A Discrete Design for a Guitar Compressor

“8 years were spent working with, and listening to, a cadre of guitarists debating various pedal sound effects. Most debated was the lowly Compressor. Orange squeezer, MXR Dynacomp, Ross, Boss, and on and on. The simplest of all were those like the Ross compressor with a CA3080 OTL IC, (operational transconductance amp) used as a variable gain amp for leveling the transient amplitude input of an electric guitar. These designs had a couple drawbacks, being, to slow of an attack and distortion from the OTL being initially differentially overdriven. A correction might include phase control, linearization of the OTL input and a cleaner OTL. To settle the OTL style debate a discrete electronic approach was built; it incorporates a JFET input impedance buffer presenting no appreciable load to the guitar, a pair of biased diodes to AC linearize and precompress the OTL input, a discrete OTL amp using matched dual Linear Sys transistor pairs and high gain Linear Sys Bipolars for the compressor control. The final circuit having over 20db of compression range proved to be significantly quieter, had little “Pop” in the attack, and much less initial compression distortion lending to a more musically friendly sound. Using combinations of Linear Systems dual and single JFETs and the array of low noise dual Bipolar transistors allows all of my audio designs to perform to the highest level expected and in the blind shootout test of 5 OTL candidates at Upstairs Amps and Brawer Guitar, this design was remarked as , “ Yeah, that’s what I’m Talkin about!”. Feedback on this is always appreciated.” - Kirkwood Rough

Designs like this highlight what’s possible with low-noise JFETs and precision-matched pairs. If you’re working on audio circuits, Linear Systems JFETs are a great place to start.

Request samples HERE.