simple LFO question

[Jules Ryckebusch]

I have the Tom Henry article and have built the "smooth" Phaser (Got 3 of 'em with
single input pannable outputs most excellent stereo effect) I can post the LFO
portion it is a simple design that uses a FET as a voltage "warper" from a schmidt
trigger triangle LFO. Unfortunately the heart of the phaser itself is a SSM2040, so
the rest of the design is hard to do these days. I can draw up the schematic LFO
portion and post if there is interest.

Jules

"Paul R. Higgins" wrote:

> Electronotes had an analog delay design that used an expo converter to drive the
> high-frequency vco.  I think that I saw it in the "Builder's Guide".
>
> Someone mentioned the Tom Henry phaser design.  This was a DIY feature in
> Electronic Musician years ago titled "The Smooth Phaser".  It used a FET-diode
> circuit very much like the tri-sine converter in some of the Electronotes vcos.
> The nonlinear behavior of the FET was exploited to transform a triangle wave
> into something close to a full-wave-rectified sine.
>
> I have an old Hyperflange unit (the Craig Anderton design), and I can say that
> the sweep does indeed sound exponential, even if the hypertriangular wave is not
> exactly the same as a linear triangle feeding an expo converter.  (The
> hypertriangular shape is in fact continuously variable).  One of the other
> overlooked aspects of the Hyperflange design is its extremely wide
> sweep--something like 72:1.
>
> I remember Anderton saying something to the effect that it's a lot easier to
> make an LFO with an exponential shape than to design a clock circuit that can
> sweep exponentially over a 72:1 range.  It does seem to me, however, that
> feeding a triangle into an expo converter would work the same way.  Maybe I'm
> missing something, though.  My best guess is that Anderton used a CEM3340 to do
> the hypertriangular LFO because it resulted in a much lower parts count when
> compared with an expo converter/LFO circuit; plus, the 3340 LFO could be voltage
> controlled, and even had a sync function.
>
> -PRH
>
> _____________________________________________
> Paul Higgins
> email: higg0008 at tc.umn.edu
> University College, University of Minnesota
> _____________________________________________