phaser

[Andy Mucho]

Jeroen Proveniers wrote:
>
> last night I was working on my software synth again, and to thicken up the
> sound I added a chorus, which is just a few delay lines of which the delay
> times are slowly modulated. A phaser is almost the same, where a
> very short
> delay (below 10ms) is also modulated slowly, but the effect,
> compared to the
> chorus, is absolutely unsatisfactory. It just doesn't go 'deep' enough.
> What's wrong with my algorithm? My Boss SE-50 multieffector has
> quite a set
> of parameters. Speed and depth are easy. Depth controls the maximum delay
> time. But what about manual and resonance? Probably some filter is
> incorporated. Or some strong feedback path? Or are more delay lines
> neccesary?

I thought Phasers were infact a whole bunch of allpass *filters* in a serial
arrangement. No delay lines, well just the delay of the filters..
Something along the lines of:
 out=in*-f+d1;
 d1=out*f+in;
f is modulated between some frequencies.
So you have an overall setup that looks like this:
 acc=ap1(in+d*fb)
 acc=ap2(acc)
 acc=ap3(acc)
 acc=ap4(acc)
 acc=ap5(acc)
 acc=ap6(acc)
 d=acc
 out=in+(acc*depth);

6 stages, sound good.
12 Stages sound fierce.
24 Stages scared the living daylights out of me :)

AndyM00