Mechanical Tremolo Does Things The Old-School Way

The word “tremolo” has a wide variety of meanings in the musical lexicon. A tremolo effect, in the guitar community at least, refers to a periodic variation in amplitude. This is often achieved with solid state electronics, but also recalls the sounds created by Hammond organs of years past with their rotating Leslie speakers. [HackaweekTV] decided to do things the old fashioned way, building a mechanical tremolo effect of his own (Youtube link, embedded below).

Electronically, the signal is simply passed through a linear audio potentiometer. The effect is generated by rapidly cycling this potentiometer up and down. The motion is achieved through a geared motor salvaged from a Roomba, which turns a cam. A sprung follower sits on top of the cam, and is attached to the potentiometer.

There were some challenges in development. Rigidity of the frame was an issue, and the follower had issues with snagging on the cam. However, with some careful iteration they were able to get everything up and running. The final project sounds great, and with the amplifier turned up, there’s no need to worry about the sound of the moving parts.

Naturally, you can always build a tremolo with a 555 instead. Video after the break.

21 thoughts on “Mechanical Tremolo Does Things The Old-School Way

  1. or do things the black metal way and just play really really fast. i like how some of them can do a four string chord on the up and down stroke 32 times a bar. though this kind of playing requires superhuman abilities and a pact with satan.

  2. TL/DW but from that last few seconds it sounds good and looks cool, shame he blew the motor though, maybe a bigger one next time, and if I could play a guitar I’d buy one.

    1. I’m curious. How much time is “too long”? How long should my videos be in order to accommodate your attention span. I genuinely want to know. Give me a number. 15 maybe even , OMG, 45 seconds? :)

    1. I get why he did it that way, but I would have used a large diameter wheel, and connecting rod with a setscrew in a movable radius on the wheel- kind of an adjustable train wheel linkage arrangement, adjustable stroke.

      Benefit of both simplicity, and noiseless/frictionless if made carefully with good bearing motor. Simpler to make too, but can’t be adjusted while running easily.

  3. Hammond actually did this with palladium contacts and a resistor ladder on their oldest organs. Laurens didn’t want Leslie’s stuff on his organs in the early years. The eccentric was geared down and driven by the main motor in the generator. The “gas” pedal was a sliding ramp and a similar stack of precious metal contacts with a resistor ladder. Then they went contactless with capacitance for FM vibrato instead of AM tremolo in the famous scanner and the volume pedal was also a variable cap like an AM radio tuner, no noise at all.

    Not a 555 but a phase shift oscillator (sine wave) and neon lamp (one tube of course) coupled to a photo resistor. Choppy sound is bad, the photo trick perfectly biases the desired amount from a little to max modulation without cutoff.

  4. I remember some setup with a lamp, ldr and a sprocket wheel. No movable parts carrying the signal, so no wear on the potentiometer. Its how swell pedals from electronic organs work on the more expensive machines work

  5. A custom round pot that goes all the way around, with its 2 fixed terminals placed 180° from each other, would give you the effect just by rotating continuously.

    Or if you wanted to get really weird, cover a dekatron with a circular gradient from clear to black to clear again printed on transparency paper, then place a big photoresistor in front of it.

      1. You seem rather hostile toward anyone who comments negatively. Don’t let it bother you. It’s the internet. People will comment negatively even if your video was the best thing in it’s class. When somebody criticizes one of my blog posts or videos, I usually end up just agreeing with them about how awful it was LOL.

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