Re: [sc-users] Re: Resonz x Ringz (gain issues)

[Julius Smith <jos@xxxxxxxxxxxxxxxxxx>]

At 02:54 PM 12/20/2014, Alexandre Torres Porres wrote:
> HI, meanwhile I digest and sort
> about the ring decay time, something called my attention. By looking at
> the code.
>
> "y0 = ZXP(in) + b1 * y1 + b2 * y2;
> Â Â Â  ZXP(out) = a0 * (y0 - y2);
> Â Â Â  y2 = y1;
> Â Â Â  y1 = y0;"
>
> I can't see how it is a two pole and two zeros filter. I only see
> feedback coefficients (b1 * b2). What am I missing? Or is it a two pole
> with no zeros?

The term y0-y2 straddles two samples, giving a zero at z=1 and another at
z=-1, as needed for the constant-peak-gain property.

- Julius

Julius O. Smith III <jos@xxxxxxxxxxxxxxxxxx>
Professor of Music and, by courtesy, Electrical Engineering
CCRMA, Stanford University
http://ccrma.stanford.edu/~jos/