I first heard a Hammond organ with a Leslie via Booker T. & the M.G.'s on The Blues Brothers movie soundtrack in 1980. I think I saw that movie over a hundred times as a kid, and I memorized the dialog and could play the songs and guitar licks. The tone, groove, and melody in "Time Is Tight," with Booker's organ and Steve Cropper's guitar locking and trading, hit a nerve in me. I still consider it the best soul instrumental ever.
"I first heard a Hammond organ with a Leslie via Booker T. & the M.G.'s on The Blues Brothers movie soundtrack in 1980."
So, let me explain how this swirling sonic effect works and share how to get great tone out of Fender's rotating pseudo-Leslie. The patent for "continuous modulation by acousto-mechanical means, e.g. rotating speakers or sound deflectors" was filed in 1956 by Donald J. Leslie. Since CBS owned both Fender and Leslie in the mid-'60s, they crossed brands and introduced the Vibratone for guitarists in 1967, based on the Leslie 16. The Vibratone was equipped with a single 10", 4-ohm Jensen speaker and required an external driver amp. In front of the vertical speaker, there is a rotating, circular Styrofoam rotor, with an asymmetrical opening. As an internal motor spins the rotor, the sound waves are intermittently blocked and allowed to pass through its opening, which creates a 3D Doppler effect. The audible result is that the frequency and volume are changed as the sound exits the cabinet at three places—both sides and the top—which simultaneously creates both tremolo and vibrato effects. The rotor has two speeds: approximately 40 and 340 rotations per minute.
Jimi Hendrix, David Gilmour, and Robin Trower are among the notable guitar-wielding, classic-rock proponents of the Leslie effect. Here, the author drives his Vibratone with a Bandmaster Reverb head.
Since the Vibratone speaker sits deep into the cabinet, it sounds muddy, bass-y, and not as loud as a regular cab. Swapping with a louder 12" speaker is recommended, so the Vibratone can keep up with other amps onstage. Speakers with neodymium magnets can reduce weight in the 77-pound cab. I like to use powerful 40-watt driver amps with wide EQ possibilities to get enough cut and clean volume with the Vibratone. Also, I prefer to not plug in via the cabinet's crossover coupling unit with its high-pass filter. Instead, I install an input jack on the back, simply wired directly to the speaker. Keeping things simple reduces sources of failure, and the amp's crossover introduces unnecessary complexity. Without that mod, I simply dial down the bass on the amp.
Black-panel Bandmaster, Bandmaster Reverb, and Bassman amps are great drivers for the Vibratone since they are powerful, 4-ohm rated, and have enough sparkle. Plus, they sit nicely on top of the Vibratone. I use a second combo amp—for example, a Super Reverb—with the dedicated amp driving the Vibratone. An AB/Y pedal lets me select the Vibratone alone, the Super Reverb alone, or both together. I use two microphones on the Vibratone—one on each side. They are panned oppositely in the PA, with the left microphone panned 80 percent to the left and the right panned 80 percent to the right. This creates a big swirl in the room, and the audience can hear the powerful rotating vibrato effect in stereo through the PA. You don't get this kind of full stereo vibrato in a room with a single amp and a chorus pedal.
Note the sound ports on the top and sides of the cabinet, which, along with the rotor, give the Vibratone its Doppler effect.
The only other amp vibrato effect to challenge the sound of the Vibratone appeared in Magnatone combos of the same era and continues to be part of the recently revived brand's recipe. Magnatone's frequency modulation happens in the electrical circuit, using tube gain stages with varistors, which are resistors that simply drop in resistance value as the voltage across them increases. This circuit-based vibrato is more electrically advanced, requiring more components and more tube and overall circuit maintenance. But the upside is that you can get stereo vibrato out of small and lightweight combos without lugging around a bulky speaker cabinet with its electrical motor, belt, and a rotor that requires oiling and other maintenance.
There are several modern rotating speakers that are easier to find and maintain than a vintage Vibratone or Leslie. I've also found a few good Leslie-effect pedals, like the Analog Man chorus. But they don't beat a mechanically rotating Leslie-designed Vibratone in stereo mode, IMHO. Now, I hope you are inspired to go find your swirl.
The Bandmaster Reverb head was built from 1968 to 1980 and has enough grille-room to install a pair of 8" speakers—a popular mod.
Fender introduced their piggyback amps in the blonde era, in 1960. Before that, during the tweed era, there were only combo amps. The piggybacks were designed to be loud, clean, and have lots of punchy bass from closed cabinets with 12" or 15" speakers. Most have solid-state rectifiers with no sag, and either two or four 6L6GC power tubes producing typically between 50 and 85 watts. They have massive power and output transformers, keeping things firm at high volumes and compatible for use with bass guitars. An exception to all the above is the smaller Tremolux amp, which we'll come back to.
A higher speaker impedance reduces the clean headroom, which is sometimes useful.
An advantage of using separate speaker cabinets is the flexibility to vary tone and volume by pairing amps to the cabinets they were designed for or to any other cabinet, as long as you stay within the safe impedance range: between -50 percent and +100 percent of the amp's rating. There is a huge difference in tone and volume playing a 4-ohm Bandmaster through a small and light cabinet with a modest, vintage-style 10" speaker at 8 ohms versus a closed-back 4x12 at 8 ohms with loud Celestion speakers. Or you may use a bass guitar with a single 15" bass-style cabinet. I encourage you to experiment and learn how to pick the right pairing for the right job. A rule of thumb is to match the amp and cabinet impedance, for the most possible wattage and volume. A higher speaker impedance reduces the clean headroom, which is sometimes useful.
Now, let's discuss the black-panel Tremolux—the only small piggyback amp. It has a normal channel, a vibrato channel, a GZ34 tube rectifier, two 6L6GCs, and lighter transformers, and was originally designed for a 2x10 closed-speaker cabinet. This amp produces a modest 35 watts and breaks up much earlier than its bigger brothers. It is sought by Fender players looking for natural tube distortion.
The Tremolux—a tiny, low-powered titan of the Fender head family—is sought by players desiring more tube-driven breakup.
Moving up the scale, the black-panel Bassman and Bandmaster amps may look similar, but their innards are not. Both are dual-channel amps powered by 6L6GC tubes and diode rectifiers, built for driving 2x12 speaker cabinets. The main differences are that the Bandmaster has tremolo and a smaller, 40-watt-output 125A6A transformer (same as the Vibrolux Reverb). The AB763-circuit Bandmaster's two channels—"Vibrato" and "Normal"—have similar preamp circuits and sound alike. The main difference is that the Bandmaster has tremolo. The circuit design and tone stacks relate very much to the Deluxe, Vibrolux, Super, and Pro combos, with typical sparkling, clean, and scooped black-panel sound.
The black-panel Bassman AB165 is different than other black-panel amps. At low volumes, black-panel Fenders sound clean, but when turned up, the Bassman distorts more because of an extra preamp-tube stage. Its tone is also slightly bigger and firmer than the Bandmaster, because of its larger output transformer. The Bassman's "Bass" channel is voiced for bass guitar, with a deep switch, while the normal channel is voiced for guitar, but without vibrato. I find the black-panel and silver-panel 50-watt Bassman to be a great bass amp, with articulate and strong lower mids that fit well in a band context.
Both the Bandmaster and Bassman continued in the silver-panel era, but with changes. The Bassman's power was first increased to 100 watts with four 6L6GC power tubes. A 70-watt version became available in the late '70s. In 1968, the Bandmaster Reverb was introduced, with a 5U4GB rectifier tube and a smaller 125A6A output transformer (same as the Vibrolux Reverb), both resulting in more sag and reduced clean headroom. The cabinet height grew a few inches to fit the reverb tank. The 4-ohm Bandmaster Reverb is one great, versatile tone platform with reverb, vibrato, and rich EQ possibilities, useful with all kinds of guitars, pedals, and speaker cabinets. If you own a silver-panel Bandmaster Reverb, you might consider getting an amp tech to revert the bias circuit back to black-panel specs, for better bias control.
Finally, the most powerful black-panel piggyback amps are the Showman and Dual Showman, with four 6L6GCs producing 85 watts. They came with single or dual 15" JBL speakers and large output transformers wanting 8- or 4-ohm loads, respectively. Be aware that some Dual Showman amps actually have a 4-ohm output transformer, and sometimes the faceplate says only "Showman." It's also worth echoing that Fender added reverb to the silver-panel version, to create the Dual Showman Reverb. And now, you know the basics of Fender's piggyback gems.