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Authentic rotating speaker sound and SansAmp overdrive in a stompbox

$295.00 MSRP; $219.00 street, www.tech21nyc.com

By Jon Chappell


(Click image to enlarge.)


Since their inception, the electronically modulated sounds of phase shifters, flangers, and choruses have been an irresistible lure to experimental and creative guitarists. But for the discerning among us, the holy grail for a fat, swirling, truly three-dimensional sound has always been the rotary-speaker effect, as exemplified by the famous Leslie organ cabinet and Fender Vibratone amp. Since these are whole systems requiring moving parts, amplifiers, and special and multiple speakers, it’s been a particularly devilish effect to capture in a portable, electronic-only box. So rather than put up with unconvincing, uni-dimensional, or otherwise poor substitutes, many players seeking an authentic sound have just simply opted for the genuine article. Jimi Hendrix, Eric Clapton, Joe Walsh, Lonnie Mack, Pink Floyd’s David Gilmour, Jethro Tull’s Ian Anderson, Stevie Ray Vaughan, and many others have used the Leslie to classic effect.


While this might be the best solution from a sonic perspective, it has practical challenges. A real Leslie is noisy, hard to find, expensive, and cumbersome to handle. It doesn’t travel well, either, especially if your idea of “traveling with effects” means throwing them in a gym bag or backpack and heading off to the gig. So if a real Leslie isn’t in the cards, what’s a guitar-playing rotating-speaker buff to do?


Enter Tech 21, makers of the classic SansAmp and other effects. In their new Roto Choir, the company has produced a simple-to-use single-stomp effect that perfectly captures the rotary speaker sound in all its complex, swirling, 3D glory. And because rotary speaker effects of yore were almost always tube-driven and inextricable from the resultant sound, Tech 21 also incorporates its own SansAmp technology—unmatched for realistic tube-style distortion and the classic ideal of overdriven guitar sound.



The original, physical rotating speaker cabinet, as exemplified by the Leslie, consisted of two speakers: a woofer for low frequencies (placed at the bottom of the cab), and a horn for high frequencies (at the top). Each speaker faced into a rotor—a reflective baffle with sloped sides—which revolved 360 degrees, independently, at user-controlled speeds. Standing in the vicinity of a Leslie allowed you to hear sound in changing physical phase relationships, based on the changing distances, rate of movement, and the unique interaction of the rotor-modulated speaker output. The Roto Choir captures the essence of these mechanical operations and complements the “moving” part of the sound with an arsenal of analog tone-shaping controls. Working the Roto Choir is simple and intuitive, despite the complex circular calculations at play.



The Roto Choir features six knobs arranged comfortably on two rows. The four top-row knobs (Level, High, Low, and Drive) constitute the bank of all-analog tone-shaping controls (along with the Speaker Sim, described below), and operate as you would expect: Level controls the overall output of the signal; High and Low are for EQ; and Drive dials in tube-like grit and overdrive. Since the guitarists who created classic Leslie sounds almost never used it (or other rotating speaker effects) without a fair amount of overdrive, it’s only natural that the Roto Choir include a Drive control.


Beyond their intuitive operations, though, there is some sophisticated subtlety here. For example, instead of being simple passive filters, as your guitar tone knobs are, the High and Low controls are active, providing boost as well as cut for their respective frequency bands. You can use the High and Low to color any aspect of the signal—accenting or attenuating the edge in the Drive (gain-based distortion), bringing the top horn into sharper focus, or balancing the low and high rotors to each other.




The Roto Choir’s Drive control works in an interesting way, too: for the first half of its travel, it boosts volume as well as preamp-strength. Once past the 12:00 position, the character of the distortion changes in greater proportion to any added gain. This means that you have creative options in the interplay between the Level and Drive controls, and you’re not just limited to loudness and dirt on two unrelated knobs. Nice.


On the bottom row are two knobs devoted to the specific aspects of the rotating speaker effect, and the Roto Choir implements them also in clever ways. The Position control emulates the relative distance of a microphone to the high-frequency horn. Turn the knob down, and the mic is placed further away, creating a more even blend between the high and low speakers. Turn the knob up, the mic is pushed closer, and you hear the high-frequency horn much more prominently. Turning the Position knob all the way up creates a deep-cut tremolo sound, where the bottom of the cycle has almost no amplitude. This is exactly what happens when you stick your ear right up to the upper slots of a real Leslie! The Top Speed knob varies the rotation rate of the upper rotor in either Fast or Slow mode (selected by a footswitch). Since this is really the most significant sound variable in the Leslie and Vibratone effect, the Roto Choir enables us to exercise precise control over it. The lower speaker, being less critical, has well-chosen pre-determined speeds. (Many Leslie owners typically disconnect the lower rotor anyway.)


Just because we covered the knobs doesn’t mean the Roto Choir is out of tricks yet. A Biamp switch (on/bypass) changes the Roto Choir from single-speaker rotating mode (as in the Leslie 125 and Fender Vibratone) to a dual-speaker one (recalling the Leslie 122 model), where both the top and bottom rotors rotate—at different speeds and in opposite directions. A Speaker Sim circuit, when engaged, allows the unit to be optimally patched into a recording rig or full-range-speaker system—aided by the Roto Choir’s board-friendly low-Z output impedance of 1 kOhm. Additionally, the unit features buffered bypass (preferred by this reviewer to “true bypass”), a mono/stereo out, and it can be powered by a single 9V battery or any DC power supply (with negative tip polarity and a 50mA output).



It takes some time with the unit to understand how the different parameters interact, but that speaks to the Roto Choir’s versatility and sonic depth. Even when you grasp how the parameters dynamically influence one another, you can still discover new and exciting textures for your musical visions. I got instant vintage sounds—from classic to psychedelic—with the controls in their upper ranges, but managed to create subtly moving and thickening effects that were new, unfamiliar, and wholly original. Best of all, the rotary speaker sound, in the Roto Choir’s rendition of it, is as different from a chorus as it is from a flanger and phaser. It’s a new effect, with new uses, and the exploration is ongoing.



What I especially like about the Roto Choir is that it feels like a guitar effect. Its controls are housed in a compact, guitar-stomp format, yet it includes the essentials, both tonal and spatial. Best of all is the integration among the tone, distortion, and the rotary-specific effects. Whether it’s an underwater psychedelic tremolo or a slow-moving undulation, there’s just not a bad setting on the Roto Choir. That’s a good sign that the pedal is well-designed and well-voiced. The fact that we have one of the best-ever distortion technologies on board, the SansAmp, seals the deal. The Roto Choir presents the complete signal-chain solution for the rotary speaker experience in a well-designed, compact pedal that’s equally at home in the studio or on stage.



Jon Chappell\\_HCBio\\_101x101.jpg


Jon Chappell is a guitarist and the Senior Editor of Harmony Central. He has contributed numerous musical pieces to film and TV, including Northern Exposure, Walker, Texas Ranger, All My Children, and the feature film Bleeding Hearts, directed by actor-dancer Gregory Hines. He is the author of The Recording Guitarist: A Guide for Home and Studio (Hal Leonard), Essential Scales & Modes (Backbeat Books), and Build Your Own PC Recording Studio (McGraw-Hill), and has written six books in the popular Dummies series (Wiley Publishing).

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