JFET Guitar Wah Pedal — Look Ma, No Inductors!
- JC - Linear Systems
- 2 days ago
- 1 min read
JFET Design Spotlight
🎸 “JFET Guitar Wah Pedal — Look Ma, No Inductors!”
The variable band pass filter for musical voicing effects most notably, the Cry Baby from VOX, became famously known as a WAH Pedal. The original WAH used a 500mH inductor in a feedback loop to produce a variable filter with foot-pedal potentiometer activation. Issues with this pedal were, few were much alike. This design variation of the WAH effect is to eliminate the inductor having varied Q’s making most all Wah Pedals different. By substituting a bandpass filter designed at General Radio by Henry Hall in 1952 for Null Meters, a more uniform distributed gain over frequency could be realized. Incorporation of this technique makes for an unusually clean sweep and low noise effect for Lead Guitar, Bass, with 3 capacitor swaps, and any other Funkadelic need worth messing with. The Linear Systems LSK389s make implementation of this low loop gain JFET OP-Amp remarkably linear and highly musical. Loop gain may be cheap but doesn’t necessarily sound good. For Audio, Linearity certainly does!” Kirkwood Rough
What’s your preference for tone shaping — classic inductor wah or active filter designs?
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