q ing a circuit. low and high pass filter.

[Ansil]

so anyway when imake a filter the freq that it doesn't let by go to gournd.

do i have to send them to ground or can i send them like to an opamps feedback loop.?

so say i set up a lowpass and a high pass filter.  and depending which way i turn it will it inject the opamps negative feedback loop..basically i am jsut remobiing the ground and adding it to the negative opamp side.
any ideaaaas

[Mike Burgundy]

you can do a lot of shaping in the feedback loop: a series cap in the loop will let through more highs, so the entire opamp setup will be lowpass. You can hook up a cap to ground from the feedback loop to remove some highs from the loop, etc.
But yes, both a cap to ground and a cap in the negative feedback loop are both low-pass systems.

[Ansil]

you can do a lot of shaping in the feedback loop: a series cap in the loop will let through more highs, so the entire opamp setup will be lowpass. You can hook up a cap to ground from the feedback loop to remove some highs from the loop, etc.
But yes, both a cap to ground and a cap in the negative feedback loop are both low-pass systems.

yeppers i know that one. but i am working with a strange opamp taht doesnt' really work normally..  anyway..  heres what i am lookin at

http://www.geocities.com/austenfantanio//whatiamasking.htm

[Jason Stout]

I think I know what Ansil wants...He wants to send the filtered bands to be manipulated elsewhere...not sent to ground or  thrown in the trash.
Ansil I am sure it can be done, look up opamp virtual ground....
Jason

[Ansil]

ahh..   thank you grasshopper..

[Ansil]

see i am gonna split certain freq's and have the negative inptu of the opamp take off highs.. but have the positive side feedback a certain amount.. via an external sustain switch.   which will have a preset trimmer to determine how long the note will feedback before the ldr will drop its resistance thus making the filter ground otu.  essentially makin it due what i am trying to trick into doing now.

[Jason Stout]

Ansil, I'm not quite sure of what you are trying, but it might be easier with 3 opamps, one to filter, one to amplify the filtered band and one to sum. The positive feedback in your diagram looks hard to control to me.
Jason

[Ansil]

it will have a variable knob to set the amount of gain.  and a momentary foot switch that has some sort of led ldr reader that will essentially move the positive feedback away when it reaches a certain level..

[Mike Burgundy]

ok, wow. Cool idea.
The floating ground thing is a good tip on this, otherwise I say just wire the bugger up and see...
Let us know, this might be a very cool one. There's something in the back of my head on old EQ's that have something to do with this, but I can't put my finger on it. anyone?

[Ansil]

i was thinking if we make a basic distortion circuit. and use the high roll off of the standard opamp feedback loop.  and if the freq response is right on the money i was talkin about..  it will feedback 720hz and up.. and of course automaticaly the extended highs get rolled off.  but if i set the feedback level say 10-15% higher than the normal distortion circuit. when i hit the feedback pedl(a momentary switch i get a feedback circuit that is really feedback not synthisized like that boss pedal) i may have to use three opamps.. one for drive one for feedback and one to either combine or notch out the overtone...  anyway.  it is a work in process..

[Ansil]

new thread circuit posted up top

http://www.geocities.com/austenfantanio//feedbacker.htm