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

[houshu at union.cl.nec.co.jp]

Hello Rene, Magnus, Tom and List,

Thanks for very interesting discussion.

What a coincidence.  I tested HADSR using 4049BP on breadboard last
week.  Unfortunately not 4069.  4049 has better driving capability
resulting in fast attack.

http://www5b.biglobe.ne.jp/~houshu/synth/eg0104.gif


For VCF, Pearl phasers may be inspiring.

PH-44 (only core part): 

	http://www5b.biglobe.ne.jp/~houshu/synth/ph44core.gif

By replacing complementary pair of PH44 APF core with a cmos inverter,
we obtain a cmos based APF.  Converting it to LPF is easy.

PH-03:

	http://www.mif.pg.gda.pl/homepages/tom/files/PH-03.gif

In PH-03 (I got one today!), Mysterious IC4 is 4069UBP, which is
used as a hex OTA array.  Possible problem is range of cutoff
frequency.

Hope this helps.

- -- ---- ----------- --- --- - ----- -- --- --- - - ------ - - - --
 Osamu HOSHUYAMA                    NEC Corporation  Kawasaki JAPAN
--------------------------------------------------------------------

> Date:    Sat, 29 Sep 2001 16:05:37 +0200
> From:    Magnus Danielson <cfmd at swipnet.se>

> > 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