Dual Neuron / Difference Rectifier (papernoise panel)

A module combining an analog neuron and a differential rectifier circuit

A DIY module combining a dual analog neuron and a dual differential rectifier circuit.
The NLC Neuron was inspired by a paper on neural computing and is a variation of a typical analogue neuron circuit. It can be used as a complex audio waveshaper, gate or pulse generator, CV shaper or to generally screw things up.

Overview

This neuron was inspired by a paper on neural computing and is a variation of a typical analogue neuron circuit. To use it: put some LFO and/or EG signals on the inputs, or maybe something from a sequencer. Use the output to control pitch on a VCO or cut-off on a VCF – or anything else you can think of. Twiddle the pots until it sounds good. It will even work with just one input signal, although is much more interesting with two or three. It can also handle audio frequencies, so try it out as a wave-shaper. Feed it two or three signals from different VCOs and let them fight it out. Or feed it a VCO signal and a slow envelope or LFO to modulate the audio. Just some ideas, if you find some other uses, do share!

This circuit is slightly changed from the one on the double neuron PCB. The weight of the offset voltage is halved by the 200k resistor, this gives the pot a more useful range and limits the offset to VCC/2.

DIFFERENCE RECTIFIER This circuit is a hybrid of two basic op amp ‘building blocks’ – a difference circuit and a rectifier. Not sure if I have ever seen the two merged together before. It is probably a bad idea except for synth use, where it is a wonderful idea!

Basically the circuit compares the voltage on the ‘-‘ inputs with the voltages on the ‘+’ inputs. The difference between these voltages is fed to the outputs. If the difference is positive it appears on the ‘+’ output, if the difference is negative it appears on the ‘-‘ output. Again, a great way to mix boring CVs to get something interesting, audio frequency wave-shaping and it also can be used as a crude VCA.

http://nonlinearcircuits.blogspot.com.au/2012/11/neuron-difference-rectifier-pcbs.html