Octature osc?

Jim Johnson jamos at technotoys.com
Fri Sep 4 17:24:08 CEST 1998


Regarding a true octature oscillator for Shepard applications - how about
using the sawtooth phase splitter from Electronotes (I can't remember the
precise name of this circuit) and then driving a set to saw to tri
convertors? Saws and triangles are what is needed for the classic Shepard
effect - 

Re a triphase oscillator - if you have good, pure sines in quadrature, then
it should be possible to create any arbitrary  phase by mixing the sine and
cosine components with the proper levels and inversion. For example, a 45
degree sine can be obtained by mixing the sine and cosine in equal amount.
A 120 degree would be a mix of the 180 degree (inverted) sine and the
cosine, etc.

I want to build a quadrature LFO at some point. I have not looked at JH's
schematic yet - is it suitable for low frequencies (say, down to 0.01 Hz?)
I can across a schemo for a VCQO at Analog Devices (based on the AD633)..
might this be suitable for use as a VCQLFO?




*********** REPLY SEPARATOR ***********

On 9/4/98, at 3:09 PM, jorgen.bergfors at idg.se wrote: 

>I would like a three phase LFO. Any ideas how to make one? I already have
one 
>that use all pass filters to get 120 degrees  phase shift, but it only
works 
>right for a very limited frequency range.
>
>/Jorgen
>
>
>
>
>
>MIME:Hcabnivek at aol.com on 98-09-04 16.04.44
>To:  synth-diy at mailhost.bpa.nl @ SMTP 
>cc:  (bcc: Jorgen Bergfors/IDGSE)
>Subject: Octature osc? 
>
>Does anyone out there know of an available design for an octature 
>osc/lfo?  My
>understanding is that this is necessary for generating Shepard 
>functions. (?)
>thanks,
>Kevin

Jim Johnson 
Metaphoric Software
-------------------
Makers of Techno Toys
Software for Electronic Music
http://www.technotoys.com
info at technotoys.com




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