anyone have hi/lo filter schematics with resonance control?

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The CalrEq, for example, just sets Q to low when shelving: http://gyraf.dk/gy_pd/calreq/calr_eq.gif

..which can be changed..

But agree - what are you trying to do? Some massive-passive-type of strangely-shaped low/high shelving?

Jakob E.
 
Like the others said, no idea which freq-ranges & slopes etc you need ?

For sound-sculpting, the Korg MS-20 filter comes to mind, HPF + LPF, each filter a freq & resonance control.
6 dB/oct high-pass, 12 dB/oct low-pass

several implementations, here's the later OTA-based version:

http://machines.hyperreal.org/manufacturers/Korg/MS-synths/schematics/KLM-307.GIF
 
to answer questions,

Here is a drawing example.

As for db slopes and so forth I have not gotten that far, still bradbording a few ideas.
 

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pucho812 said:
to answer questions,

Here is a drawing example.

As for db slopes and so forth I have not gotten that far, still bradbording a few ideas.
That looks like underdamped (Q) vs critically damped.

State variable filters allow you to control Q independently of other parameters. Like parametric EQ but those just use the BP output. You can grab HP or LP from a SVF as desired.

Not sure it would sound very useful. Underdamped filter stages are generally cascaded in series with over damped stages to deliver a maximally flat in band response with steep rolloff.

JR
 
I thought the Alembic preamps were also state variable filters, do you have a schematic, Moamps? Keen on seeing it.

Anyways, here's a 12dB VCF in a synth application: http://musicfromouterspace.com/analogsynth_new/STATEVARVCFFEB2006/STATEVARVCFFEB2006.html

 
One question has not been adressed, should there be voltage control/automation?
Probably, because else it would be close to an EQ with q/bandwith control.
But if so, most synth circuits using ota´s, transistors, fets are not very hifi (although good sounding)
Optocouplers having their own problems with matching and control linearity (/but low noise and distortion)
There are a lot of circuits with ssm2164/v2164, also that 2180, those are probably the best choice.
Mutable "Ripples" is very clean sounding 4 (or less) pole LP, the circuit can easily turned into HP too...
https://mutable-instruments.net/modules/ripples/open_source/
Also the classic Polyfusion 4pole HP/LP come to mind, classic sound
Moog also has HP, but without resonance/"emphasis"
 
Using underdamped filters (that rise before rolling off) is an old trick to get in band boost, and protective out of band cut.

The poster boy for this was the Bose 901 speaker active EQ...  The EQ incorporated an under damped HPF to create bass boost before rolling off very low bass. 

Bose_901_EQ_Adjustment.jpg


JR
 

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