Optical Tremolo: Extended Play

From Charles Platt’s “Hypothetical Tremolo Wheel” (MAKE Volume 15, page 82, “Stomp Box Basics: Tremolo and Fuzz”) to real-world project box, MAKE Technical Editor Sean Michael Ragan walks through building out this circuit in MAKE’s latest issue (Volume 33, page 96).

With this Optical Tremolo Box you are hearing are patterns of light, created by a spinning disk translated into rapid electrical fluctuations to produce a warbling audio effect. Audio enters the circuit via the input jack, passes through the variable resistor — the light-sensitive photocell — and outputs to the amplifier, creating the effect known as tremolo.

Tremolo itself can be found in many instruments, and includes most types of drum rolls, some singing techniques, “bends above the nut” on a guitar, or tuned and de-tuned ranks of pipes of an organ. It can also be produced with synthesizers. As a classical guitar technique, tremelo is perhaps best known by Francisco Tárrega’s Recuerdos de la Alhambra.

MAKE Volume 33 features our special Software for Makers section covering apps for circuit board design, 3D design and printing, microcontrollers, and programming for kids. Also, meet our new Arduino-powered Rovera robot and get started with Raspberry Pi. As usual, you’ll also find fascinating makers inside, like the maniacs on our cover, the hackers behind the popular Power Racing Series events at Maker Faire.

Try your hand at 22 great DIY projects, like the Optical Tremolo guitar effects box, "Panjolele" cake-pan ukelele, Wii Nunchuk Mouse, CNC joinery tricks, treat-dispensing cat scratching post, laser-cut flexing wooden books, sake brewing, growing incredibly hot “ghost chili” peppers, and much more.

On newsstands now, by subscription, or available in the Maker Shed

Buy now!

4 Responses to Optical Tremolo: Extended Play

chuck on January 31st, 2013 at 11:36 pm said:

Here’s an update on my latest optical tremolo project-
I’ve been working with sequenced synths using 40106, 555, and 4017 chips. I’m getting cool sounds but it gets a bit repetitive. I wanted to design something that would slowly change parameters like rate, pitch, FM mod, LFO rate etc. I built a similar optical device but instead of a fast motor I used a quartz clock movement and I used a disc made from a piece of x-ray film over the shaft for the minute hand so the disc turns once an hour. I built the whole thing in a light fast box so the LED would be the only source of light. Instead of using the photo resistor as a through switch I used it as a variable resistor to control the rate of a sequencer. What I got was a sequence that slowed down and sped up very gradually depending on the light or dark areas of the x-ray as the clock turned. I built a second unit to control the frequency modulation of the synth. This works great to take a simple sequenced loop and turn it into something more complex and interesting. Now I want to add some kind of speed adjustment to the clock motors.
Your optical tremolo is turning out to be far more versatile than I initially thought. Thanks for the seeds!

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- Nick Normal on February 4th, 2013 at 9:05 am said:
  
  Chuck! Thanks so much for the report back on your continued builds and progress. This sounds like a fantastic project. I’m trying to imagine all the parts and pieces working, and look forward to some pictures if you have a blog or post them anywhere, let me know. What originally inspired you to use x-ray film?
  
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  chuck on February 4th, 2013 at 2:13 pm said:
  
  I have decided that it is indeed time to start a blog so I’ll let you know when I have something up. I’ll get some new video up soon too, I just can’t stop doing stuff long enough to document it!
  I use x-ray film to make stencils so there are always scraps laying around the shop. It’s a great material to work with.
  
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