Well, I finally did it. I built a tap tempo tremolo! It has been a long time coming.
I am going to first show off my build, and then give a little bit of history on the whole line of DIY (and some commercial) tap tempo tremolos, from my perspective.
Tap Tempo Tremolo – Front
Tap Tempo Tremolo – Angle
Tap Tempo Tremolo – Plate
Tap Tempo Tremolo – Plate-detail
Tap Tempo Tremolo – Plate-LEDs
Tap Tempo Tremolo – Plate-switches
Tap Tempo Tremolo – Interior
What I have made is a Tap Tempo Tremolo based around a board I got from Taylor over at MusicPCB.com. It is built into a repurposed Akai Variwah enclosure.
The top middle knob, the toggle switch, and the treadle work together. When the switch is in the Up position, the treadle controls the Speed, and the top middle knob controls the Wave Distort. When the switch is Down, the treadle controls the Wave Distort, and the top middle knob controls the Speed. Of course, you can also tap out a speed with the Tempo switch.
The treadle uses the potentiometer from the Variwah, which is some sort of a custom dual gang pot. It is setup so that it is matched perfectly to the range for the treadle mechanism. Both gangs are linear. When I was testing, I found that the treadle’s linear taper was great for the Wave Distort function– the middle of the treadle was the center. For the speed, though, the fast portion was bunched up in the last few degrees of the treadle. I ended up paralleling a trimpot with one of the gangs of the pot, and adjusted the taper to my liking.
The Shape and Multiple controls are rotary switches. I never liked the idea of using a potentiometer for these settings. Rotary switches are accurate, with no guesswork involved.
The plates are regular ol’ copper clad from Tayda, treated with liver of sulfur. The switch plate and the the treadle plate are secured to the enclosure with JB Weld. It was a bit of a challenge to get the switch plate bent to the contour of the enclosure, but it came out okay. The knobs eventually will be switched out to something nicer, or at least something that matches.
I wanted to do something unique for the LED arrangement. I used a CMOS IC to buffer and filter the PWM from the TAPLFO. The signal is sent to an LM3914 IC, but is first adjusted from 0-5V to a range that works well with the LM3914. It took a lot of trial and error, but the 10 LEDs light up in time with the effect. Those LEDs, and the indicator LED, backlight the plate, and it looks really cool.
This was a very difficult build, requiring a lot of planning and a lot of detail work. It was challenging and fun, but I am glad it is done.
And now, a bit of history on DIY Tap Tempo Tremolos.
Sometime back in 2008, when I was just getting into effects, I started researching tremolos for a multi-effects board I planned on building. In my research, I found the Tremulus Lune. I could understand how the audio path worked, but the LFO was beyond my knowledge.
Around the same time, I found the VCLFO. It is a microprocessor-based LFO created by Tom from Electric Druid. I could understand the VCLFO– feed it values between 0 and 5V, and it alters the waveshape it outputs. I decided to hack them together.
I had no clue how to burn Tom’s code to a PIC, so I enlisted a friend of mine Ed for advice. He is a senior electrical engineer at a big company back in Illinois, and has been a huge help in my quest for electronics knowledge. He often points me in the right direction so I can learn whatever it is I want to learn, but in this case, he offered to burn the PICs for me.
We all know the adage when trying to get something: Cheap, Fast, Right– Pick Two. In this case, it was cheap and right. After months of polite nudging, Ed assigned the burning of my LFO chips to a junior engineer at his company, who burned me five of them.
I did a ton of research while waiting for the chips, and started breadboarding as soon as I got them. I ended up with a design that almost worked. I had one little problem, and Tom helped me out through email. I also was concerned that running multiple LEDs off of the PIC could exceed the PIC’s maximum current, so Ed scratched the transistor buffer on a napkin while he was here on vacation.
I finished my design and released it to the public in June of 2009. People seemed to like it, but I don’t think anyone built one. That’s ok, though, because Tom liked it. He thought my use of a photocell to clean the PWM was simple and elegant. He asked to use my schematic for the VCLFO Tremolo Application Note, and I, of course, agreed.
Some time passed, and Tom posted over at DIYSB that he had started working on a tap tempo version of his VCLFO. I jumped in to the development topic, of course, being the only person who had used the original VCLFO. Tom was great about the development, and incorporated pretty much every suggestion from the community. The community even pitched in on some of the coding (Wave Distort was implemented by Chris Saffi, if I recall the name correctly). Tom eventually released the TAPLFO, and a ready to go tremolo schematic that pretty much matches my original VCLFO schematic. It was so cool!
Some time passed, and Taylor over at DIYSB started a topic to build a tap tempo tremolo. Several ideas were proposed, but the end decision was to use the TAPLFO. One of the key factors was that it was open source and free to use. It didn’t hurt that there was already a completed schematic.
Taylor designed his board, and made an arrangement with Tom to sell them with TAPLFO chips. He released his board (still available), and also the Iron Ether Cygnet (discontinued, I think). At one point, he was worried about using my design for a commercial project, but I think it is great that I played a part in the evolution of tap tempo tremolos.
The TAPLFO has gone on to find its way into a bunch of commercial tremolos, including the Catalinbread Semaphore, and a bunch who I suspect are using the TAPLFO without Tom’s permission.
In parallel to all of that, I had at some point sent a crystal and one of the five VCLFO chips that Ed had made for me to Rick (Frequencycentral), across the pond in the UK. Rick was heavily into phaser development at the time, and I thought he might have some fun with the VCLFO and phasers.
Rick sat on the chip for a while, but when he started using it, great things resulted. Rick has been using (I think) both the VCLFO and TAPLFO to make synth modules. I think he is selling commercial designs and keeping with the DIY spirit by releasing his designs.
So there you have it. My little role in the history of DIY tap tempo tremolos. If you made it this far, thanks for reading!