[sdiy] Temperature stable lin-exp converter with a CA3086 or CA3046

[Sowa Roman]

All this talk about exact compensation got me thinking.
Does it really matter if overall VCO performance is 50
or 100ppm/K because of not exact tempco, or other components
temperature response? Standard crystal oscillators are specified
to have 50ppm (not talking about those expensive 2ppm here)
and they are the source for 'boring' DCOs. So are we going
the right path? Someday one may say "those VCOs we have
nowadays are so boring, DX7 - this had a drift!"

And now about Tim's idea of coreVCO. I'm thinking about
same thing for some time now. I want to make it even more
simple. Just expo converter, integrator, comparator, FET.
CV with response 0.5V/oct able to cope with multiple inputs
summed before getting into coreVCO and fitting inside +/-12V
rails, one output (saw). Cap would be external, so one could
use it for VeryLowLFO as well as RF VCO ;)
All squeezed on small PCB size, say, 1x1cm. And dipped in epoxy.
Premium components of course.

Then why stop here. coreVCFs, and others, similar blocks
with waveshapers, output buffers, input bipolar attenuators
and we have LegoLikeSynth :)

someone stop me please...

Roman

__-----Original Message-----
__From: Tim Ressel [mailto:madhun2001 at yahoo.com]
__Sent: Monday, May 27, 2002 8:17 PM
__To: Sowa Roman; SynthDIYmailinglist
__Subject: RE: [sdiy] Temperature stable lin-exp converter with a CA3086
__or CA3046
__
__
__To all,
__
__All this talk about expo converters got me thinking:
__It would be nice to have a core VCO design. Just an
__expo convertor and a sawtoth oscillator. Question is
__what features would be needed to make it ultra-useful?
__
__My personal list:
__
__*  Cheap as possible
__*  At least 5 expo ins, with at least 3 super-matched
__*  Linear in
__*  Hard and soft sync
__*  Ready for stand-alone use
__*  Scalable for any system (CV and sig levels)
__
__I'm sure there are others. I think having a PCB like
__this would be a great goodness. An add-on board would
__do the wave-shapers.
__
__--TR
__
__


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