TWA Triskelion

The TWA Triskelion is a midrange filter and gain booster built around the circuit of the rare 1970s Systech Harmonic Energizer. TWA describes the current Mk. III as "essentially a parametric midrange filter with adjustable peak and an obscene amount of gain," with an extended high-frequency range and expression control over the filter sweep¹. In practice it behaves like a cocked wah pedal with an adjustable peak and a lot of gain, letting you push a narrow band of mids for solos, dial in glassy clean tones, or tune your rig to a room for resonant feedback².

The Triskelion circuit is based on the uber-rare Systech Harmonic Energizer, a filter and distortion box from the '70s used by players including Frank Zappa, Greg Lake and Joe Walsh²³. TWA says it was the first company to offer a production re-production of the original, and the maker voiced the pedal from an actual vintage Systech unit³⁴.

What it does to your sound

The Triskelion is a bandpass filter, which means it emphasizes one band of frequencies rather than cutting or boosting across the whole spectrum like a graphic EQ. Delicious Audio describes it as "acting as a cocked wah pedal with an adjustable peak and a ton of gain, pushing different frequencies like a parametric mic EQ with adjustable Q"³. Set the frequency low and back off the gain for a thick, throaty solo voice; set it higher for glassy clean textures; or crank the gain and let the filter ring to tune your rig to the room for singing, resonant feedback².

GuitarPlayer's Art Thompson tested the Mk. III through amps from a Fender Deluxe Reverb to a Mesa/Boogie Mark 5:25 with both single-coils and humbuckers, and found it useful in front of a Fulltone OCD set to a moderate drive level for controlled feedback and infinite sustain at the touch of a button⁴.

Controls and jacks

The Mk. III keeps the control set small. The names come from the original Systech, and they map to familiar functions:

The jacks on the Mk. III cover input and output, a 1/8-inch FSW jack for remote on/off control of the Amplitude function, and a 1/8-inch EXP jack for an expression pedal⁴. GuitarPlayer notes the EXP jack lets you manipulate the Variant Mass in real time⁴.

Power and bypass

The Mk. III runs on a 9V battery or external 9 VDC power with low current draw². The Mk. II, by contrast, required external 9 VDC with no battery option⁹. Bypass is TWA's proprietary S3 "Shortest Send Switching," a relay-based true bypass that defaults to bypass if power is lost, so a dead supply leaves your dry signal intact⁸. GuitarPlayer's review describes the same S3 relay and mechanical true-bypass switching on the Mk. III⁴.

Expression control and the Side Step

The expression input is where the Triskelion goes beyond a fixed EQ. An expression pedal connected to the EXP jack controls the frequency sweep of the filter, so you can wah the midrange band by hand or foot¹. It also accepts the TWA Side Step, which turns the Triskelion into a tap-tempo LFO modulator¹. With the Side Step in the chain you get three modes: manual control of the midrange frequency via expression pedal, LFO control of the frequency via the Side Step, or a fixed midrange frequency with the Triskelion on and the Side Step bypassed⁶.

Mk. I, Mk. II and Mk. III

The Triskelion debuted at Winter NAMM in 2010 as the TK-01, eliciting, in the maker's words, "hushed whispers, envious glances, and more than a little head-scratching"¹⁸. The original operated more or less as a standard EQ boost and distortion pedal, with an Amplitude knob driving the distortion circuit, an Engage button that bypassed the distortion so the EQ could be used alone, and a Boost button that added subtle octave harmonics for a more shimmery tone¹⁰. It also had an insert jack for an expression pedal for extreme wah-wah effects¹⁰.

The Mk. II followed in 2015 in a smaller, pedalboard-friendly package with features based on user suggestions¹. Its additions included an internal Gain DIP switch that reduced gain for headroom, an internal Classic/Modern DIP switch selecting between two filter frequency ranges, an HP switch for extended frequency range, and a Gain Select switch choosing between the original or an attenuated gain level⁸¹¹. It required external 9 VDC power with no battery option⁹.

The Mk. III, new for 2021, combines features of all previous versions in a smaller, pedalboard-friendly chassis². TWA's engineer redesigned the filter section of the circuit, reducing the noise level so it plays better with other dirt devices, and the pro-audio quality noise floor of the Mk. II carries over³. The Variant Mass Boost switch of the original Triskelion returns, adding an ear-shattering upper range to the filter, and the Mk. III adds the extended high-frequency range and expression control over the sweep¹. Guitar Pedal X's review notes the VM Shift elevates the center frequency by an octave⁵.

Who uses it

The player most associated with the Triskelion is Dweezil Zappa, who relies on it to replicate his father Frank's guitar sounds for the Zappa Plays Zappa project and has been known to run as many as three in his live touring rig⁸¹¹. Guitar World filmed him demonstrating how he uses the pedal to replicate some of Frank Zappa's tones, noting it also produces tones similar to the vintage Maestro Parametric Filter¹². Premier Guitar's launch coverage also lists Lyle Workman and Megadeth's Dave Mustaine among well-known users².

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