aciddose wrote:The difference between inputs vs. outputs is how the non-linearity affects it as well as signal phase.
Oh sure.. I was just thinking about the linear solution.
In the ladder filter you need to mix 5 signals (since you have 5 freedom degrees in the numerator). The 5th signal can be picked up either before the feedback point (that is the input signal) or after the feedback point (the input to the first stage), the latter usually results in simpler expressions. It's the same how in an SVF you have 3 freedom degrees, the HP signal essentially being the "input signal".mystran wrote:I don't think using both inputs and outputs really ever gets you anything as usually either alone will let you place your zeroes however you please and when you manage to hit a singularity it usually affects the inputs and outputs the same. That's my experience at least.
IIRC it's pretty straightforward to work backwards (pun not intended ) from the last stage (for which we already have the answer), you don't actually need the state-space form for that.mystran wrote:With regards to the diode though, keep in mind that you can't use the simplified math for the buffered cascade to calculate the coefficients, because the responses at the poles are not just (1/(s+1))^n anymore. Instead you need to solve for the actual responses of the individual poles (this is probably easiest to do with the state-space form) and then use those to solve the zero-placement.
Z1202 wrote:Then why don't you do that? Do you have any specific questions? Actually, I think at least partially the differentiators have been successfully used in filter models:1eqinfinity wrote:I'm interested in the implementation of those differentiators on the block diagram.
http://dafx13.nuim.ie/papers/44.dafx201 ... ion_56.pdf
Although personally I would have built a fully integrator-based model. Not sure if there is any difference arising out of that in the final model in this case
With regards to the diode though, keep in mind that you can't use the simplified math for the buffered cascade to calculate the coefficients, because the responses at the poles are not just (1/(s+1))^n anymore. Instead you need to solve for the actual responses of the individual poles (this is probably easiest to do with the state-space form) and then use those to solve the zero-placement.
Hello again, everyone
Am I right that it's ok to build pure (not multimode) HP ladder using lowpasses, but taking (in - lp) as the filters' outputs?
The underlying filters are then processed as lowpasses, but the Gn and Sn for the whole ladder are derived from yn = xn - (g(x - yn) + sn).
ncthom wrote:The algebra shakes out very similarly, and it's easy enough to program, but as soon as I set a feedback (`k`) value higher than 0 I lose the notches in my phaser and get a pretty unstable peak. Have I taken the wrong approach for resolving the feedback loop here?
Z1202 wrote:Among other stuff, the book provides "research documentation"
The point is stated in the chapter titlesmystran wrote:I had a quick browse through most of it and frankly I think some of the stuff (especially chapters 9 and 10) reads pretty much like "research documentation" where it presents a lot of mathematics without really making it very clear what the actual point is. That doesn't necessarily mean there isn't a point, just that it's not very obvious.
Well, this is one kind of nonlinearity present in OTA models. I didn't do a proper modelling of OTAs themselves, but a discrete-component analog model of an OTA-based ladder, which I did a surface analysis of, featured this kind of nonlinearity due to its usage of a differential transistor pair. Also IIRC this kind of saturation appeared in Huovilainen's models of OTA-based structures. I definitely do not claim that this is a complete model of an OTA or even any kind of an attempt at that. "OTA" is more like a label for this particular way to introduce nonlinear behavior. Probably this is not clearly phrased in the book, so I might consider making it more clear in later versions. The nonlinearity itself though is quite useful, as it provides a different kind of cutoff variation than with transistor ladder.mystran wrote:Also I feel like the treatment of non-linearities reads a bit like an "overview of methods" rather than a very practical guide... and the OTA 1-pole is non-sense (ie. the input non-linearity is not necessarily even that significant in some circuits and this thing isn't even necessarily stable under high gain because it lacks the actual limiting non-linearity at OTA output; I'm honestly not sure how to do better without introducing an explicit notion of current vs. voltage though).