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 Forum index » Instruments and Equipment » Modular Synthesis
How Do You Use Filters?
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JovianPyx



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PostPosted: Thu Jun 07, 2018 12:58 pm    Post subject: How Do You Use Filters? Reply with quote  Mark this post and the followings unread

I'm interested in how modular users apply filters to a patch.

Do you chain filters together to get unique responses?

If you do, how complex are the combinations of filters?

And what sort of interconnections do you find most useful?

Given that you had more than enough filters, how many filters would be sufficient to meet your needs?

Thank you for your time and input.

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Blue Hell
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PostPosted: Thu Jun 07, 2018 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Okay ... some random filter thoughts from me ...

a filter should go very low .. sub Hz, to filter conntrol voltages ... for example .. make a glide with some reso on an input voltage jump .. SVF can do it.

For filter seeps of course, but the its nice when the filter has some distortion.

Linear FM is nice to have for a more pleasant wobble.

But erm .. waveform mangling usually is nicer than filtering (oscillator linear FM feedback .. or shape modulation) .. although I do use a 6 dB filter sometimes in the feedback path for this to make it less noise like on high feedback.

Then filter banks ... I limited myself to 11 frequencies .. but something like eight can do some nice modal stuff already (bells and such).

6 dB filters are more useful to me than 24 dB ones .. I almost never use 24 dB

a 6dB very low frequency filter is nice to have for glides.

A tilt filter is a nice thing too ... slope variable from -6 dB to + 6 dB with a controllable rotation point .. for coloring things down mostly, but up as well occasionally.

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AlanP



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PostPosted: Thu Jun 07, 2018 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm fairly boring, I use different filters depending on what 'sound' I want. The Steiner-Parker is unforgiving, the ARP4072 sounds bubbly, and the Minimoog sounds smoov.

Where things get interesting can be the fixed filter bank, or resonant EQ. Feedback patches, comb outputs (sweeping a comb filter with a bandpass gets you interesting results!)

How broadly are you defining 'filter'?
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JovianPyx



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PostPosted: Thu Jun 07, 2018 1:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Filter meaning what I'd call the classical meaning such as ladder, svf, filters with resonance, filters with at least one pole, etc. Not wave shaping or wave mangling.

I was actually most interested in analog filters, but digital filters also apply I think since they generally do the same kinds of things. My interest is mostly in combinations of filters such as to produce shelf and other spectral profiles.

Filters like SVF that have mode outputs, as well as more simple filters like single pole RC high or low pass. How are they most usefully connected?

So the question is how rare is it to connect 2 or more filters together (in parallel or series)? Or is a filter most often used alone?

I understand about sweeps, probably the most used and most profound effect of a filter with a resonance peak in the spectral profile (two or more poles). I'm interested in the more unusual uses for filters.

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varice



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PostPosted: Fri Jun 08, 2018 4:02 am    Post subject: Reply with quote  Mark this post and the followings unread

I normally just use one type of filter in a patch along with some occasional parametric EQ, but I’ve had a lot of fun recently running a MicroBrute signal through its Steiner-Parker style filter into an ELTA Music Polivoks filter pedal. Both of those filters have a lot of unique character of their own. This series connection sure can allow for a large amount of tone tweaking… Cool
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g.gabba



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PostPosted: Fri Jun 08, 2018 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

ive read recently that a highpass filter in front of a TZVCO result in phase-modulation instead of frequenzy-modulation.
altough i did not understand why and how.
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JovianPyx



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PostPosted: Fri Jun 08, 2018 7:37 am    Post subject: Reply with quote  Mark this post and the followings unread

To be honest, I don't know the precise difference and I've read that FM is really PM anyway (at least in the digital domain since I've never done FM with analog methods). I suspect that they are simply different ways to say the same thing (again, digital domain). I've written digital code to do "FM" and honestly, because of how it's done, it does seem mathematically to be a modulation of phase because it never deals with full cycles of the waveform being modulated, but then I think this is true for analog as well.. It works by either advancing or retarding the phase change per sample time of the modulated waveform. In the end, when the run of phase changes are examined over several cycles of the modulated waveform, then it appears conceptually as frequency modulation. It reminds me of describing light as either a wave or a particle but not both at the same time.

So my question is then - how is the sound affected by changing from FM to PM (using a filter)? And I have to wonder whether there is actually a change from FM to PM or is the effect simply the filter's generally subtractive modification of the spectral quality of the sound with added perturbations from imperfections in an analog filter such as integrator or amplifier distortion. I'm seeing here that analog filters have a characteristic sounds per type so it appears that a filter (say in low pass mode) is not necessarily fully subtractive, but rather can add harmonics. This would make it difficult to point a finger at what a wave mangler (FM) is doing all by itself without the help of the filter.

I realize that didn't make anything any more clear... Confused Confused

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Blue Hell
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PostPosted: Fri Jun 08, 2018 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

A static phase difference can not be heard, a static frequency difference can.

When you have an FM input and high pass filter in front of it that's sort of like differentiating ... and in that lies the difference between FM and PM .. PM being FM with a differentiated signal (so you will hear changes in the CV but not the actual value).

In a digital osc for FM you change the amount to be added to the phase accu (on each sample) and for PM you change the phase accu directly (with an offset).

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JovianPyx



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PostPosted: Fri Jun 08, 2018 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, I still see no difference, but that's me.

What is the sonic difference between FM and PM? Are there examples of each doing the same sort of sound?

And of course, this isn't really what I'm after in this thread... Wink

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Time flies like a banana.
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Blue Hell
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PostPosted: Fri Jun 08, 2018 10:24 am    Post subject: Reply with quote  Mark this post and the followings unread

The difference sonically would be that for PM you'd have a larger modulation depth with a higher frequency of the modulator .. as compared to FM .. as the faster signal has a higher rate of change.

But yeah its hardly about filters anymore Laughing

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