AFTER FOUR GAIN - RELATED stompboxes, Amptweaker has released its next most requested pedal—a modulation effect. The cleverly named SwirlPool ($299) offers tremolo and vibrato in a sturdy box about twice the size of a Tube Screamer, with the signature Amptweaker roll bar protecting the knobs. The SwirlPool’s trem and vibrato effects are not totally separate; once the tremolo circuit is engaged with the left footswitch, the right footswitch alternates between two discreet, additional vibrato circuits, each with Speed and Depth controls. So rather than operating independently, the trem and vibrato effects are synchronized using one of two speed controls, and are blended using the tremolo and vibrato 2 controls. This vintage-amp-based circuit design requires 18-volts from an appropri- ate adaptor (not included) or two 9-volt bat- teries. A handy Volume knob also lets you compensate for any volume drop when the effects are active.

There are five mini-switches: from left to right the first adjusts the amount of chop for the trem, the second and third alter the tremolo and vibrato LFO relation- ship for variations on the effect, the fourth affects tone and vibe for a deeper overall effect, and the fifth determines whether the pedal “ramps” like a Leslie between Vibe 1 and 2, or jumps straight to the chosen settings. An interior trimpot in the battery area adjusts the length of the ramp time. One switch, also located in the slide-out battery compartment, places the universal effects loop (more on this later) before or after the SwirlPool circuitry, while a second switch disables the Tremolo for Vibe 2, leaving it as just Vibrato.

Plugging a Fernandes S-type into the Swirl- Pool and running it into an Egnater Rebel 30 offered up many warm, distinctive modula- tion sounds. Turning the Depth of Vibe 1 all the way down approached a straight trem- olo sound. Turning off the tremolo in the Vibe 2 section, I could then switch between Trem and Vibe. When both “channels” were set for Vibe, I could not only ramp between speeds, but also gradually change the Vibe amount. For example: I could set Vibe 1 at low depth but fast speed, and 2 at high depth but slow speed, to have the effect get more intense as it slowed down.

A distinctive feature of Amptweaker pedals is their effects loop, which lets you add an external effect into the signal chain as you switch on the Amptweaker effect. SwirlPool offers two loops: a universal one that affects both Vibe settings, and one that works only on the Vibe 2 setting. Adding an Electro- Harmonix Neo Clone in Loop 2 turned Vibe 2’s setting into a modulation festival, and while I found the timbral changes wrought by switches 1 through 4 audible and inter- esting at home or in the studio, their subtle effect often got lost on stage.

SwirlPool’s higher speed levels are not very fast, and as a result there are a number of typical trem and vibrato sounds that are unavailable. But many classic tones are, and SwirlPool is not about “typical.” Between the trem/vibe interaction and the dual effects loops, it offers a wealth of sonic possibilities that are definitely not present on standard tremolo and vibrato pedals. In short, if you are seeking unique modulation sounds the SwirlPool’s waters are worth jumping into.

KUDOS Wide range of lush, unique tremolo and vibrato effects. Effects loops add multiple sonic possibilities.
CONCERNS Higher speeds not very high.
CONTACT amptweaker.com