel, and it remains the reference envelope filter that many later designs draw on.
Which expression pedal was recommended for the Ultron?
Guyatone recommends using only the Boss FV-5 expression pedal with the Ultron's manual-wah mode. MusicRadar's review listed the FV-5 at £49 at the time of writing.
Who endorses the Guyatone Ultron?
Funk legend Bootsy Collins endorses the Ultron, as MusicRadar's review notes. Given the pedal's fat, juicy wah tones, the reviewer called the endorsement no surprise.
Sources (5)
- Guyatone GST-UO5 Ultron review, MusicRadar, 2007-12-10
- Knight School Filter DIY Kit, Catalinbread Effects
- Beigel Sound Lab/Mu-FX Tru-Tron 3X Review, Premier Guitar, 2014-08-03
- Mu-FX Tru-Tron 3X™ Envelope Filter, pedal-of-the-day.com, 2016-04-19
- VFE_SPS_MiniMu.pdf, madbeanpedals.com, 2024-04-25
