CA 3080 Tri to Sine converter question

[Scott Bernardi]

The CA 3080 sine converters are very sensitive to the level and DC offset
of the triangle wave coming in. How the triangle is created really doesn't
matter., as long as the incoming levels are approximately the same.
They work by overdriving the differential pair input of the 3080 into
nonlinearity, with the effect of "rounding off" the tops and bottoms of the
triangle. The "waveform adjust" on a sine shaper will adjust the amplitude
of the signal coming in. Thus a +/- 10v peak triangle coming in will round
more than a +/- 5v peak traingle.
The "symmetry adjust" is actually just balancing out any DC offset in the
input waveform and/or offsets in the 3080 so that the nonlinear distortion
is symmetrical. A DC offset waveform, such as a 0v to +10v sawtooth, would
warp on the top end and be sharp on the bottom.
You could put any waveform into the since converter and get a rounding
effect, which will have the effect of removing higher harmonics, >kind< of
like a tracking VCF, except it would also induce some nonlinear harmonics. 


At 09:07 AM 5/20/98 -0400, you wrote:
>Hi all
>
>I was thinking about those CA 3080 tri to sine converters in Barry Klein's
>book recently, and it occurred to me that rather than build one into each
>oscillator, it might be nicer to have a few undedicated converters sprinkled
>throughout one's system as independent waveshaping modules. Has anyone tried
>this? Will it put out a good sine wave from a variety of different triangle
>sources (such as 3340, ARP, ASM-1 LFO), or does each converter need to be
>"tuned" for each oscillator? It may also provide interesting timbres for non-
>triangle waves. Maybe you could have (switchable) front panel controls for
the
>shape and symmetry.
>
>Just a thought.
>John B
>
>
--------------------------------------
Scott Bernardi
voice: 415-538-0439 (note new number)
fax:   415-904-8375
scott.bernardi at fritz.com