[sdiy] simple filter things..

[Nils Pipenbrinck]

Hi List,

I'm back :) Changed my email and now I'm able to post again on the list..


And I also have a hand full of simple filter questions.. (not synth-related,
but you're kind of specialists when it comes to filters :)  I bought a
guitar headphone thing a couple of weeks ago (Johnson J-Station.. I can
recommend that thing to ever guitar player!). The headphone out of this
thing has a built in bass boost. And my headphones are of good quality.. So
when I practice guitar I massage my head with low frequency waves all the
time.

I thought about putting a simple tone control circuit behind the output of
that beast. So I toyed around with this circuit on a breadboard:
http://headwize.com/images/eq3.gif. Basically that thing works and does what
I want it to do, but it doesn't have enough "grip" for my application.

I guess this circuit has 6db.. I wonder what options I have to increase the
Q of this filter.. building two of them and chaining them would be a simple
solution. I would however need dual-pots for one channel and a quad pot for
stereo (I don't think these even exist...)

Isn't there a better way to raise the Q? I thought about using FET's as
variable resistors to replace the pots but I haven't ever calculated a
FET-circuit myself. Or I could dump the circuit at all and start with
something better (In fact I don't need the high and mid controls in 12db..
just the low control). Also controlling the HP-cutoff frequency (in usuable
ranges) would be cool..

    Nils Pipenbrinck


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