Resonant LPF

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

joaquins

Well-known member
Joined
Feb 25, 2012
Messages
1,927
Location
Argentina
I was thinking to do some resonant LPF like VOG from little labs... Sombody recomend me to do something like this, it sound huge in vocals and really deep on bass and kick. I couldn't find the schems but it seems to be a 4th order resonant LPF with variable frec and amplitude. It would be cool to add a resonace control too i guess, for do it more versatile.

The thing is that it's variable frec is from 20 to 300 Hz and it seems dificult to tune it well with a pot... I dont know how they do, maybe i open the one of my friend and see what's inside, but it will be in a while cos i'm far away from that studio.

I was thinking in someting like 2 LM13600 like MFOS http://www.musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&VPW=1261&VPH=513 (almost at the end)

Taking out the input mixer and voltage control inputs and adding a output mixer (dry/wet). Also will need some modifications for line level (lowering down 1M inputs, change TL082 for NE5532, etc) but I dont know how LM13600 works for pro audio, line level situations. At least I think the topology would work.

Waiting comments.

JS
 
Do you NEED voltage controlled frequency setting?

If not, build a simple state-variable filter

http://www.daycounter.com/Filters/StateVariableFilters/State-Variable-Filter-Design-Equations.phtml

..and adjust frequency with a dual pot.

As you can see, this is more or less equal to one section of the common parametric eq, e.g. the CalrEQ

Jakob E.
 
4 stages of LM13700 will not do good for noise and THD.
As Jakob says, do you need voltage control?
You could use a 4-gang pot for manual tuning, or if you want VC, you should consider using a quartet of THAT VCA's.
http://www.thatcorp.com/datashts/dn130.pdf
 
I dont need VC, but traking in a 4 gang pot could be a trouble to set the resonant frec too narrow and not to turn it into 2 diferent resonant frecs, or at least a not so narrow one.

I do need 4 pole filter so a simple state variable filter wouldn't work, a 4th order would work, of course... and still the pot tracking trouble and they are hard to find in Argentina...

Thanks for the answer... the project will be freezed untill  get a 4-gang pot, in the midtime I'll use a plugin I guess...

JS
 
Back
Top