CA 3080 Tri to Sine converter question

[R.Fahl]

I'll throw in my two cents worth:

I've built both types of tri to sine converters.  Thomas Henry's Deluxe VCO
(published in Polyphony long ago) uses the 3080 approach.  Pretty much plug
and play.  On the scope the output waveform was pretty damn close to a
perfect sine wave.

I built a pair of Electronotes through-zero vcos which use the FET
approach.  On the scope there's little "humps" that I couldn't get rid of,
but sonically, I couldn't tell the difference.

Romeo


>Electonotes did a study on distortion of both FET and 3080 tri to sine
>converters (I'm not at home so I don't have the reference with me). If I
>remember correctly, the FET converter gave less than 1% THD and the 3080
>about 1.5% - not too bad, actually. The 3080 had better THD when there was
>still a slight point left in the tops and bottoms of the waveforms.
>I'll look up the references when I get home.
>
>
>>My concern when implementing the Tri-Sin converter is "Just how pure is
>the sine output?"  On the scope it *looks* good but I lack the
>instrumentation to really measure the purity.  Can anybody quantify the
>purity of the sine output for an optimized Tri-Sin converter using a 3080?
>>
>>John Speth
>>Object Engineering, Inc.
>>johns at oei.com
>>
>>-----Original Message-----
>>From:  JWBarlow [SMTP:JWBarlow at aol.com]
>>Sent:  Wednesday, May 20, 1998 6:07 AM
>>To:    synth-diy at mailhost.bpa.nl
>>Subject:       CA 3080 Tri to Sine converter question
>>
>>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