Tuesday, 1 September 2015

Vactrol Pill - NLC - Build notes

These are my build notes for the nonlinearcircuits Vactrol Pill module (eurorack format).
It's a very easy build  & there are no surface mounted components.

The vactrol can be home made if you like. Just a LED & a light sensitive resistor housed in a light-tight package is all you need. Andrew F has a page on how to make these.
http://nonlinearcircuits.blogspot.com.au/2015/08/diy-vactrols.html

Andrew's build notes are here:
http://www.sdiy.org/pinky/data/WAMOD%20PiLL.pdf

The Pill refers to a PLL or phase-locked loop. This type of circuit consists of a variable frequency oscillator and a phase detector. The signal from the phase detector is used to control the oscillator in a feedback loop
so that the phase of the oscillator is constantly matched to the phase of the incoming signal.
I usually start installation with headers (IC & power), then resistors & caps.

This module uses a 4046 chip.


I'm using a Silonex NSL-32 vactrol. They are cheap as chips. The white dot marks the cathode of the LED part of the vactrol. Andrew has labeled this as "K" on the PCB.


It's now time to install the 3.5mm jacks.

 Screw the panel in then solder the jacks


Don't forget to solder the ground tabs with scrap wire.
After soldering the LED you are done. :-) So easy !!!


If all is working, the LED should light up in sync with a gate signal. The top two inputs (in1 & in2) are for gates & CVs. The 3rd input (pm) is for audio.The audio signal is phase modulated by the PLL

There are 2 outs ... the "pm out" is of course the phase modulated version on the inputted audio.

Links
1. Building a VCO using a 4046.
2. The X-4046 VCO - Thomas Henry
3. Simple CD4046 VCO - electromusic
4. Muffs post
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