Schematic for a Low pass - High pass - Band pass filter?

[Bernardduur]

Hello all!

I am searching for such a device...... low pass, high pass and band pass (and switchable would be great). Anyone knows a good schematic for this?

[George Giblet]

Thou shall search for a "state variable filter" and be happy.

[stm]

This should make you even happier...



Available in this site...
http://hem.passagen.se/robin2/effects.htm

[Bernardduur]

Thanks man! It is EXACTLY what I was searching for!

[Austin73]

Hey Bern, let me know how you get on with the schematic. I quite fancy it myself but not got the confidence to try it yet. Does it need dual power to work?

[Bernardduur]

Yes, it needs a dual voltage!

What is BTW the difference between the two? And (when it is put in a wah pedal) is the "wah" pot? The Q or the frequency?

[Ben N]

Get a copy of EPFM, and look for "Super Tone Control".  Paia may even still have boards or kits for it.  Also +/- voltage required.

Ben

[SeanCostello]

Single voltage supply state variable filter:

http://www.oldcrows.net/~jhaible/tonline_stuff/hj_wasp.html

[hank reynolds 3rd]

Bernard, the wah pot would be the frequency (the dual pots are like the LDR's in a mutron/mcmeat) ...

there's a schem that uses regulators that I use for dual supplies,can't think of the link off the top of my head..similar to the one here..
http://www.generalguitargadgets.com/index.php?option=content&task=view&id=191&Itemid=216

but I hacked the transformer off ,and used an AC wallwart

[Bernardduur]

Ah OK; thanks!

I will use a MAX4101 chip for the power

[slacker]

wouldn't it work with a single power supply if you made a 4.5volt vref and connected the last 3 opamps + inputs to that instead of ground?
The first opamp looks like it's biased by the output of the second one so that bit wouldn't need modifying.

[Bernardduur]

Another question: could I replace the frequency pot(s) with two LDR's....

Would love to put it in a sequenced pedal

[Paul Perry (Frostwave)]

Another question: could I replace the frequency pot(s) with two LDR's....

Absolutely, that was my thought immediately I saw it! In fact, you could take the LED drive from anychunk of circuit taht does it already, envelope follower, trem, whatever. Either two LDRs with the led sandwitched between them, or separate units wiht the two leds in series.

[Bernardduur]

Thanks. I am busy building it right now;