On 05/30, Dario Sanfilippo wrote:
>
> I was meaning to also implement the ZDF 4-pole ladder. Will Pirkle resolved
> it into this diagram:
> http://www.willpirkle.com/Downloads/AN-4VirtualAnalogFilters.2.0.pdf.
I can't read the diagrams, but the code looks simple... the faust implementation
is trivial:
moog(fc, Q) = tick ~ (_,_,_,_) : !,!,!,!, _ with {
tick(s1,s2,s3,s4) =
lp(s1, u) : _,(lp(s2) : _,(lp(s3) : _,lp(s4)))
with {
k = 4 * (Q - 0.5) / (25 - 0.5);
g = tan(ma.PI * fc / ma.SR) <: _ / +(1);
sigma = g^3*s1 + g^2*s2 + g*s3 + s4;
u = -(k * sigma) : /(1 + k * g ^ 4);
lp(s,x) = y + v, y with {
v = (x - s) * g;
y = v + s;
};
};
};
although I didn't check this code and I am sure it has mistakes.
I am wondering what are you going to do with it ;) and how to compare this code
with moog_vcf_* in vaeffects.lib.
Oleg.
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