Re: [PD] [vcf~] with resonance?

2018-04-25 Thread Martin Peach 
On Wed, Apr 25, 2018 at 12:46 PM, William Huston 
wrote:

> Yes, thanks for the detailed response, Ed!
>
> I was hoping for some guidance for a bolt-on method for adding resonance
> to vcf~,
> but maybe it's not so easy? or the wrong approach?
>
> My error was thinking resonance was implemented with feedback.
>
> I don't think you were wrong.


> From this video, it looks like resonance is caused by a bump in the filter
> shape at the cutoff frequency:
> https://youtu.be/XA_WnyA7D6k
>
> The bump in the filter response is a manifestation of resonance caused by
feedback (the electronotes paper explains it as moving the poles toward the
imaginary axis as feedback increases).

An analog-synth-like filter can be made with 4 [lop~]s in series with a
[send~] at the output and a
[receive~]
|
[*~ -0.9]  <-change this number to set resonance (between 0 and -1)
|
[clip~ -1 1] <- stops it from blowing up, but gives distortion with too
much feedback
|
on the input. The main problem is that the resonance value changes with
filter cutoff frequency. Also Pd's number boxes don't have fine enough
resolution; I use negative values from 0-2 then divide by 1 to get
better control.

Martin
#N canvas 306 47 732 597 10;
#X obj 231 231 lop~ 440;
#X obj 231 274 lop~ 440;
#X obj 231 311 lop~ 440;
#X obj 231 351 lop~ 440;
#X obj 231 417 dac~;
#X obj 308 349 hsl 128 15 0 127 0 1 empty empty empty -2 -8 0 10 -4034
-1 -1 7700 1;
#X obj 305 373 / 128;
#X obj 230 388 *~;
#X obj 133 74 r~ \$0-fb;
#X obj 136 437 s~ \$0-fb;
#X obj 133 101 *~ -1;
#X obj 231 171 noise~;
#X obj 285 163 hsl 128 15 0 127 0 1 empty empty empty -2 -8 0 10 -4034
-1 -1 2300 1;
#X obj 282 187 / 128;
#X obj 232 204 *~;
#X obj 133 128 clip~ -1 1;
#X obj 197 84 / 1;
#X obj 338 217 nbx 7 14 -1e+037 1e+037 0 1 empty empty empty 0 -8 0
10 -4034 -1 -1 229 256;
#X obj 197 54 nbx 7 14 -2 0 0 1 empty empty empty 0 -8 0 10 -4034
-1 -1 -16960 256;
#X obj 103 221 vsl 15 128 0 100 0 0 empty empty empty 0 -9 0 10 -260097
-1 -1 12549 1;
#X obj 103 194 env~ 64;
#X connect 0 0 1 0;
#X connect 1 0 2 0;
#X connect 2 0 3 0;
#X connect 3 0 7 0;
#X connect 3 0 9 0;
#X connect 5 0 6 0;
#X connect 6 0 7 1;
#X connect 7 0 4 0;
#X connect 7 0 4 1;
#X connect 8 0 10 0;
#X connect 10 0 15 0;
#X connect 11 0 14 0;
#X connect 12 0 13 0;
#X connect 13 0 14 1;
#X connect 14 0 0 0;
#X connect 15 0 0 0;
#X connect 15 0 20 0;
#X connect 16 0 10 1;
#X connect 17 0 0 1;
#X connect 17 0 1 1;
#X connect 17 0 2 1;
#X connect 17 0 3 1;
#X connect 18 0 16 0;
#X connect 20 0 19 0;
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Re: [PD] [vcf~] with resonance?

2018-04-25 Thread Alexandre Torres Porres 
Q refers to the bandwidth of a resonant filter, but is ultimate effect t
depends on what kind of filter we're talking about. In some filters,
adjusting the bandwidth also boost the resonant frequency. This is not the
case of vcf~, which acts more like a constant gain bandpass filter. It's
more common in electronic music to have a lowpass resonant filter, though,
like the bob~ object, which emulates a moog filter.

So if you wanna make [vcf~] to have a higher boost in the resonant
frequency, just add some gain to it...

The [svf~] object has such kind of lowpass resonant filters. Cyclone also
has other filters, [lores~] is also a lowpass resonant filter, but it
frequency response varies with frequency (which I think is bad). Now, [reson~]
is a bandpass filter where you can adjust the bandwidth and overall gain. A
new couple of objects in cyclone are [filtercoeff~] and [biquad~], which
allow you to have a more proper lowpass resonant filter, controlled via
signals.

I actually think the   [filtercoeff~] + [biquad~] design is terrible. It'd
be much simpler just to have ready made filters. So I made them in mey new
library, for instance: [else/lowpass~].

cheers
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Re: [PD] [vcf~] with resonance?

2018-04-25 Thread Alexandre Torres Porres 
2018-04-25 15:03 GMT-03:00 William Huston :

> Thanks Christof.
>
> The help file for [svf~] shows a control-rate number box feeding the
> cutoff.
> But I tested with [sig~] and it works. Thanks.
>

the documentation (at least the current one) specifies all kinds of data
each inlets receives, and it says it takes floats/signals in every inlet.


>
> However I see no mention in the help of [scf~] for how to set Q.
>

the documentation (again, the current one) for cyclone/svf~ tells you the
Q/resonance is set via the 3rd inlet
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Re: [PD] [vcf~] with resonance?

2018-04-25 Thread William Huston 
Thanks Christof.

The help file for [svf~] shows a control-rate number box feeding the cutoff.
But I tested with [sig~] and it works. Thanks.

However I see no mention in the help of [scf~] for how to set Q.
Cutoff and Resonance only.

--
William Huston:  williamahus...@gmail.com
Binghamton NY

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On Wed, Apr 25, 2018 at 1:38 PM, Christof Ressi <christof.re...@gmx.at>
wrote:

> Hi William,
>
> both [vcf~] and [svf~] let you set the cutoff frequency at audio rate and
> both have adjustable Q... what are you missing exactly?
>
> the vcf_* filters in iemlib are all suited for audio rate modulations.
>
> for moog style lowpass filters have a look at [bob~] and [ggee/moog~].
>
> Christof
>
>
>
> Gesendet: Mittwoch, 25. April 2018 um 18:46 Uhr
> Von: "William Huston" <williamahus...@gmail.com>
> An: "Julian Brooks" <jbee...@gmail.com>
> Cc: "pd-list@lists.iem.at" <pd-list@lists.iem.at>
> Betreff: Re: [PD] [vcf~] with resonance?
>
> Yes, thanks for the detailed response, Ed!
>
> I was hoping for some guidance for a bolt-on method for adding resonance
> to vcf~,
> but maybe it's not so easy? or the wrong approach?
>
> My error was thinking resonance was implemented with feedback.
>
> From this video, it looks like resonance is caused by a bump in the filter
> shape at the cutoff frequency:
>
> https://youtu.be/XA_WnyA7D6k
>
> This looks like a shape that naturally occurs in analogue circuits.
> Someone in the FB group suggested [svf~] from Cyclone.
> It's really great, as it gives you HiP, LoP, BP, and Band Reject(!!).
>
> I would be in Filter Heaven if that had adjustable Q...
>
> PS: Can someone remind me of the filters where you can set parameters like
> cutoff freq at *audio rate*?
>
> Thanks!
> BH
>
>
>
>
> On Wed, Apr 25, 2018, 11:09 AM Julian Brooks <jbee...@gmail.com[mailto:
> jbee...@gmail.com]> wrote:
> Well, regardless of the correct number of inversions, some informative and
> well linked posts there - cheers for that Ed :)
>
> On 24 April 2018 at 20:44, Ed Kelly via Pd-list <pd-list@lists.iem.at
> [mailto:pd-list@lists.iem.at]> wrote:
>
> The 4-pole model in the ENS-85 paper does not have inversion at the input,
> but the Thomas Henry 2-pole design does. So I guess the 4-pole is more
> similar to vcf~
>
> go figure.
> Signing off
> Ed
>
>
> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>
> For Lone Shark releases, Pure Data software and published Research, go to
> http://sharktracks.co.uk[http://sharktracks.co.uk]
>
>
>
>
> On Tuesday, 24 April 2018, 14:40:20 GMT+1, Ed Kelly via Pd-list <
> pd-list@lists.iem.at[mailto:pd-list@lists.iem.at]> wrote:
>
>
>
> Ach! NO! inversion does not happen at the input!
> I guess you can look at the topologies and discover for yourself.
>
> I'm having a bad week.
> x
> Ed
>
>
> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>
> For Lone Shark releases, Pure Data software and published Research, go to
> http://sharktracks.co.uk[http://sharktracks.co.uk]
>
>
>
> On Tuesday, 24 April 2018, 14:33:13 GMT+1, Ed Kelly <
> morph_2...@yahoo.co.uk[mailto:morph_2...@yahoo.co.uk]> wrote:
>
>
>
> Correct me if I'm wrong (and I'm sure someone will) but going back to
> analog electronics...
>
> If you examine the topology of a standard analog filter design, such as
> the Thomas Henry VCF1 (http://www.birthofasynth.com/
> Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf[http://www.birthofasynth.com/Thomas_
> Henry/pdf/VCF-1/Sheet_0002.pdf]) you will see that the signal path from
> input to output goes through 5 inversion stages before being fed back into
> the input to generate resonance. Therefore it is inverted.
>
>
> Since most (resonant) filters consist of an even number of stages (and
> therefore an even number of poles and/or zeroes) you should probably invert
> the feedback. With an odd number you should probably not invert feedback.
> My guess is that vcf~ implements an even-number (probably 4-pole) resonant
> filter, a la Moog. You can also try mvcf~ from my library (ekext -
> http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz[
> http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz]) which is another
>

Re: [PD] [vcf~] with resonance?

2018-04-25 Thread Christof Ressi 
Hi William,

both [vcf~] and [svf~] let you set the cutoff frequency at audio rate and both 
have adjustable Q... what are you missing exactly? 

the vcf_* filters in iemlib are all suited for audio rate modulations.

for moog style lowpass filters have a look at [bob~] and [ggee/moog~]. 

Christof
 
 

Gesendet: Mittwoch, 25. April 2018 um 18:46 Uhr
Von: "William Huston" <williamahus...@gmail.com>
An: "Julian Brooks" <jbee...@gmail.com>
Cc: "pd-list@lists.iem.at" <pd-list@lists.iem.at>
Betreff: Re: [PD] [vcf~] with resonance?

Yes, thanks for the detailed response, Ed!
 
I was hoping for some guidance for a bolt-on method for adding resonance to 
vcf~,
but maybe it's not so easy? or the wrong approach?
 
My error was thinking resonance was implemented with feedback.
 
From this video, it looks like resonance is caused by a bump in the filter 
shape at the cutoff frequency:
 
https://youtu.be/XA_WnyA7D6k
 
This looks like a shape that naturally occurs in analogue circuits. 
Someone in the FB group suggested [svf~] from Cyclone.
It's really great, as it gives you HiP, LoP, BP, and Band Reject(!!).
 
I would be in Filter Heaven if that had adjustable Q...
 
PS: Can someone remind me of the filters where you can set parameters like 
cutoff freq at *audio rate*?
 
Thanks!
BH
 
 
 

On Wed, Apr 25, 2018, 11:09 AM Julian Brooks 
<jbee...@gmail.com[mailto:jbee...@gmail.com]> wrote:
Well, regardless of the correct number of inversions, some informative and well 
linked posts there - cheers for that Ed :)
 
On 24 April 2018 at 20:44, Ed Kelly via Pd-list 
<pd-list@lists.iem.at[mailto:pd-list@lists.iem.at]> wrote:

The 4-pole model in the ENS-85 paper does not have inversion at the input, but 
the Thomas Henry 2-pole design does. So I guess the 4-pole is more similar to 
vcf~
 
go figure.
Signing off
Ed
 
 
_-_-_-_-_-_-_-^-_-_-_-_-_-_-_

For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk[http://sharktracks.co.uk] 

 
 

On Tuesday, 24 April 2018, 14:40:20 GMT+1, Ed Kelly via Pd-list 
<pd-list@lists.iem.at[mailto:pd-list@lists.iem.at]> wrote:
 
 

Ach! NO! inversion does not happen at the input!
I guess you can look at the topologies and discover for yourself.
 
I'm having a bad week.
x
Ed
 
 
_-_-_-_-_-_-_-^-_-_-_-_-_-_-_

For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk[http://sharktracks.co.uk] 
 
 

On Tuesday, 24 April 2018, 14:33:13 GMT+1, Ed Kelly 
<morph_2...@yahoo.co.uk[mailto:morph_2...@yahoo.co.uk]> wrote:
 
 

Correct me if I'm wrong (and I'm sure someone will) but going back to analog 
electronics...
 
If you examine the topology of a standard analog filter design, such as the 
Thomas Henry VCF1 
(http://www.birthofasynth.com/Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf[http://www.birthofasynth.com/Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf])
 you will see that the signal path from input to output goes through 5 
inversion stages before being fed back into the input to generate resonance. 
Therefore it is inverted.
 

Since most (resonant) filters consist of an even number of stages (and 
therefore an even number of poles and/or zeroes) you should probably invert the 
feedback. With an odd number you should probably not invert feedback. My guess 
is that vcf~ implements an even-number (probably 4-pole) resonant filter, a la 
Moog. You can also try mvcf~ from my library (ekext - 
http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz[http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz])
 which is another attempt at emulating this topology, or there are lots of 
others I'm sure you know about.
This might seem counter-intuitive, but the image below shows how this works 
with regards to vcf~ - the output of vcf~ is NOT inverted, whereas the output 
of an analog VCF should be.
Odd-number staged filters are very rare in the analog world, and most (i.e. 
18dB per octave) were created to implement the (mythical 3-pole topology) 
filter of the Roland TB303. However, according to the schematics of the TB303 
it is a four-pole diode-ladder VCF using transistors as diodes, with extra 
resonance artifacts revealed by Tim Stinchcombe on his excellent website. Tim 
Stinchcombe - TB-303 Diode Ladder Filter 
model[http://www.timstinchcombe.co.uk/index.php?pge=diode2]
 

 
Tim Stinchcombe - TB-303 Diode Ladder Filter 
model[http://www.timstinchcombe.co.uk/index.php?pge=diode2]

 

 
 
 
Meanwhile, if you want to go deeper with regards to 4-pole filter topologies 
(and lowpass/highpass configurations) it is worth checking out a paper 
published in 1985 - 
http://electronotes.netfirms.com/EN85VCF.PDF[http://electronotes.netfirms.com/EN85VCF.PDF]

 

The easiest way to think about it, from this paper, is that you think about 
each stage as an inversion, and the input itself is one of the stages, so for a 
4-pole filter there are 4+1 inversion stages. But in the dig

Re: [PD] [vcf~] with resonance?

2018-04-25 Thread William Huston 
Yes, thanks for the detailed response, Ed!

I was hoping for some guidance for a bolt-on method for adding resonance to
vcf~,
but maybe it's not so easy? or the wrong approach?

My error was thinking resonance was implemented with feedback.

>From this video, it looks like resonance is caused by a bump in the filter
shape at the cutoff frequency:
https://youtu.be/XA_WnyA7D6k

This looks like a shape that naturally occurs in analogue circuits.

Someone in the FB group suggested [svf~] from Cyclone.
It's really great, as it gives you HiP, LoP, BP, and Band Reject(!!).

I would be in Filter Heaven if that had adjustable Q...

PS: Can someone remind me of the filters where you can set parameters like
cutoff freq at *audio rate*?

Thanks!
BH



On Wed, Apr 25, 2018, 11:09 AM Julian Brooks  wrote:

> Well, regardless of the correct number of inversions, some informative and
> well linked posts there - cheers for that Ed :)
>
> On 24 April 2018 at 20:44, Ed Kelly via Pd-list 
> wrote:
>
>> The 4-pole model in the ENS-85 paper does not have inversion at the
>> input, but the Thomas Henry 2-pole design does. So I guess the 4-pole is
>> more similar to vcf~
>>
>> go figure.
>> Signing off
>> Ed
>>
>>
>> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>>
>> For *Lone Shark *releases, *Pure Data *software and published *Research*,
>> go to http://sharktracks.co.uk
>>
>>
>> On Tuesday, 24 April 2018, 14:40:20 GMT+1, Ed Kelly via Pd-list <
>> pd-list@lists.iem.at> wrote:
>>
>>
>> Ach! NO! inversion does not happen at the input!
>> I guess you can look at the topologies and discover for yourself.
>>
>> I'm having a bad week.
>> x
>> Ed
>>
>>
>> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>>
>> For *Lone Shark *releases, *Pure Data *software and published *Research*,
>> go to http://sharktracks.co.uk
>>
>>
>> On Tuesday, 24 April 2018, 14:33:13 GMT+1, Ed Kelly <
>> morph_2...@yahoo.co.uk> wrote:
>>
>>
>> Correct me if I'm wrong (and I'm sure someone will) but going back to
>> analog electronics...
>>
>> If you examine the topology of a standard analog filter design, such as
>> the Thomas Henry VCF1 (http://www.birthofasynth.com/
>> Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf) you will see that the signal path
>> from input to output goes through 5 inversion stages before being fed back
>> into the input to generate resonance. Therefore it is inverted.
>>
>> Since most (resonant) filters consist of an even number of stages (and
>> therefore an even number of poles and/or zeroes) you should probably invert
>> the feedback. With an odd number you should probably not invert feedback.
>> My guess is that vcf~ implements an even-number (probably 4-pole) resonant
>> filter, a la Moog. You can also try mvcf~ from my library (ekext -
>> http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz) which is another
>> attempt at emulating this topology, or there are lots of others I'm sure
>> you know about.
>>
>> This might seem counter-intuitive, but the image below shows how this
>> works with regards to vcf~ - the output of vcf~ is NOT inverted, whereas
>> the output of an analog VCF should be.
>>
>> Odd-number staged filters are very rare in the analog world, and most
>> (i.e. 18dB per octave) were created to implement the (mythical 3-pole
>> topology) filter of the Roland TB303. However, according to the schematics
>> of the TB303 it is a four-pole diode-ladder VCF using transistors as
>> diodes, with extra resonance artifacts revealed by Tim Stinchcombe on his
>> excellent website. Tim Stinchcombe - TB-303 Diode Ladder Filter model
>> 
>>
>> Tim Stinchcombe - TB-303 Diode Ladder Filter model
>>
>> 
>>
>>
>>
>> Meanwhile, if you want to go deeper with regards to 4-pole filter
>> topologies (and lowpass/highpass configurations) it is worth checking out a
>> paper published in 1985 - http://electronotes.netfirms.com/EN85VCF.PDF
>>
>> The easiest way to think about it, from this paper, is that you think
>> about each stage as an inversion, and the input itself is one of the
>> stages, so for a 4-pole filter there are 4+1 inversion stages. But in the
>> digital world I guess you'll have to test input and output at a relatively
>> low frequency to the cutoff to determine inversion principles for the
>> enhancement of resonance.
>>
>> I hope this helps. It gave me a break from mixing!
>> Ed
>> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>>
>> For *Lone Shark *releases, *Pure Data *software and published *Research*,
>> go to http://sharktracks.co.uk
>>
>>
>> On Tuesday, 24 April 2018, 06:44:19 GMT+1, William Huston <
>> williamahus...@gmail.com> wrote:
>>
>>
>> What's the best or "correct" way to add resonance to a [vcf~]?
>>
>>- Should the feedback be delayed?
>>- Should the feedback be inverted?
>>- Should the feedback be from the outlet I'm using?
>>   - Or should the feedback always come from the BP or HiPass side?
>>
>>

Re: [PD] [vcf~] with resonance?

2018-04-25 Thread Julian Brooks 
Well, regardless of the correct number of inversions, some informative and
well linked posts there - cheers for that Ed :)

On 24 April 2018 at 20:44, Ed Kelly via Pd-list 
wrote:

> The 4-pole model in the ENS-85 paper does not have inversion at the input,
> but the Thomas Henry 2-pole design does. So I guess the 4-pole is more
> similar to vcf~
>
> go figure.
> Signing off
> Ed
>
>
> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>
> For *Lone Shark *releases, *Pure Data *software and published *Research*,
> go to http://sharktracks.co.uk
>
>
> On Tuesday, 24 April 2018, 14:40:20 GMT+1, Ed Kelly via Pd-list <
> pd-list@lists.iem.at> wrote:
>
>
> Ach! NO! inversion does not happen at the input!
> I guess you can look at the topologies and discover for yourself.
>
> I'm having a bad week.
> x
> Ed
>
>
> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>
> For *Lone Shark *releases, *Pure Data *software and published *Research*,
> go to http://sharktracks.co.uk
>
>
> On Tuesday, 24 April 2018, 14:33:13 GMT+1, Ed Kelly <
> morph_2...@yahoo.co.uk> wrote:
>
>
> Correct me if I'm wrong (and I'm sure someone will) but going back to
> analog electronics...
>
> If you examine the topology of a standard analog filter design, such as
> the Thomas Henry VCF1 (http://www.birthofasynth.com/
> Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf) you will see that the signal path
> from input to output goes through 5 inversion stages before being fed back
> into the input to generate resonance. Therefore it is inverted.
>
> Since most (resonant) filters consist of an even number of stages (and
> therefore an even number of poles and/or zeroes) you should probably invert
> the feedback. With an odd number you should probably not invert feedback.
> My guess is that vcf~ implements an even-number (probably 4-pole) resonant
> filter, a la Moog. You can also try mvcf~ from my library (ekext -
> http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz) which is another
> attempt at emulating this topology, or there are lots of others I'm sure
> you know about.
>
> This might seem counter-intuitive, but the image below shows how this
> works with regards to vcf~ - the output of vcf~ is NOT inverted, whereas
> the output of an analog VCF should be.
>
> Odd-number staged filters are very rare in the analog world, and most
> (i.e. 18dB per octave) were created to implement the (mythical 3-pole
> topology) filter of the Roland TB303. However, according to the schematics
> of the TB303 it is a four-pole diode-ladder VCF using transistors as
> diodes, with extra resonance artifacts revealed by Tim Stinchcombe on his
> excellent website. Tim Stinchcombe - TB-303 Diode Ladder Filter model
> 
>
> Tim Stinchcombe - TB-303 Diode Ladder Filter model
>
> 
>
>
>
> Meanwhile, if you want to go deeper with regards to 4-pole filter
> topologies (and lowpass/highpass configurations) it is worth checking out a
> paper published in 1985 - http://electronotes.netfirms.com/EN85VCF.PDF
>
> The easiest way to think about it, from this paper, is that you think
> about each stage as an inversion, and the input itself is one of the
> stages, so for a 4-pole filter there are 4+1 inversion stages. But in the
> digital world I guess you'll have to test input and output at a relatively
> low frequency to the cutoff to determine inversion principles for the
> enhancement of resonance.
>
> I hope this helps. It gave me a break from mixing!
> Ed
> _-_-_-_-_-_-_-^-_-_-_-_-_-_-_
>
> For *Lone Shark *releases, *Pure Data *software and published *Research*,
> go to http://sharktracks.co.uk
>
>
> On Tuesday, 24 April 2018, 06:44:19 GMT+1, William Huston <
> williamahus...@gmail.com> wrote:
>
>
> What's the best or "correct" way to add resonance to a [vcf~]?
>
>- Should the feedback be delayed?
>- Should the feedback be inverted?
>- Should the feedback be from the outlet I'm using?
>   - Or should the feedback always come from the BP or HiPass side?
>
> Thanks!
> BH
>
> --
> William Huston:  williamahus...@gmail.com
> Binghamton NY
>
> *Public Service Mapping / Videography / Research*
> Blog  -- Facebook
>  -- Twitter
> -- Youtube
> 
> Document collections: VirtualPipelines
>  -- BHDCSDimockArchive
> 
> Please support my work: TinyURL.com/DonateToBillHuston
>
>
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> Pd-list@lists.iem.at mailing list
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Re: [PD] [vcf~] with resonance?

2018-04-24 Thread Ed Kelly via Pd-list 
The 4-pole model in the ENS-85 paper does not have inversion at the input, but 
the Thomas Henry 2-pole design does. So I guess the 4-pole is more similar to 
vcf~

go figure.
Signing off
Ed


_-_-_-_-_-_-_-^-_-_-_-_-_-_-_

For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk  

On Tuesday, 24 April 2018, 14:40:20 GMT+1, Ed Kelly via Pd-list 
 wrote:  
 
 Ach! NO! inversion does not happen at the input!
I guess you can look at the topologies and discover for yourself.

I'm having a bad week.
x
Ed
 

_-_-_-_-_-_-_-^-_-_-_-_-_-_-_

For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk  

On Tuesday, 24 April 2018, 14:33:13 GMT+1, Ed Kelly 
 wrote:  
 
 Correct me if I'm wrong (and I'm sure someone will) but going back to analog 
electronics...
If you examine the topology of a standard analog filter design, such as the 
Thomas Henry VCF1 
(http://www.birthofasynth.com/Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf) you will 
see that the signal path from input to output goes through 5 inversion stages 
before being fed back into the input to generate resonance. Therefore it is 
inverted.

Since most (resonant) filters consist of an even number of stages (and 
therefore an even number of poles and/or zeroes) you should probably invert the 
feedback. With an odd number you should probably not invert feedback. My guess 
is that vcf~ implements an even-number (probably 4-pole) resonant filter, a la 
Moog. You can also try mvcf~ from my library (ekext - 
http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz) which is another attempt 
at emulating this topology, or there are lots of others I'm sure you know about.

This might seem counter-intuitive, but the image below shows how this works 
with regards to vcf~ - the output of vcf~ is NOT inverted, whereas the output 
of an analog VCF should be.

Odd-number staged filters are very rare in the analog world, and most (i.e. 
18dB per octave) were created to implement the (mythical 3-pole topology) 
filter of the Roland TB303. However, according to the schematics of the TB303 
it is a four-pole diode-ladder VCF using transistors as diodes, with extra 
resonance artifacts revealed by Tim Stinchcombe on his excellent website. Tim 
Stinchcombe - TB-303 Diode Ladder Filter model

| 
| 
|  | 
Tim Stinchcombe - TB-303 Diode Ladder Filter model


 |

 |

 |




Meanwhile, if you want to go deeper with regards to 4-pole filter topologies 
(and lowpass/highpass configurations) it is worth checking out a paper 
published in 1985 - http://electronotes.netfirms.com/EN85VCF.PDF
The easiest way to think about it, from this paper, is that you think about 
each stage as an inversion, and the input itself is one of the stages, so for a 
4-pole filter there are 4+1 inversion stages. But in the digital world I guess 
you'll have to test input and output at a relatively low frequency to the 
cutoff to determine inversion principles for the enhancement of resonance.

I hope this helps. It gave me a break from mixing!
Ed
_-_-_-_-_-_-_-^-_-_-_-_-_-_-_
For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk  

On Tuesday, 24 April 2018, 06:44:19 GMT+1, William Huston 
 wrote:  
 
 What's the best or "correct" way to add resonance to a [vcf~]? 
   
   - Should the feedback be delayed?
   - Should the feedback be inverted? 
   - Should the feedback be from the outlet I'm using?
   
   - Or should the feedback always come from the BP or HiPass side?
Thanks!BH

--
William Huston:  williamahus...@gmail.com
Binghamton NY

Public Service Mapping / Videography / Research
Blog -- Facebook -- Twitter  -- Youtube
Document collections: VirtualPipelines -- BHDCSDimockArchive
Please support my work: TinyURL.com/DonateToBillHuston


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Re: [PD] [vcf~] with resonance?

2018-04-24 Thread Ed Kelly via Pd-list 
Ach! NO! inversion does not happen at the input!
I guess you can look at the topologies and discover for yourself.

I'm having a bad week.
x
Ed
 

_-_-_-_-_-_-_-^-_-_-_-_-_-_-_

For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk  

On Tuesday, 24 April 2018, 14:33:13 GMT+1, Ed Kelly 
 wrote:  
 
 Correct me if I'm wrong (and I'm sure someone will) but going back to analog 
electronics...
If you examine the topology of a standard analog filter design, such as the 
Thomas Henry VCF1 
(http://www.birthofasynth.com/Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf) you will 
see that the signal path from input to output goes through 5 inversion stages 
before being fed back into the input to generate resonance. Therefore it is 
inverted.

Since most (resonant) filters consist of an even number of stages (and 
therefore an even number of poles and/or zeroes) you should probably invert the 
feedback. With an odd number you should probably not invert feedback. My guess 
is that vcf~ implements an even-number (probably 4-pole) resonant filter, a la 
Moog. You can also try mvcf~ from my library (ekext - 
http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz) which is another attempt 
at emulating this topology, or there are lots of others I'm sure you know about.

This might seem counter-intuitive, but the image below shows how this works 
with regards to vcf~ - the output of vcf~ is NOT inverted, whereas the output 
of an analog VCF should be.

Odd-number staged filters are very rare in the analog world, and most (i.e. 
18dB per octave) were created to implement the (mythical 3-pole topology) 
filter of the Roland TB303. However, according to the schematics of the TB303 
it is a four-pole diode-ladder VCF using transistors as diodes, with extra 
resonance artifacts revealed by Tim Stinchcombe on his excellent website. Tim 
Stinchcombe - TB-303 Diode Ladder Filter model

| 
| 
|  | 
Tim Stinchcombe - TB-303 Diode Ladder Filter model


 |

 |

 |




Meanwhile, if you want to go deeper with regards to 4-pole filter topologies 
(and lowpass/highpass configurations) it is worth checking out a paper 
published in 1985 - http://electronotes.netfirms.com/EN85VCF.PDF
The easiest way to think about it, from this paper, is that you think about 
each stage as an inversion, and the input itself is one of the stages, so for a 
4-pole filter there are 4+1 inversion stages. But in the digital world I guess 
you'll have to test input and output at a relatively low frequency to the 
cutoff to determine inversion principles for the enhancement of resonance.

I hope this helps. It gave me a break from mixing!
Ed
_-_-_-_-_-_-_-^-_-_-_-_-_-_-_
For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk  

On Tuesday, 24 April 2018, 06:44:19 GMT+1, William Huston 
 wrote:  
 
 What's the best or "correct" way to add resonance to a [vcf~]? 
   
   - Should the feedback be delayed?
   - Should the feedback be inverted? 
   - Should the feedback be from the outlet I'm using?
   
   - Or should the feedback always come from the BP or HiPass side?
Thanks!BH

--
William Huston:  williamahus...@gmail.com
Binghamton NY

Public Service Mapping / Videography / Research
Blog -- Facebook -- Twitter  -- Youtube
Document collections: VirtualPipelines -- BHDCSDimockArchive
Please support my work: TinyURL.com/DonateToBillHuston


___
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Re: [PD] [vcf~] with resonance?

2018-04-24 Thread Ed Kelly via Pd-list 
Correct me if I'm wrong (and I'm sure someone will) but going back to analog 
electronics...
If you examine the topology of a standard analog filter design, such as the 
Thomas Henry VCF1 
(http://www.birthofasynth.com/Thomas_Henry/pdf/VCF-1/Sheet_0002.pdf) you will 
see that the signal path from input to output goes through 5 inversion stages 
before being fed back into the input to generate resonance. Therefore it is 
inverted.

Since most (resonant) filters consist of an even number of stages (and 
therefore an even number of poles and/or zeroes) you should probably invert the 
feedback. With an odd number you should probably not invert feedback. My guess 
is that vcf~ implements an even-number (probably 4-pole) resonant filter, a la 
Moog. You can also try mvcf~ from my library (ekext - 
http://sharktracks.co.uk/puredata/ekext-0.1.8.tar.gz) which is another attempt 
at emulating this topology, or there are lots of others I'm sure you know about.

This might seem counter-intuitive, but the image below shows how this works 
with regards to vcf~ - the output of vcf~ is NOT inverted, whereas the output 
of an analog VCF should be.

Odd-number staged filters are very rare in the analog world, and most (i.e. 
18dB per octave) were created to implement the (mythical 3-pole topology) 
filter of the Roland TB303. However, according to the schematics of the TB303 
it is a four-pole diode-ladder VCF using transistors as diodes, with extra 
resonance artifacts revealed by Tim Stinchcombe on his excellent website. Tim 
Stinchcombe - TB-303 Diode Ladder Filter model

| 
| 
|  | 
Tim Stinchcombe - TB-303 Diode Ladder Filter model


 |

 |

 |




Meanwhile, if you want to go deeper with regards to 4-pole filter topologies 
(and lowpass/highpass configurations) it is worth checking out a paper 
published in 1985 - http://electronotes.netfirms.com/EN85VCF.PDF
The easiest way to think about it, from this paper, is that you think about 
each stage as an inversion, and the input itself is one of the stages, so for a 
4-pole filter there are 4+1 inversion stages. But in the digital world I guess 
you'll have to test input and output at a relatively low frequency to the 
cutoff to determine inversion principles for the enhancement of resonance.

I hope this helps. It gave me a break from mixing!
Ed
_-_-_-_-_-_-_-^-_-_-_-_-_-_-_
For Lone Shark releases, Pure Data software and published Research, go to 
http://sharktracks.co.uk  

On Tuesday, 24 April 2018, 06:44:19 GMT+1, William Huston 
 wrote:  
 
 What's the best or "correct" way to add resonance to a [vcf~]? 
   
   - Should the feedback be delayed?
   - Should the feedback be inverted? 
   - Should the feedback be from the outlet I'm using?
   
   - Or should the feedback always come from the BP or HiPass side?
Thanks!BH

--
William Huston:  williamahus...@gmail.com
Binghamton NY

Public Service Mapping / Videography / Research
Blog -- Facebook -- Twitter  -- Youtube
Document collections: VirtualPipelines -- BHDCSDimockArchive
Please support my work: TinyURL.com/DonateToBillHuston


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[PD] [vcf~] with resonance?

2018-04-23 Thread William Huston 
What's the best or "correct" way to add resonance to a [vcf~]?

   - Should the feedback be delayed?
   - Should the feedback be inverted?
   - Should the feedback be from the outlet I'm using?
  - Or should the feedback always come from the BP or HiPass side?

Thanks!
BH

--
William Huston:  williamahus...@gmail.com
Binghamton NY

*Public Service Mapping / Videography / Research*
Blog  -- Facebook
 -- Twitter
-- Youtube

Document collections: VirtualPipelines 
-- BHDCSDimockArchive 
Please support my work: TinyURL.com/DonateToBillHuston
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