Friday, 19 October 2012

A-162 CV Mod

How to add voltage control to Doepfer's dual trigger delay without vactrols. Another chapter in my A-162 mod saga.

Having changed the timing caps for delay and length, there's just one thing left: voltage control over those parameters. Vactrols are an easy, if expensive option. Ray Wilson has a cheaper solution.

Using a FET as a variable resistor is not without its difficulties, but Ray's circuit works with the A-162. It's not precise, but the object was just to get some automated variation.

The floating perf-board is held by a combination of resistors, shrink-wrap and single-core wire. It weighs next to nothing, so should be ok. There was just enough room for the jacks.

Vactrols slew and need 2V before they get going. Transistors operate as resistors only within a limited range. Next time I'll tell you how I added VC to my A-143-1 quad AD envelope using a combination of the two.


Citric Acid - Acid Jack Rec. said...

that sounds nice navs. i will do this mod. do you have a audio demo? thanks for sharing this.


dcp said...

Hi, nice and easy mod. Can you tell us which version of the BF245 you used here? There are three variations available of this part, A, B and C...

Navs said...

I used 'B', but only because that's what I had at hand.