[sdiy] analogue DX-7-style Phase Modulation using quadrature signals ?

[jhaible]

Hi Don,

looking forward to see your circuit!

But the method I suggested with the dome filter, after sleeping a few hours
it doesn't look that good anymore.
With that A sin + B cos equation I can get any _wrapped_  phase, but not
any _absolute_ phase, so it's probably limited to delta_phi < Pi.

JH.

-----Ursprüngliche Nachricht-----
Von: Don Tillman <don at till.com>
An: jhaible <jhaible at debitel.net>
Cc: <synth-diy at dropmix.xs4all.nl>
Gesendet: Sonntag, 26. Oktober 2003 02:13
Betreff: Re: [sdiy] analogue DX-7-style Phase Modulation using quadrature
signals ?


>    > From: "jhaible" <jhaible at debitel.net>
>    > Date: Sun, 26 Oct 2003 01:51:04 +0200
>    >
>    > This is just an idea at the moment, and I wonder if this
>    > would work. It's about making DX-7-like Phase Modulation
>    > (often misnamed as Frequency Modulation) with analogue
>    > oscillators. From earlier discussions on synth-diy I know that
>    > FM of a VCO is easy, thru-zero FM is difficult but possible,
>    > but PM - easy in digital - would be most demanding on an
>    > analogue VCO.
>
> Hi JH!
>
> Yes, this is absolutely right.
>
>    > But what about using a quadrature signal?
>
> It's possible to perform voltage controlled phase shift with my
> Quadrature Trapezoid VCO.  That was, in fact, one of the goals of the
> project, and I hint about it in the article.
>
> I have a circuit to do this worked out, but it hasn't been tested yet.
> It's intended to perform graceful Quadrature Trapezoid phase shifting
> over 16 cycles.  The circuit is somewhat complex and took a long time
> to design.  I'll publish it as soon as I know it works.
>
>   -- Don
>
> --
> Don Tillman
> Palo Alto, California
> don at till.com
> http://www.till.com
>
>