Switching Between Tone stacks and the like...

[Dylfish]

Hey Guys,

I've finally designed and bread boarded my first working booster from scratch thanks to the guys that frequent these forums but alas i have another question.

I am trying to wire up a switch that will either bypass a low pass filter to keep a "flat EQ" or roll off some of the highs at the flick of a switch.

One catch is since the LPF sucks the life out of the signal i wanted a gain recovery stage (TL071) that only kicks in when the LFP is engaged. my idea was for a spdt to either bypass the LPF (which joins back up) or allowing it to go on its merry way.

with out the TL071 stage I have tried what i thought would work, but it seems that when the LPF is disengaged the life is sucked out of the original signal anyway. (My assumption is its still going to ground?)



I tried putting a diode between the return to the circuit and the cap, but it seemed to make my sim go crazy so i take it that was an incorrect option?

Is there a way to isolate the 2 and have it so when the LPF is engaged then it goes into the TL071 (not on the image yet!) or when i wasn't it to bypass the recovery & LPF it keeps its full signal?

Cheers.

[armdnrdy]

Without reading every single word of your post, I think I get the idea of the problem you are encountering.

Try a DPDT to switch out the entire LPF.

[LucifersTrip]

I'm not 100% sure what you want, since some of those sentences are difficult to interpret...I'm not sure if you want the recovery
in the mix when there's no lpf.

If that's what you want, how about just using a dpdt and in one direction connect 1/4 and the other direction connect
1/2 and 3/4

[Dylfish]

Man that's a bonde moment.  Sorry for wasting your time

[LucifersTrip]

Man that's a bonde moment.  Sorry for wasting your time

it's never wasted time...you never know who might be helped

[Dylfish]

Without reading every single word of your post, I think I get the idea of the problem you are encountering.

Try a DPDT to switch out the entire LPF.

Hey mate, how did you get that stitch set up like that in multisim? it's easier to follow

[armdnrdy]

I just threw your drawing in MS Paint, cut and pasted the switch, labeled the new section.

It is a bit difficult to know what you have going on without seeing the whole drawing.

You might want to post the whole thing.

[Dylfish]

np thats cool, i fixed it. Cheers =)

[PRR]

[PRR]

> when the LPF is disengaged the life is sucked out of the original signal anyway.

Which says your source is not zero impedance, is likely a lot closer to 600 Ohms. (A TL072 has 300 Ohms inside; for small signals this is masked by NFB but large fast signals will be slew-limited.)

Anyway you want larger R because smaller C is less money.

Depending of course what you are driving.

Filters can't be seen in isolation. You need to show where it comes from and where it is going to.