has any one else tried a lm324 in Craig A.'s super tone control?

[foxfire]

i bread boarded this last night and got it to work, well sort of. i'll start with my part swaps,
1) swapped the rc4136 for a lm324
2) i'm using two 100k pots as i don't have any dual gang
3) swapped the 1n4607 for 1n4004
4) swapped the 2.7k res. for a 3k res.
other than the changes above it's as shown in his EPFM book.

the problem i'm having is when i about max the "cutoff frequency" pots i get a horrible squeal. i can't imagine that it's supposed to do that so i'm wondering if i need to adjust the circuit for the lm324?

[John Lyons]

I've built two so far. Search for craig anderton or state variable  and basicaudio or John Lyons as the user name.
Highly recommended build !!
I used the RC4136 and another equivilent (forget the number now...)
A dual pot is the only way to go as the circuit is balanced, or at least needs to have the freq control turned simutaneous to get the best sweep range and frequency.

You did use a dual power supply correct? (+ and - 9v as well as ground, "bipolar")
The Dual pot is best at 10K or 50K as far as I know.

As long as the chip is compatible it should be fine. I think I can spare a 4136 if you need it.

John

[foxfire]

i was hoping you would respond to this as i read many of your posts on this and it was your sound clip that made me want to try this circuit.
i am using bipolar supply for it. i know it has its merits but, what a pain. anyway a few weeks ago i built Tim E.'s gargletron with a jrc4558 but decided to try a tl072/82 just for kicks. well i got squealing at one end of the pot much like i am now. so i wasn't sure if there was something about the lm324 that i was missing? and thanks for the offer John. i've got 4 of the lm's maybe i'll take you up on it if i kill'em all. i may have a dual gang some where so i guess i should start looking.

oh i also breaded a colorsound inductorless wah. thats a fun little circuit too.

[Mark Hammer]

You can build that puppy with basically ANY 4 opamps.  State-variable filters aren't THAT fussy.  What you can't do is use the EPFM layout with a different chip since the 4136 pinout is pretty unique and does not correspond to the 324/TL074 pinout.

[foxfire]

yeah they definitely don't match. i went through and reworked it enough to get it on the breadboard. i did find a dual gang 50k pot in a working (well it was working) Akai gx-m10 cassette player. so i wired that in and i still get a nasty high pitched squeal with the pots maxed. i'm sure well i must have something wired up wrong.

[foxfire]

ok so i reworked the frequency pot as dividers as suggested in past posts. to get rid of the self oscillation i was getting at both ends of the pot. i had to swap R6 and R8 to 3.3K. i also used 220R from each lug1 to ground. i believe it to be working "correctly" now. if it seems funny that i had to make the changes or if there is a better way to do the same thing ... i'm still just guessing most of the time. thanks again for your help. here is a link t the schematic, http://i140.photobucket.com/albums/r23/foxfire3/CraigAsSTC.jpg.