I like gritty distortion. By using a couple of diodes to clip a signal we can build a passive clipper distortion unit. In this example, I use bipolar LEDs to do the clipping. Even though we end up with a drop in audio level it sounds pretty decent.
In the circuit below I use two bi-color LEDs in series to clip the parallel 1 Hz sine wave signal. The signal is 10 Vpp as is the default case in Eurorack. After the clipping circuit has done its magic, we’re left with about 6.5 Vpp. We could amplify that later of course.
This sine wave looks pretty clipped. But how does it work?
How does a Clipper Circuit Work?
This circuit clips all incoming signal to about 6.5 Vpp. So as long the signal is below that threshold, no clipping occurs. The LEDs stay off because the forward voltage needed to drive the two LEDs hasn’t been reached yet.
When the signal goes beyond the threshold something interesting happens. We open a path to ground through the LEDs. A part of the incoming signal voltage is used to light up the LEDs. This results in a clipped signal at roughly the forward voltage needed by the LEDs. In this case 6.5 Vpp.
Audio Clipper Circuit Demonstration
In the video below I play a little snippet of the excellent Art + Music + Technology podcast by Darwin Grosse. Before sending the signal through the circuit I amped it up to 10 Vpp with the Mutable Music Things Ears Eurorack module.
I like it 😃