Here’s something for the pedal nerds. This is a pair of back-to-back clipping diodes connected in parallel, like you find in the Rat distortion pedal. One diode clips the positive-going side of the wave, the other clips the negative-going side. They’re fed by a .047uF coupling cap and 1K series resistor.

The scope trace shows a large sine wave (8Vpp), which is the input signal before the coupling cap. The smaller signal is the clipped output. The negative side has the diode connected directly to ground, so the clipping is hard and fairly rectangular. The positive side has a 390-ohm resistor in series with the diode to ground, so the clipping is much softer.

What happens is: The negative side shunts to ground directly when the amplitude exceeds the diode’s turn-on voltage. The positive side forms a voltage divider with the 1K series resistor and the 390R shunt resistor, when the amplitude exceeds the turn-on voltage. Compression! Easy way to broaden the knee of a diode clipper.

Atomium Amplification, Philadelphia, PA

Atomium Amplification specializes in the repair and modification of musical instrument electronics, particularly tube amps for guitar and bass. My goal is to provide affordable repair and modification service directly to Philadelphia-region musicians, in a way that is transparent, honest, and affords an opportunity for the user to learn something about the equipment in question. I like to work one-on-one with individual musicians, in person where possible. I have experience with tube and solid-state guitar and bass amps, all sorts of effects processors, PA and pro sound reinforcement equipment, studio recording, tube and solid-state hi-fi, loudspeaker design, and electronics and setup of guitars and basses. I can probably also fix your bicycle. Email atomiumamps@gmail.com for more information.

Electronic States

1 year ago

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Atomium Amplification, Philadelphia, PA