The E-Whammy Update

Challenges

Since November 2024, when I shared a video clip of the controller in action in my post The E-Whammy: Evolution, the sensor electronics design has remained rock-solid.

The mechanical design was intentionally kept simple. The objective was long-term durability and ease of installation while maintaining a traditional look and feel. But sourcing the mechanism presented some challenges. I’m glad I was able to persuade GOTOH (Japan) to sell me just the tremolo arm and arm socket—they truly make the best bridges and tremolo systems. I love the tension-adjustable arm, with its small hex adjuster at the base that lets you dial in exactly how much resistance the arm offers as you move it.

But then I still had to source the custom steel spring and mounting bracket, both surface-treated. It’s beyond our capability to manufacture these in-house. While black chrome works for the bracket, I realized that the spring’s constant flexing would cause micro-fractures in its plating, so I opted for black electrophoresis instead. After trying several manufacturers—most of which struggled with small precision parts—the final vendor’s samples came very close to our specifications.

Is anyone still interested in bright chrome? It seems to be getting out of favor now?

Your Feedback

My latest post about the E-Whammy went live on April 20, where I clarified what it is—and isn’t—refined the requirements to tighten the project scope, and hinted at availability. I also added a feedback form to gauge interest and explore possible extensions of the scope. For anyone who missed it, here’s a link to the post: The E-Whammy Explained: What It Is (and Isn’t).

Based on your feedback, here’s what I’ve learned so far:

• CV controller: Many of you want to use the E-Whammy as a control-voltage source—especially popular in the modular-synth community.

• MIDI output: A lot of interest in generating MIDI to drive external gear or DAWs.

• Expression-pedal input: A low-hanging feature is direct TRS-jack support for expression pedals (most modern pedals accept CV). I’ll expound on this below.

Expression Input

The E-Whammy offers a natural alternative to a traditional expression pedal. 

Expression pedals let musicians control parameters on electronic gear—digital amplifiers, effects units, MIDI controllers, and synthesizers—using a foot-controlled variable resistor. Unlike volume pedals, which directly alter the audio signal, modern expression pedals send control voltages to the device’s expression input, acting like a remote knob. They’re typically passive (no external power) and connect via a TRS (tip-ring-sleeve) cable.

Most modern pedals use control voltage (CV): the host device supplies a fixed reference voltage on one jack connection (tip or ring), which goes to one end of the pedal’s potentiometer; the other end ties to ground (or to a second potentiometer setting the pedal’s minimum output). The wiper then outputs a continuously variable voltage back to the device.

The challenge is the lack of standardization. Reference voltages range from 3.3 V to 10 V, and pin assignments vary: Roland/BOSS puts reference on the ring and variable voltage on the tip, while most others do the opposite. Exceeding the reference voltage range can damage the input.

To make the E-Whammy function as an expression source, it needs to:

1. Protect against overvoltage
2. Scale its output to common ranges (3.3 V, 5 V, 10 V)
3. Swap between Roland/BOSS and Korg/Yamaha pinouts

We could automate detection with a small microcontroller that senses the reference voltage and pin configuration, then switches the output pins and scales the control voltage accordingly. That said, simplicity has its appeal—a purely analog design, with manual switches for pinout and voltage range plus overvoltage protection, might be preferable. I’m still weighing which approach to take.