CA 3080 Tri to Sine converter question

[John Speth]

This circuit is designed around a specific input amplitude for the triangle wave so I believe it's not a matter of what the source of the triangle is but, rather, simply its' amplitude.  It also must have no DC component (unless you AC couple it which probably will be difficult in LFO applications).  Since it has no time dependent elements, it's perfect for LFOs too.  

But this all makes me wonder... A pure triangle wave is relatively uninteresting to listen to and a sine wave even more so.  In an LFO application, I can hardly tell the difference.  As for audio range application of a sine wave, I think it has its' best application when used as a modulation source when you want the modulated sound less rich than what you'd get when using a complex wave.  Or using a sine for one channel input in a ring mod - you'd get a less complex output.

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