[sdiy] 4069UB based CV-ADSR

[Magnus Danielson]

From: "tomg at efm" <efm3 at mediaone.net>
Subject: Re: [sdiy] 4069UB based CV-ADSR
Date: Sun, 30 Sep 2001 02:58:15 -0400

Tom,

> Very cool Magnus..I think it's very close to working!

Thanks! Yes, it probably is quite near working state. As a first
scetch on such a thing and using properties that I am not well
familiar with I think I can be kind of proud. I will refine it
further. My lack of 4069s here at home is naturally a limiting factor.

> Pins 1,5 and 11 need to be held close to gnd so the fets have a drain.
> Maybe a 470ohm - 1K resistor on each?

Possibly.

> I think 1M is too low for feedback and too high 
> for input maybe 2.2M and 100K.

Eh. The U2 is not being used as a inverter biased as a linear curcuit,
it is being used as a bunch of suitably connected FETs and the 1M
resistors is there to do the linearisation trick on those FETs.
In the linearisation trick is the input-to-gate and drain-to-gate
resistors equal.

> Those 1K resistors might kill your 
> voltage level so maybe use those extra inverters to bring the level back 
> up before the output stage..

Indeed a good idea. I allways though that they may come in handy
later.

The interesting thing is that I am utilizing no less than three
totally different aspects of the 4069, for logic/non-linear (U1), for
linear variable resistors (U2) and as a linear inverting amplifier
(U3). Their usage of power lines are totally different.

> I really don't know for sure I'm just throwing things out there. The concept 
> looks sound. I think it's gonna work with a few small modifications.

Indeed. I will need to spend more cycles over this and also take it to
a lab session.

> Well done! Your gray matter is as sharp as ever. 

Thanks! Many thanks!

I hope this acts like an inspiration to others.

Cheers,
Magnus