The EM Poll

BOSS RT-20

Aug 1, 2006 12:00 PM, By Nick Peck

           

Boss’s RT-20 Rotary Sound Processor gives you four -different algorithms and several parameter options for re-creating the sound of a Leslie rotating-speaker cabinet.

The Boss RT-20 Rotary Sound Processor ($299) simulates the sound of the Leslie rotating-speaker cabinet. The Leslie's rich, whirling tremolo is associated primarily with the Hammond organ, and the two have been practically inseparable for more than a half century. But the Leslie cabinet also has been a favorite of guitarists such as Eric Clapton and George Harrison, and the rotating-speaker effect sounds terrific on a variety of other instruments as well as on vocals.

The RT-20 has two footswitches: one to turn the effect on and off, and the other to switch the speaker rotation speed between slow and fast. It has stereo inputs and outputs and also can work in mono.

Whirling Dervish

A Leslie speaker has only two controls: volume and rotation speed. The RT-20 gives you several parameters, allowing you to tailor the effect to your taste. The Mode knob lets you select from four different rotating-speaker algorithms: standard rotary (natural Leslie 122 simulation); enhanced rotary (a 122 with exaggerated tremolo); enhanced rotary with stack-amp overdrive (a 122 with Marshall-stack distortion); and Uni-V with stack-amp overdrive (a Univibe pedal simulation with Marshall-stack distortion).

The RT-20 offers separate knobs to adjust the slow and fast “rotor speeds” to taste. The Balance knob varies the blend of the bass and horn rotors, and the Rise Time knob controls the rate at which the rotors slow down when going from fast to slow speed. The Overdrive knob allows you to add distortion to the signal, and separate Effect and Direct knobs let you adjust both the wet/dry mix and overall level. Finally, there are two nifty additional jacks on the back of the unit: an expression-pedal input for continuous speed control and a headphone output.

Sound Spin

I've always loved the sound of a Rhodes through a Leslie, and so I plugged my Rhodes into the RT-20, which fed a 1965 Fender Bassman. The standard rotary mode added a nice animation to the bell-like sound of the Rhodes, and adjusting the direct and effect levels allowed me to dial in the sweet spot quickly. Pushing the balance toward the horn rotor a bit emphasized the brightness of the Rhodes nicely. The RT-20's overdrive sounded a bit harsh and edgy to me — not as satisfying as the naturally warm growl of the Bassman's real tube distortion.

I then tried a variety of Hammond organ patches from a Proteus 2000 with the RT-20. The effect livened up the sounds, adding a depth and vibrancy to the normally frozen, static quality of the samples. As a gigging keyboard player who uses Hammond sounds as a color in his palette rather than as his primary focus, I could see the RT-20 being a handy Leslie replacement. However, organ aficionados who work with real Leslie speaker cabinets might consider the RT-20 an homage to the real thing rather than an exact replica.

Jazz guitarist Pete Fogle takes a traditional, minimalist approach to his tone, favoring a Gibson electric hollowbody, a Crybaby Wah, and a Fender Deluxe Reverb. He took the RT-20 for a spin and loved it. In a guitar context, the slow rotor-speed sound felt reminiscent of a '60s-era phase shifter, and the fast speed created a wobbly tremolo with a psychedelic edge that favored the guitar well. The overdrive, which I didn't care for on keyboard sounds, added a crunchy edge that felt right at home with the guitar.

The RT-20 has some design drawbacks. Rotation speed is displayed by a large, fancy multisegment LED display that reminded me of a disco-era dance floor. A single pulsing LED would be less distracting and would require less power. Speaking of power, the unit requires six AA batteries rather than the single 9V battery found in most pedals. Alkaline batteries are estimated to last 12 hours in this unit, so the optional power adapter is really essential.

Starting Rotation

In terms of Leslie emulation, Boss has made a solid, worthy contender with the RT-20. While the overdrive sounded a bit edgy to my ears, and the virtual rotor display seems gaudy and unnecessary, I was able to coax a lot of pleasing sounds out of this box. The natural Leslie simulation, while not a perfect duplicate of the real thing, was enjoyable to listen to on a variety of instruments and really shone on electric guitar. I liked the variety of parameter controls and the build quality of the unit. If you are looking for a Leslie sound but don't want to carry around a 150-pound cabinet, then you, too, should take the RT-20 for a spin.

Value (1 through 5): 4
Boss
www.bossus.com