GUYATONE Ultron and Ultrem

Are these boutique stompboxes the ultimate in their class?
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Autowah effects like the Musitronics Mu-Tron III have been around since the '70s. Stevie Wonder's “Higher Ground” and other funk classics made them popular, but I've never felt they were exploited to their full expressive potential. I've always wanted more far-reaching control over their resonant filters.

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FIG. 1: Guyatone''s Optical Series stompboxes have plenty of knobs and switches, multiple modes of operation, and customizable control options. The Ultron filter pedal offers autowah, envelope-controlled, and footpedal-controlled modes.

The pulsating swell of tremolo is another perennial favorite. Though tremolo has been used (and occasionally overused) on everything from twangy surf guitar to panning electric piano, its simplicity and potential for monotony have made it practically cliché. Thus, I was excited to try out the Guyatone Ultron and Ultrem stompboxes, which aim to push the limits of autowah and tremolo to their outermost reaches.

Uncommon Features in Common

The Ultron Optical Auto Wah GST-U05 and Ultrem Optical Tremolo GST-C04 are hybrid analog-digital stompboxes. They combine vintage-inspired optical circuitry with a digital low-frequency oscillator (LFO) and a control section that lets you manipulate lots of parameters in real time. Each unit is housed in a sturdy but lightweight Hammond chassis and is dedicated to one effects type. Each sports a full complement of LEDs, switches, and knobs, many performing dual functions, and a 4-character LED display (see Fig. 1). Their range of tweakable parameters is so extensive, they're almost mini sound-design workstations in stompbox form. I divided my time between stompbox operation and tabletop tweaking because I couldn't keep my hands off of all the controls.

I was delighted that each unit comes with an external power supply (a 9 VDC wall wart), but when I opened the box, I was a little dismayed to find no place to install a battery. Guyatone discovered during development that the digital CPU's power demands made battery operation impractical. Still, it would be nice to have at least a power switch, as unplugging the wall wart is the only way to turn the unit off. However, while poking around inside, I found a vastly more valuable feature: four DIP switches and a threshold trim pot you can use to optimize the units for different instruments, including keyboards. Nice!

Both stompboxes offer six LFO waveforms (triangle, sawtooth, reverse sawtooth, and three rectangular waves), LFO speed (displayed in bpm or milliseconds and as a bright green LED that flashes in time), a true bypass switch, and an input for an optional CV expression pedal (Guyatone recommends a Roland EV-5). You can manually dial in the LFO rate or set it using tap-tempo foot control. The tap-tempo footswitch also doubles as a switch for controlling various operational modes. The Ultron's and Ultrem's modes, many of which require expression pedal control, are really the key to unlocking the power of these devices.

Ultron Optical Auto Wah

Calling the Ultron GST-U05 an autowah is somewhat of a misnomer, because one of the features setting it apart from earlier units (like the Mu-Tron III) is that you can control the filter manually with an expression pedal. Each of the Ultron's three basic modes offers a different way to control the filter. Controlling it with an expression pedal is called Manual Pedal Wah mode, and it works like a traditional wah-wah pedal. Touch Wah controls the filter using pick attack or some other input signal, and Wave Wah controls it using the internal LFO.

Touch Wah (envelope-controlled) mode essentially nails the Mu-Tron III effect, but with even more user options. Control knobs include Peak (filter resonance), Frequency (filter cutoff), Threshold (envelope sensitivity), and Filter Mode (highpass, bandpass, lowpass, or notch). Toggle switches let you select the filter range (low, medium, or high), and filter cycle up (wah-wah) or down (ow-ow).

Wave Wah (autowah) mode places the filter under LFO control for a distinctly different wah effect. You can further customize the effects using the various controls, the six selectable waveforms, and manual or tap-tempo speed controls.

Manual Pedal Wah mode is one of my favorite options. It gives the player ultimate control, serving up super liquid-cooled extreme wah-wah filter tones that will leave envious shred-meister guitar rivals looking like crybabies (see Web Clip 1).

Even when you have selected one of the Ultron's three basic modes, you are not locked into it as a static choice. You have the ability to momentarily switch to another mode (Guyatone calls it a sub mode) using the footswitch labeled Control. For example, when in Touch Wah mode, pressing the Control switch takes you into Wave Wah mode. That allows you to do things like have autowah on choppy chords and then suddenly invoke a pulsating wah on a sustained chord.

In addition to filter frequency, you can use the expression pedal to control the LFO's depth and speed. In any of the available pedal modes, you can use the Control footswitch to momentarily switch to envelope-controlled wah on the fly. As if all that wasn't enough, you also get two bonus modes that let you change LFO waveforms with the expression pedal.

Ultrem Optical Tremolo

Tremolo is a less flashy effect than autowah, and that's reflected in the Ultrem GST-C04's lower price. But the same deluxe treatment is evident in its design, which packs in as many features and control options as possible for a full variety of tremolo and volume effects, and more (see Fig. 2). The six selectable LFO waveforms cover everything from spot-on emulations of vintage tremolo tones to more modern and mechanical-sounding autogating effects. The Ultrem has stereo outputs for panning tremolo, and you can use an expression pedal to manually pan between amps or channels. You can also use an expression pedal to control volume as well as tremolo speed, depth, and waveform.

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FIG. 2: The Ultrem offers a deluxe set of tremolo and volume effects paired with simulated tube saturation.

Like the Ultron, the Ultrem has three basic modes. Wave Tap lets you change tremolo speed on the fly using the tap-tempo footswitch. Momentary Wave mode allows you to toggle the tremolo on and off using the Control footswitch. And in Pedal Volume mode, the expression pedal functions as a standard volume pedal.

As with the Ultron, you can mix and match all the Ultrem's options in real time. It gives you countless variations using the Control footswitch and the same main mode and sub mode scheme. The Control switch also lets you control tap tempo, which in itself is a rare feature for a tremolo unit. One of my favorite Ultrem features is the Blend option, which mixes in a bit of dry signal to ensure that the initial note attack is not lost in a volume swell. In addition, the Ultrem offers a Saturation effect that allows you to dial in varying degrees of tube-overdrive emulation. It's a subtler tube crunch than a full-blown sustain or distortion effect. The effect is warm, pleasant, and musically useful; in fact, it's one of the best tube-saturation effects I've heard.

Ultimately …

I've owned quite a few stompboxes over the years, and it takes a lot to get my attention, but the Ultron and Ultrem immediately impressed me. I instantly became engrossed in exploring their extraordinarily flexible performance options, and even after weeks of putting them through their paces, I've yet to come up for air. It is rare to find a device for which the answer to the question “Okay, but can it do this?” is most likely, “Yes, and several other tricks you hadn't even imagined.”

Both units also impressed me with their solid construction and pristine audio quality with nary a hint of noise. And even with so many knobs, switches, dual modes, dual-function controls, and tweakable parameters, I found the user interface to be quite ergonomic, requiring only minimal skimming of the manual for most functions.

The Ultron and Ultrem do carry boutique price tags, and cheaper stompboxes offering similar effects are certainly available. An expression pedal is a must, so if you don't happen to have an EV-5 pedal around (as I did), that would be an additional expense. Although other devices may do some of what these two stompboxes can do, I have yet to see anything else that brings together so many control options and features. Moreover, the ability to adjust input threshold to accommodate line-level sources makes them suitable for sound design, project studio recording, and a variety of audio processing needs, in addition to guitar and bass applications. Using both effects together, along with a little creativity, you can generate a wide range of electronic effects, taking a guitar (or other signal) through some pretty exotic timbral territory (see Web Clip 2).

Are the Ultron and Ultrem the ultimate autowah and tremolo stompboxes? I do wish for a power switch, though I suppose it would be unusual for a stompbox to have one. I also wish that adjusting the input gain didn't require opening the unit and messing with DIP switches. Those are relatively minor quibbles, though. The combination of exceptional real-time control flexibility, top-quality audio components, ergonomic design, and adjustable input level makes these devices if not the ultimate, then pretty darn close.

Babz is a composer, multi-instrumentalist, and music-technology writer in New York City.


Ultron and Ultrem

effects stompboxes
Ultron $425
Ultrem $375



PROS: Deluxe feature set. Exceptional versatility. Real-time control flexibility. Excellent sound quality. Solid construction. Quiet operation.

CONS: No battery operation. No power switch. Expensive.