How would you configure and use [bob~] to demonstrate what the ladder filter fuss is all about? For some reason (inexperience? poor taste?) I keep returning to [vcf~].

Edit: after an hour or two of monkeys at the typewriter, I'd say that the 2 main differences from [vcf~] are the roll-off slope ([bob~] never completely mutes signal even when the cutoff freq is 8 hz) and the resonance sounds brighter and grittier (bob at resonance 3 sounds like vcf at q 22 to me). There's got to be more to it than that, right?

Yes i have 60% CPU saving Boca! expr~ sucks also more details in the sound in my opinion!

@tungee nice, makes the [lop~] version of my morphing filter barely even register on the cpu use. Will rework it to suit and include it in my next go around. What you hear as a difference is just that you shifted the q range which gives you more control in the area you are interested in, playing with the division in the [expr~] will yield the same results at. The /5 was picked for the morphing filter since high distortion self oscillation range emphasizes the morphing nicely, but at cost of more traditional resonance sounds, putting the sliders max range at 5 makes it easier to get the more traditional sounds.

Build a automatonism modul out of your abstraction Bocanegra. with modulation inputs preset saving midi controlling etc.

I really like it how it sounds

Here is the automatonism module with install instructions and the modul itself:
Boca-Ladder.zip

Thank you for your explanations oid

I made also a clipping module for automatonism with various clipping algorithms
There you can hear the differences from one algo to the other on the fly oid.

clipper.zip

@tungee why havent you posted these wonderful clipping algorithms in the sigmoid thread -> https://forum.pdpatchrepo.info/topic/13544/sigmoid-functions

Good question Bocanegra

@tungee Ignore my explanation, turns out mine does have anemic resonance, side effect of the 10 sample delay that worked into the feedback path somehow, I had tuned everything to compensate for that 10 sample delay. The explanation was half right, but @bocanegra explained that part already.

Bytheway an excellent thread you made here both oid and bocanegra
Nevermind oid

little note: your filter does not resonate at the cutoff frequency.
top: how it should be, bottom: how it is

now, solve this

@solipp If you have a solution why don't you share it? What is going on inside the second [pd ladder] sub patch I wonder...

Experimenting a bit, it becomes obvious that resonance screws with the filter gain coefficient

Using these crazy ass formulas for filter gain and and feedback I get correct frequency response at resonance close to 1:

Source: https://www.researchgate.net/publication/241280072_POWERWAVE_-A_HIGH_PERFORMANCE_SINGLE_CHIP_INTERPOLATING_WAVETABLE_SYNTHESIZER

It looks like this when I implement it:

I know it aint pretty... It also beefs up the CPU use quite a bit, which I sort of dealt with by by keeping it in a sub patch with normal block size and no oversampling. Another downside is the soft clipping has got to go- it screws up the precision.

I wonder if there is a simpler way to approximate this stuff...

Anyway, have fun finding all my design flaws 4plop~.pd

I wonder if there is a simpler way to approximate this stuff...

Turns out there is. A bit of polynomial magic and I got rid of the [exp~] module

Also ditched the resonance/feedback formula as I didn't see it making a greater difference in frequency response than it did in CPU usage

Updated version with precise response at resonance around 4 and cut off < 11025Hz - still no soft clipping...
4plop~.pd

Hi boca can you provide the whole patch?

@tungee said:

Hi boca can you provide the whole patch?

I already did in my last post

@bocanegra said:

Updated version with precise response at resonance around 4 and cut off < 11025Hz - still no soft clipping...
4plop~.pd

I dont understand, there is only one input . Shouldnt be 3 inputs there (signal input, cutofffreq and rsocnance)?

That is the coeff sub patch you are looking at. This is what I get when I open the attached .pd file from here:

Ah ok now its clear, there was a subpatch ok. If i use this in my automatonism module, it fires up when dragging the slider some Nasty highpeaks. So i installed the anaclip again in it.
Also: the patch of yesterday was stable until 8000hz at 5 resonance. now i can go upto 11khz and reso 10 . Thats nice! GREAT JOB BOCANEGRA :DD

@bocanegra http://www.willpirkle.com/Downloads/AN-4VirtualAnalogFilters.2.0.pdf is a good read. I translated the TPT laddder filter to pd in the [pp.ladder~] object in audiolab (you can download it with deken). Here is a version with an outlet for each pole and the "analog clipper" from above : TPT-ladder.pd
Another solution is [bob~] of course : https://github.com/pure-data/pure-data/blob/master/extra/bob~/bob~.c

@solipp The first link returns an empty pdf...

But thanks a lot anyway. http://www.willpirkle.com/Downloads/ has a lot of useful stuff. Never knew about TPT filters. Also, I have added your audiolab abstractions to my library long time ago and learn a lot from going through the patches seeing how stuff is done- but the content is massive so I haven't sifted through even 10% yet

A question: in 4plop above, there's 1 - coefficient done separately four times. Couldn't this be optimized by doing [*~ -1] --> [+ 1] only once and feeding that result into the 4 rpoles? Bc it looks to me like they all get the same signal input.

hjh

@ddw_music said:

A question: in 4plop above, there's 1 - coefficient done separately four times. Couldn't this be optimized by doing [*~ -1] --> [+ 1] only once and feeding that result into the 4 rpoles? Bc it looks to me like they all get the same signal input.

True! Nice catch

Fixed version 4plop~.pd

with some other minor improvements as well: Resonance/cutoff compensation and anaclip are back in the mix