ggoverdrive

TODO: Update to use released JUCE 6 and then merge with master

Just for fun, I'm trying to simulate the Systech Overdrive pedal from the 70's.

This is an quite rare and odd overdrive with a variable wah-like bandpass filter before an opamp overdrive stage with diode clipping.

The plugin is ok now, but not as the real analog pedal of course.

The plugin uses the JUCE framework https://docs.juce.com/master/index.html. I have only tested the plugin with the Reaper DAW on Windows.

I'm now using JUCE 6 and building using CMake. See https://github.com/juce-framework/JUCE (juce6 branch at the moment of writing) for more info about JUCE and CMake.

The signal chain in the Systech Overdrive consists of (in this order)

• A JFET buffer
• A variable inverting multiple feedback bandpass filter (the "eq" control)
• A "distortion" control (voltage divider to limit signal to the next stage)
• A high pass filter that cuts some bass before the distortion stage
• An opamp gain stage (gain approx 400)
• Diode clipping stage with two 1N4148 diodes in opposite direction connected to ground
• A volume control (the "gain" control, a voltage divider to limit signal to the next stage)
• A BJT transistor gain stage (gain approx. 2)

In the plugin the signal chain looks something like this:

• A variable gain stage (to adjust the incoming signal level)
• Variable band pass filter
• First order high pass filter (to cut some bass before the distortion stage at 300 Hz)
• A variable gain stage (to raise the signal to introduce clipping in the next stage)
• A waveshaper stage to clip the signal (simulating opamp clipping)
• Static gain stage to adjust the signal before the next clipping stage)
• A waveshaper stage to clip the signal (simulating diode clipping)
• A variable gain stage as output level control
• Finally one more waveshaper stage to limit the signal and avoid unwanted clipping in the rest of the DAW signal chain.