[sdiy] Re: Spiral Waveforms

[ASSI]

On Sunday 11 April 2004 16:49, Scott Gravenhorst wrote:
> Once we get away from linear ramps, things get difficult.

Not really, depending from what side you look at it it might actually 
become easier once you switch over to harmonic oscillations.

> Someone correct me if I am wrong, but
> sinewave oscillators don't operate by following a dot as it goes
> around a circle with constant angular velocity.

If they are real sinewave oscillators (not using waveshaping of 
triangles or something like that), this is _exactly_ what they do. 
Otherwise you'd not get a sine from them.

>  Of the difficulties
> involved, it seems to me that there are two main requirements: 1) a
> circuit to establish and maintain the spiral and 2) a circuit that
> can provide a projection of the spiral placing a "light source" at a
> given angle.

You just described a quadrature oscillator and some sort of phase 
interpolation between the sine and cosine to produce the final output 
output. Or equivalently a sine oscillator that can be phase modulated.
The result of using oscillators based on these principles for musical 
purposes is widely known from Yamaha FM and Casio PD synthesizers.


Achim.
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