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November 2023
Vol. 23, No. 2

Zen of Recording

Find It First, Then Plug It In and Rotate

by Sven-Erik SeaholmSeptember 2014

What’s that spinning voodoo I hear? Is that whirling, swirling sound the tidy bowl man’s last hurrah? Perhaps my stomach is informing my brain that two tequilas is way more than sufficient. Nay, not so. It’s the beautiful opening strains of Procol Harem’s “Whiter Shade of Pale.” More specifically, it is the exquisite sound of a Hammond B3 organ running through a Leslie® rotary cabinet. A combination that was always as cumbersome to lift as purchase, until Hughes & Kettner, those German ambassadors of tone that brought us the venerable Red Box DI/amp simulator and tons of amps, etc. gave us one more export to be thankful for besides beer, bratwurst, and Falco: the Tube Rotosphere rotary cabinet emulator.

An original rotary cabinet (or Leslie®) is a large box-like structure that houses a rotating tweeter in the upper section and a rotating woofer in the bottom section. The speakers rotate at different speeds and in opposite directions, creating a blend of Doppler effects, phase shifting, and room reflections that define the characteristic Leslie® sound. An additional contributor to this classic tone is tube distortion, which adds a warm, gritty growl that brings a particularly unique character and presence to the mix. As you might imagine, cramming  all of these features and more into a four-pound box is quite the tall order, but one that the Tube Rotosphere is more than capable of fulfilling.

Upon first glance, the Rotosphere is certainly a handsome little devil. A silver metal housing with black knobs and foot strips, plus a cool little window where you can see the 12 AX 7A tube glowing cheerfully back at you. There are three footswitches along the bottom: “Bypass,” “Breaker,” and “Slow-Fast.” The “Slow-Fast” switch controls which of the two speeds at which the “speakers” spin and the current speed is indicated by a flashing LED. A corresponding bypass led lets you know when the effect is engaged. However,  it’s the “Breaker” switch that holds the key to the Rotosphere’s usefulness and accuracy at duplicating its hefty brethren. An actual Leslie® has a breaker that cuts electric current to the rotary motor, which causes the speakers to slow down to a full stop. When the breaker is released, the speakers gradually accelerate back to full speed again. The Rotosphere breaker does this very naturally and it is remarkable how much it actually behaves like the real thing.

At the top left, a knob labeled “Drive” controls how hard your incoming signal hits the tube, resulting in a satisfyingly wide range of distorted tones from clean to downright grungy, which is signified by a glowing led to it’s right. An “Output” knob controls the level coming out of the unit and again, a very generous amount of range here as well. At the top right is a knob that adjusts the balance between the “tweeter” and “woofer,” which are also represented by flickering LEDs.

On the back are four quarter-inch jacks that can be used as true stereo in and outs, or you can use the right/mono at either stage if you prefer. A “Mode” switch adjusts the impedance and eq filtering for either keyboard or guitar signals. Another quarter-inch jack allows you to remotely control the “Bypass” and “Slow-Fast” switches. Last and most certainly least is a jack for the obligatory “wall wart” power supply. A piece of advice: buy an extra one. The Hughes & Kettner power supplies seem to have a finite lifespan.

Here’s the crappy part: They discontinued.

Production of the Rotosphere ceased some years ago and they are now somewhat of an Ebay treasure, where they can be found used for between $150-$250. A host of replacement footswitches and other accessories are also plentiful there.

Whether you’re using it with organ and other keyboards, giving your guitar a new attitude or running vocals through it for that Revolver-era Beatles vibe, I know that the Tube Rotosphere will give you the same outstanding results I’ve experienced with it. Take one for a spin and I’ll see you at the “rotary” club!

Sven-Erik Seaholm is a San Diego-based artist/producer who provides recording and mastering services through his company, Kitsch & Sync Production (

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