Doing it all in 4069s (Was: Re: [sdiy] New Vco (new images))

[Magnus Danielson]

From: "tomg at efm" <efm3 at mediaone.net>
Subject: Re: [sdiy] New Vco (new images)
Date: Sat, 29 Sep 2001 04:26:45 -0400

> Thanks Rene. Using a 4069 was a great idea. It really does
> make a terrific little vco. I played with it some more and put
> it here...
> http://people.atl.mediaone.net/efm3/vco-4069.pdf
> 
> This version has an extended lower range 0.23Hz to 18KHz
> with a very slow ramp. It's scaled as high as I can hear. The
> last octave I can make out runs from about 5K to 9.5K. I
> think I can hear that the 9.5K to 17.5K octave is also correct
> but I'm more than likely fooling myself. Not that it's correct
> but that I can hear it...;-)  I'm pretty sure it's ok.
> 
> Yes it uses a tempco but they are pretty cheap these days at
> $2.50ea...Anyway thanks again this was great fun.

Hmm interesting!

This kind of rings a bell in me, I've actually considered the oddball
idea of building a synthesizer with 4069s as the only active
component.

A 4069 is basically a high gain inverting amplifier. If you look at
the above VCO, you should be able to remove the TL072 by using two
more of the 4069s inverters. Just think of it, it is indeed possible
even if it requires some more thougth.

As for my idea, naturally the exp-transistors can't be avoided.

As for the filter, there is the JHs WASP clone, but I do wonder if not
the CA3080s could be replaced by 4069s if given thought.

VCAs is not problem, a 4069 and 12 1MOhm resistors and there is 6 VCAs
all prewired together to form a mix. Then for the virtual ground
summer completion a single 4069 inverter for the buffering.

For signal and CV summers will single 4069 gates do just fine.

I think it should be possible to do an envelope generator too.

I don't think it will be a high precission synth, but I am quite sure
that one could make one that actually works. I'd like to dub this
synth to 4069.

There is surely a few problems in doing this, but I think those
problems are there to be found and lessons to be learnt.

It is strange what a brain can produce after just getting out of a
hang-over ;O)

Actually, I think I'll start scetch some on this right away... ;O)
Any takers?

Cheers,
Magnus