Filter design

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Warp69
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Filter design

Post by Warp69 »

Hi,

Here's a little test of 2 different lowpass filter designs - which one is the best implementation regarding low frequency response etc.? Please modulate the parameters all you can.

Unfortunately the C1 & C2 are not calibrated - so they wont match - that will of course make the test abit more difficult.

C1 = C2 = Range [0 ; MAX]

http://www.relab.dk/Filter.rar (new upload - should be easier to follow)

Cheers
Last edited by Warp69 on Sat Dec 27, 2008 6:52 am, edited 1 time in total.
dawman
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Re: Filter design

Post by dawman »

Thanks Martin.
Warp69
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Re: Filter design

Post by Warp69 »

Im not sure for what :-?

I think this is only usable in Scope SDK - It's not a device, but only a test of different filter topologies - sorry.
dawman
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Re: Filter design

Post by dawman »

Well I just found that out.
I tried to load it as an insert in Prowave................No Bueno.
So I then loaded it into the project window and ran my analog synth through it, at a very degraded signal. :lol:
I should have known when it had no GUI that something was wrong.

Anyway Thanks for building and developing for Scope SDK then.

Happy New Year.
Warp69
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Re: Filter design

Post by Warp69 »

New upload - should be easier to follow.
tgstgs
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Re: Filter design

Post by tgstgs »

noone responding here?

is there a reason for sync controles?
do you want to modulate?
---------

for low frequency these are about the same to my ears;
havent checked if theres a difference in circles;


LP2

i wouldnt use for audio;
but it has its existance for analysing;
thatfor i would use async singal for controlling to save a lot of circles;


LP1

sounds better to my ears in the high frequency range;
only probl. is the recursive tap itself:
at max should be a cutoff Samplerate/2 but is not! its a bit lower;
this is like the stock atoms filters and was the reason for my personalstudy;
youre able to solve this by lowering C2 from last add (mix3) when the max controll is reached;
but im sure you know!!

so to your question:
LP1 is better the higher the cutoff is;
with the probl. of the last few HZ up to SR/2 where i would prever LP2 aproach;

good vibes from vienna
Warp69
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Re: Filter design

Post by Warp69 »

Hi tgstgs,

Thats correct - the sync module is for modulation purpose.

I have uploaded yet another version - now including the Chamberlin form (LP3) - http://www.relab.dk/Filter.rar

The LP1 form is a low sensitive structure - better response than LP2 with modulation.

Not many are apparently interested in filter structures
tgstgs
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Re: Filter design

Post by tgstgs »

had lots of fun with matlab;
check it out;

porting c to sdk i was not able to beat stock atoms circles;
need to build in assembler;

im sure with xite a lot of high order exotic filters are possible
time will tell . .
----------


will test lp3 later

good vibes
sonolive
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Re: Filter design

Post by sonolive »

hi all,
Not many are apparently interested in filter structures
noone responding here?
actually an intereting subject ... i follow it as possible ... and maybe will post , but miss time,

let me just say that DSP Equing/filtering is a wonderfull world, full of maths and passionating things (truncations, approximations, nodes overloads ...)

we at DAS have spent 6 months to realise our master it eq algo,

Martin thx again for your contribution to our knowledge ;-)

cheerz
olive
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Shroomz~>
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Re: Filter design

Post by Shroomz~> »

Hi Martin, we're just back from spending xmas with family. I'll check out your filters as soon as I can get access to the sdk, but I'm not quite sure when that will be...

cheers,
Mark
sonolive
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Re: Filter design

Post by sonolive »

hi martin,
i had a look this afternoon at your designs , actually interesting , espacially the LP3, many possibilities as "musical" filter ...

there are some things i don't understand ... Mix 3 instead of Mix 2 (that would make the dev lighter ... (dsp consuption speaking, ) but i guess you have something else in mind !

LP3, "sounds" great ... i didn't know this implementation, quite versatile and really "optimisable" ...

in term of "strict low pass", i would prefer LP2, but at this time i must admit that i didn't passed audio throu it, only "fft analisys" ... and i do know by experience that it is not a good judge ...

i am still really interesed in your further researches ...

cheerz
olive
Warp69
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Re: Filter design

Post by Warp69 »

Sorry the Mix3 modules could easily be replaced with Mix2 - they were used to correct the summing issue of positive numbers - but that should be handle differently because of negative numbers.

The filter structures are without saturation and randomization - that should be implemented somewhere in the feedback loops for different effects.

I'll wait before I release additional structures - some could also cascade 4 LP1 with feedbacks - ladder type filters.

Oh and the sync modules is only for audiorate modulation.

Cheers
tgstgs
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Re: Filter design

Post by tgstgs »

sorry for late reply

last download here in topic LP3 is oszilating;
= not stabil;

im hear a fu* ringing with low input at about -12dB _ NO???


good vibes
Warp69
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Re: Filter design

Post by Warp69 »

tgstgs wrote:LP3 is oszilating;
Only at MAX res
tgstgs
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Re: Filter design

Post by tgstgs »

have to agree with olive LP3 sounds very good;
i tested with a guitar doing sort of wah effect with a controller;
specialy on low frequency input i like what it does to the higher parts of the guitar spectrum;
----
this is definitive worth further development;
have to test its switching characteristics;
need some time

good vibes
MCCY
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Re: Filter design

Post by MCCY »

I am very interested in taking a look into those structures, but didn't find the time so far. I bet I missed something, I guess I will not understand anything though :-). Thanks anyway, I'll comment when I find the time for testing.

1000 Thanks, exspecially for your old topic on reverbs too!!! It's so cool to have people here sharing knowledge on such a high level.

Martin II
Warp69
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Re: Filter design

Post by Warp69 »

Well - after this success and awesome participation its about time to continue.

I hope most people looking at the structure found out how to extract highpass and bandpass simultaneously from Filter3 - otherwise you can download it here : www.relab.dk/Filters.mdl

If you sum the LP3 and the HP3 you get band reject.
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Shroomz~>
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Re: Filter design

Post by Shroomz~> »

Thanks, I'd like to get involved in this discussion when I've got some free time with the sdk again.
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hifiboom
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Re: Filter design

Post by hifiboom »

warp, do you know how you can build oversampling filters via sdk?

i ve not yet found a way, surely by touching the assembly code, but with the basic atoms?
Warp69
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Re: Filter design

Post by Warp69 »

Not by basic SDK atoms.

I do have access to STW oversampling modules.

I talked with Jurgen at the Musik Messe regarding oversampling modules for the XITE system - Sonic Core will look into it - the modules will have additional in/outputs for oversampling - 2 in/outputs for 2x oversampling and 4 in/outputs for 4x oversampling.
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