Vance Galloway has extensive knowledge of nearly every facet of guitar technology, from pickups to synthesis. He’s one of my go-to buddies I turn to for feedback whenever I’m developing new tech. One of his main concerns is the center stability of the E-Whammy: how the system holds or snaps back to the “neutral” center when the whammy bar is released. Letting go of the bar returns it precisely to zero pitch shift, locking at the center with no drift.
For those who tuned in late, see these posts for reference:
The E-Whammy Update
The E-Whammy Explained: What It Is (and Isn’t)
The E-Whammy: Evolution
Spring-less E-Whammy: Proof of Concept.
My solution is an electronic circuit that locks to center within a user-defined window. The E-Whammy’s control voltage ranges from 0V to 5V, with 2.5V as the dead center. Currently, there are trimmer potentiometers to adjust gain (sensitivity) and offset (centering). I’ve added a third potentiometer, and the corresponding circuitry, to set the width of the center window—the range around center where the output snaps to 2.5V.
NOTE: This is probably the last design change for the E-Whammy, as I’m preparing to start accepting pre-orders.
The circuit uses a window comparator to control a 2-way analog switch. This switch connects the output either to the input signal or to a fixed 2.5 V reference voltage.
The plot shows a simulation focused on the center of operation while tracking a ramp input.
The green plot shows how the output snaps to 2.5 V when the input (X-axis) falls between 2.4755 V and 2.5245 V.
When the input voltage is outside the window, the window comparator’s output (blue plot) is low, allowing the analog switch to pass the input signal through unchanged.
When the input voltage is inside the window, the window comparator’s output (blue plot) goes high, causing the analog switch to connect the output to the stable 2.5 V center reference.
A lowpass filter smooths the transitions between continuous tracking and the center lock state, and also filters out any residual charge injection from the analog switch.