Guyatone Ultron GST-U05 Optical Auto Wah and Ultrem GST-C04 Optical Tremolo

The Guyatone Ultron and Ultrem optical pedals are the brainchildren of celebrated engineer and designer Hideko Shimizu, who passed away in late 2004, while the pedals were still in the final stages of development.
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“Guyatone had created prototypes of the two pedals, which they had me run by several professional artists to get their feedback,” relates Kevin Bolembach, effect consultant and president of Godlyke Distribution (Guyatone’s U.S. distributor). “We compiled all of the artists’ suggestions and sent them back to Mr. Shimizu in Japan, who became excited about expanding the products from simple vintage-style optical effects to units with lots of advanced capabilities. Although we had to do some reverse engineering—and other detective work—to bring them to completion after Mr. Shimizu’s untimely death, the Ultron and Ultrem pedals ultimately became high-end analog units with digitally controllable parameters and simple user interfaces.”

To achieve the highest possible audio quality and functionality, Shimizu designed several custom components—including low-voltage photocouplers hand-wound to specific tolerances, CPU sections featuring variable-speed oscillators with tap-tempo capabilities, six selectable waveforms, multiple effect modes, and expression pedal control of a variety of parameters. Despite their robust feature sets, however, the Ultron and Ultrem are remarkably ergonomic, and once you familiarize yourself with the functions of their various knobs, switches, and LEDs, their operation is relatively straightforward. In other words, you don’t have to be an inveterate tweaker to coax great sounds out of them. I tested the two pedals with various guitars and amplifiers, as well as using them as outboard effects in my studio.

Ultron GST-U05 Optical Auto Wah

As suggested by its name, the Ultron is based on the classic Mu-tron III envelope filter pedal. The Ultron offers the same Low-Pass, Band-Pass, High-Pass, and Notch filter types (the latter is included on the current Mu-Tron III+), a Peak control for adjusting how pronounced the effect is, a Drive switch for determining whether the filter sweeps up or down, and an expanded Range switch that adds Midrange to the Mu-Tron’s choices of High and Low ranges. The Ultron also has Threshold and Frequency controls, which provide more precise control over the behavior of the filter, and instead of a single waveform, you have a choice of Triangle, Saw-Tooth, Reverse Saw-Tooth, and three types of Square waves. Additionally, there’s an onboard digital oscillator—with values displayed either in milliseconds or BPM—and an expression-pedal jack.

All of this controllability results in three distinctly different types of wah effects: envelope-controlled Touch Wah for Mu-Tron-type sounds, oscillator-controlled Wave Wah with tap-tempo for rhythmic effects, and Pedal Wah, which works with an optional expression pedal. The Effect Mode section offers a choice of six modes, but four of them have “sub” modes, and two have additional “hidden” modes, for a total of twelve. There’s even a switch that adjusts the response of the Tap function (1x, 2x, or 4x the tapped interval), and the sweep curve of the expression pedal (Audio, Linear, and Reverse Audio). And did I mention the four DIP switches and Threshold Trimmer pot located inside the pedal that are used to fine-tune the response to specific instruments?

The four filters have a fat, warm sound that is reminiscent of a vintage Mu-tron III, but with the added clarity and bite of, say, a Moogerfooger MF-101 Low-Pass Filter. The oscillator responds precisely to tapped-tempos, and may also be set manually across a huge range of speeds (15-840 bpm/70-4000ms). The envelope follower easily tracked every nuance articulated in my picking.

As cool as the stand-alone effects are, to unlock the full power of the Ultron you’ll need to have an expression pedal. (Guyatone recommends the Roland EV-5 only, but Moogerfooger and M-Gear pedals worked fine.) Besides controlling parameters such as depth and oscillator speed, you can also switch between waveforms on the fly, and manually sweep the filters for wah-pedal effects.

To describe all of the sounds that are possible with the Ultron would take pages of print, but suffice to say that after using the Ultron extensively for two months, I was able to create nearly any filter sound I could imagine—including classic funk pops (think Bootsy Collins), far out pedal sweeps, tempo-synched auto-wahs, synth-like textures, and bizarre special effects—and all with negligible noise. If filter sounds are important enough to you to justify investing in a professional-grade device, the Ultron is an excellent choice. For others, it may simply be too much of a good thing.

Ultrem GST-C04 Optical Tremolo

The Ultrem looks and functions much like the Ultron, and employs the same analog-digital hybrid typology, a similar control layout, the same six selectable waveforms, six Effect Modes (with another six available, as per the Ultron), and many of the same switching options. And, as with the Ultron, you’ll need an expression pedal to access several of the modes. The Ultrem can operate in stereo, however, so you will want to run it in that configuration if you wish to take advantage of its auto-panning capabilities.

The Ultrem has four primary controls that function in all operational modes. Depth varies the overall amount of the effect from zero to 100 percent, unless the Blend switch is engaged, in which case a fixed amount of the unaffected signal is always present. This helps to preserve the attack transients that are sometimes lost when using full-on tremolo effects. When the Ultrem is configured in stereo, engaging the Pan switch causes the sound to cycle between two amps or speakers at a selectable rate. The Saturation knob dials in varying amounts of distortion to simulate the sound of overdriven tube-powered tremolo units.

With the Ultrem connected to two amps (or mixer channels panned hard right and left), I was able to get every shade of tremolo imaginable, including oscillator or pedal-controlled auto-panning trem, and relatively convincing overdriven trem via the Saturation control—each modulating in tap-tempo or manual sync with the music. The multiple waveforms offered subtle, but noticeable differences in texture, and being able to switch between them in real-time using an expression pedal allowed for some very nice transitions from one section of a song to another. Used with a single amp, the pedal still sounded great, only less majestic. The Ultrem may be overkill for your needs, but it could well be the last tremolo unit you’ll ever buy.