Organ Donor Gives Up a Leslie Speaker

It was about ten years ago that [Richard] received an old musical organ. Moving to a new house meant it would be cumbersome to move the organ with him, so he opted to harvest some interesting components instead. Specifically, he kept the Leslie speaker.

A Leslie speaker is a special kind of speaker mechanism that creates a tremolo effect as well as a vibrato effect. You can hear this effect in [Richard’s] video below. Simple effects like this would be easy to do on a computer nowadays, but that wasn’t the case several decades ago. Before digital electronics, musical effects were often performed by analog means. [Richard’s] Leslie speaker is a small speaker behind of a Styrofoam baffle. The baffle spins around the speaker which changes the reflection angle of the sound, producing the musical effect.

[Richard] tried hooking this speaker up to other musical instruments but found that turning off the electric motor created an audible pop over the speakers. To remedy this, he build a simple “snubber” circuit. The circuit is just a simple 240 ohm resister and a 0.05 uF capacitor. These components give the transients a path to ground, preventing the pops and clicks when the motor is powered up. Now [Richard] can use this classic piece of audio equipment for newer projects. Continue reading “Organ Donor Gives Up a Leslie Speaker”

Making a better, MIDI controlled Leslie stompbox


Way back before the advent of commercial DSP, musicians had really cool looking gear. One of these devices to change the sound of organs, guitars, and other electronic instruments was a Leslie speaker – a speaker cabinet with rotating horns that gives that wonderful warm warble heard on so many classic recordings. [Nigel] doesn’t have an original Leslie, but he does have a much less expensive and lighter digital effect that emulates the original Leslie sound very well. The only problem, though, is the requirement for a proprietary footswitch. No problem, then, because a transistor, a resistor, and a mint tin can take care of that.

[Nigel]’s Leslie simulator – a Neo Instruments Ventilator – has a foot switch to control the speed of the emulated rotary speakers. There are three possible states for the speakers, fast, slow, and brake, all controlled with a TRS phono connector. Possibly in an attempt to price gouge consumers on a proprietary footswitch, Neo Instruments decided they would use the ring and tip of the phono connector to control the speed. They did so in a way that made it impossible for a single relay or switch to change the speed, however.

No problem for [Nigel], then, because with a very simple circuit consisting of just a transistor and resistor he can use any footswitch he wants with his Leslie simulator. The build doesn’t support the brake function, but he doesn’t use that anyway. Not bad for less than a dollar in parts, and a buck fifty in mint tins.