Dual Neuron / Difference Rectifier (Papernoise panel)

Analog neuron and difference rectifier circuits

Two NLC Neuron / Difference Rectifier circuits, with a panel by Papernoise.

What is this module? Per creator Andrew Fitch:

The Diff Rect....needs a better name, behaves as per these equations:

V(out)+ = V(in)+ - V(in)- if > 0, otherwise 0
V(out)- = V(in)+ - V(in)- if < 0, otherwise 0
(ignoring diode voltage drop)

Basically the voltage on Vin- is subtracted from the voltage on Vin+. The value left then goes to Vout+, if it is more than 0V, or to Vout- if it is less than 0V.
So, as the name implies you are getting the difference between the input signals and that difference is then rectified to the +ve or -ve outputs.

As there are no caps in the signal path, it will happily deal with audio rate signals as well, so is an interesting waveshaper and even acts a bit like a VCA....let's say audio gate hihi
For me it is most fun just to feed it signals from LFOs and get a lot of complex envelopes from it.

The neuron is from "A general purpose analog neural computer" by P. Mueller et al and modified for use in a synth. The circuit is an "idealized version of a typical biological neuron." It feeds thru the postive rectified portion of the input signal and mixes that with positive and negative going pulses (or spikes or gates) when the threshold (set by the offset pot ) is crossed.
The 1st op amp stage is a summing rectifier. This stage output is fed to a comparator, the inverted positive rectified signal and the comparator output, via an attenuator, are summed and inverted at the final output stage.

The offset pot determines when the comparator will 'fire' in response to the input signal and the invert pot sets the level of the signal from the comparator going into the output stage.

Sorry, this description probably doesn't help.

(From https://www.muffwiggler.com/forum/viewtopic.php?p=981677#981677)