Arbitrary phase calculation (was: Ensemble Circuit Configuration Questions)

[Martin Czech]

:::> forgotten the original title). It is just combining pwm with a saw wave
:::> (same frequency, pwm average is null) and gives multiple saw waves with
:::> the same frequency , but arbitrary phase. Perhaps this scheme could be
:::> changed to work with triangle waves, I don't know yet, if not, well use
:::> a saw->tri converter.
:::
:::Indeed, this is a neat solution. Note however, that here nonlinear shaping
:::is needed anyway to obtain the sinusoidal LFO output. And speaking about sin-
:::usoidal modulation, I personally would prefer using smooth "true" sine waves 
:::(like those obtained from Wien bridge or quadrature oscillator) for pha-
:::ser/chorus delay modulation. In fact, I don't like piecewise-linear approxima-
:::tion of the sine in this very application. Why ? As the perceived detuning 
:::effect is proportional to the first derivative of the BBD delay, using piece-
:::wise-linear sine approximation results in unpleasant piecewise-constant 
:::detuning with almost abrupt steps between consecutive segments.


Hmm, I see.
If the piecewise approximation causes trouble: An overdriven differential
amp (CA3080) has about 1% distortion, the remaining step in the derivative
at peak levels can be cured with an additional differential branch,
like the circuits on my web site.

A Wien bridge always has trouble when you change the frequency,
because the gain changes , too. So the servo loop needs
some time to settle, and this can produce funny waveforms as well.

State variable things: 

why not trying a (stable) bandpass state variable with pulse wave input?
If you have several such circuits you only need a shift for the 
input pulses, the filters will follow. Of course: tracking problems
for high Q as well...

m.c.