#WeekendProjects Q&A: Upgraded Optical Tremolo FX Box

Music Technology
#WeekendProjects Q&A: Upgraded Optical Tremolo FX Box


Even having seen photos of the Optical Tremolo 2.0 in pre-production, when I first saw Make executive editor Mike Senese hold up the project in the above video, I couldn’t help but laugh out loud. Not because it’s funny, but because the project build is so solid, so impressive, and that’s just how I’m wired to react.

Make technical editor Sean Ragan is an accomplished builder and maker, and has been a backbone of the Weekend Projects series for years now. I have insights to how he works, and knew elements of the 2.0 build were discussed after the incredibly popular original Optical Tremolo hit the feeds. But I still had a few questions lingering about his upgrade process, so I shot him some questions, and wanted to share his responses with you all.

The takeaway for me is to keep iterating your ideas, and to share them. It may take more time and cost more money, but you often won’t really see the flow and function of your project until you build it at least once. And some of the best modifications will come from you inspiring others, and from them saying or building something you might not have considered the first time around. That’s the freedom of making.

Nick Normal: Looking back at the first version Optical Tremolo, did the build and form factor come to you as soon as you read Charles Platt’s concept in Make: Electronics (“Stomp Box Origins,” p. 261), or did it click later with some other bit of inspiration?

Sean Ragan: The principle of the project — how it might work — is quite clear from Make: Electronics. So development was all “form factor,” really. There was no one big “aha” moment where everything clicked. I did a lot of experimentation and prototyping. My priority was keeping the 1.0 build as simple as possible. It requires almost no soldering and everything is panel-mount — there’s no perfboard or PCB. The circuit wiring is done with a stereo terminal strip. Instead of complicating the schematic by adding a circuit to power the LED and trying to figure out how to build my own gooseneck, I used a complete off-the-shelf pocket LED flashlight with a gooseneck already on it.

But all that came out of a relatively elaborate prototyping process. First I experimented with circuits on breadboards, then I built a cardboard enclosure prototype in an empty Kleenex box so I could test the physical relationship between the light, the sensor, the motor, and the spinning tremolo disk. Then I laid out a detailed panel plan in InkScape and used it to build the first plastic enclosure prototype. I think there were at least two of those before I arrived at the finished version.

Optical Tremolo 2.0’s obvious upgrade is the implementation of the Dial-a-Speed motor controller, replacing the rheostat used in the first build. The Dial-a-Speed is a project unto itself. Was the Dial-a-Speed devised as a solution to upgrade the Optical Tremolo, or built for another purpose and then ported to Optical Tremolo 2.0?

More the former than the latter. Controlling the speed of the motor without over-complicating the build is the main challenge with this project. Designing for DIY is very different than designing for manufacturing. In EE, products designed for an assembly line can get out of control, with the circuit and adding tons of components to get the features just right, whereas when you’re designing a DIY project or kit, every component you add is one more part you’ve got to source and keep track of, and that the builder eventually has to install by hand. So the art is getting the most fun, useful, and interesting build from the simplest possible construction. You want the thing to be desirable as an object, too, because hobby electronics has already suffered enough from builders who don’t pay enough attention to aesthetics.


One of my favorite elements of 2.0 is the drilling out of the CD hub, which then gets mounted on the brushless fan. Was that serendipity or what?

The idea of using an old CD for the tremolo disk, and a CD case hub to mount the disk, came from a reader — Chuck Stephens, of Tampa, Florida — who had been inspired by the original optical tremolo. We did a video hangout with him last year, and he showed off his build including the CD/DVD hub combo. I warned him then I might have to steal it! And once you begin using a CD hub, mounting it on a brushless fan is an obvious improvisation. It does work out pretty neatly all around — you get to use a brushless motor, which has lots of advantages for this build, and you get one for super cheap because those cooling fans are in almost every desktop computer box in the world. Plus it’s so much easier to just stick the flat CD hub to the flat fan hub with double-stick tape than it is to try to figure out how to couple it to a traditional DC motor shaft.

The main benefit of the hub is the use of readymade CDs/DVDs as tremolo discs in place of velcro-backed plastic sweep discs. You mentioned Chuck’s optical tremolo mod. Were you inspired by his build, or were you already planning this sturdy upgrade?

No, that was totally Chuck’s idea. I absolutely do not take credit for it.

Lastly, I know you’ve hinted at a 3.0 version. What are some thoughts there?

The build is already sort of at the limit of complexity for projects as I like to design them. If and when a 3.0 version comes along, I think a lot of the work that I’d put into it would be in simplifying the build process without compromising performance. Then I’d think about improving or adding features.

The one thing that really bugs me about the 2.0 version is that the motor still sometimes needs a manual kickstart at low speeds. At low PWM duty cycles, the fan has enough power to keep spinning, but not always enough to overcome static inertia and start spinning from a dead stop. So you have to give it a nudge with your hand. Once it’s turning, it’s much more stable than the 1.0 version, but you really want it to just start on its own and stabilize at whatever speed it’s set to when you turn the power on. I’d like to experiment with a “kickstart” circuit that gives the fan uninterrupted power at 100 percent duty cycle for a few seconds after power-up to get it spinning, until a capacitor fills up enough to energize a relay or transistor network and switch in the PWM from the Dial-a-Speed. Of course, that’s likely to make the build even more complicated than it already is! It’s always a trade-off. I’ve also thought about using a stepper motor for this build, but they’re pretty loud in my experience, and once you’re doing steppers you’re pretty much committed to digital electronics, which I find much less interesting than analog circuits. Even the 555 in the Dial-a-Speed is pushing it, for me.

I also want to improve the amplifier circuit over the 2.0 build. Right now, the transistor tends to saturate or “clip” — the response you get in the audio from the pattern on the disk tends to be either “all on” or “all off” — and it’s less sensitive to shades of gray than I would like. It should be simple enough to add a degenerative feedback resistor that would improve the middle-range response quite a bit.

And there you have it. As always if you further mod this or any other Weekend Project, find a novel use for tremolo we haven’t previously considered, or even build this project verbatim, we’d like to hear your story. Send us an email with pictures of your build and you could be featured here on the MAKE blog!

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I'm an artist & maker. A lifelong biblioholic, and advocate for all-things geekathon. Home is Long Island City, Queens, which I consider the greatest place on Earth. 5-year former Resident of Flux Factory, co-organizer for World Maker Faire (NYC), and blogger all over the net. Howdy!

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