[sdiy] Simple VCO: 4069 or 7555

[René Schmitz]

Hi Dave, and all

At 09:34 15.11.01 -0500, Dave Magnuson wrote:
>After playing with my SH-101 for a while, my 7 year old daughter decided
>she wants a monosynth.  Err, umm, actually, after playing my SH-101, I
>decided I WANT IT BACK, so I'm building her a monosynth to keep her
>occupied so I can go steal it!

:->

>I have enough left over circuits here to build almost the entire project
>already (LFOs, EGs, VCFs, VCAs).  The only thing I'm lacking is a VCO.  I'd
>like to keep this VERY simple, and scalability isn't too important (I can
>build a better VCO later if it ever becomes an issue).  I'd like maybe 2 or
>3 octaves of range, so I'm thinking of trying the 7555 or 4069 based VCOs
>that we've been discussing lately. 

You can get 7 or 8 octaves out of the 4069, should be enough.

>What are people's opinions of the SOUND of these two oscillators?  I know
>Scott G has heard both for sure... anyone else want to say which design
>they think *sounds* better?  I'd prefer to build the VCO with the most
>"character".  I know this is a very subjective matter, but...

I think the 4069 has plenty of character, its saw is slightly imperfect, 
and the pulse is also very round, almost as sloppy as the 303-type pulse. 
I can only compare to the (7)555 based designs at my site, and those have 
more precise waveforms.

Cheers,
 René



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uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159