JonDent - Exploring Electronic Music: NLC Mobius Pill

Saturday, 6 February 2021

This is a continuation of my build notes for the NLC Mobius Pill.

Part one is here;

+ Some info about Vactrols

It's a noise module that combines some Buchla style LPGs with phase locked loops.

The PLLs are two 4046 ics.

There are also some op-amps .

The LPGs use vactrols.

Vactrols are quite simple devices.

They have a light source on one end, and some sort of light sensitive detector on the other end.

These are encased in a light proof box or container of some sort.

The Light is a LED in this case. The detector is a LDR - light dependent resistor.

I chose green LEDs.

The best match I think is between green and green/yellow. A blue LED is the worst possible choice.

Also remember that the same LED colour can vary from one manufacturer to another.

Many commercial vactrols use LEDs that produce infrared light.

These are the light dependent resistors which I used.

GL5549. These have a light resistance of 50K~100K.

and a dark resistance of 5M ohms

LDR type nr 5516.are good too.

These have a light resistance of 5K~10K.and a dark resistance of 0.5M ohms

At the bottom of the page is some data you may find useful.

These are the light proof boxes I made for the vactrols.

I ran out of single row headers, so had to make do with offcuts.and a double header.

Apparently there is a worldwide shortage of headers ??

Jacks and pots next.

Line them up and attach the faceplate before soldering.

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Saturday, 6 February 2021