How do I fix the output of my analog sound equalizer?

[moriavia]

I'm new to electronics and I'm trying to build an analog sound equalizer with an TL071 as an amplifier. I have three different circuits for three different ranges (low frequencies, high frequencies and medium frequencies). Each circuit for each range seems to be working fine, but the output (pin 6) doesn't change as expected. It should filter the signal according to the positions of each potentiometer.

The ampOp is in an adder configuration.

I tried messing with the resistors values, but to no effect. I know I can adjust each gain individually, but it didn't work.

Here's the full circuit (The last resistor is for measuring the output)

Circuit made with Multisim

For more information: the input is the audio output of a phone (2V) and the output should also be around that value, because I want to use it in a regular sound box

How can I fix it?

[Benta]

The opamp output is connected to ground through a 100 megaohms resistor. I don't see how that should work. I don't even see where the output is, or where it's supposed to be.

[moriavia]

The output is between pin 6 and gnd. I put the resistor to act as the load. I'm measuring the output on pin 6

[pqass]

The V2 symbol should be vertically flipped.
As is, pin 4 and 7 are connected to +12V so the chip is effectively unpowered.

[moriavia]

I think it's not visible in the image, but pin for is connected to -12V. The symbol is incorrect, but the output is -12V (I've measured it)

[pqass]

I think it's not visible in the image, but pin for is connected to -12V. The symbol is incorrect, but the output is -12V (I've measured it)

Then there should be +24 between pin 7 (red lead) and pin 4 (black lead of MM). Right?

[moriavia]

Precisely. There is. My output is not zero, but it's not being filtered correctly. It's not "equalizing"

[pqass]

You should read this.

[moriavia]

Thank you! I will read it, but it looks like all the filters featured in this are active. My problem is with the AmpOp as the adder. Thanks regardless

[Benta]

Precisely. There is. My output is not zero, but it's not being filtered correctly. It's not "equalizing"

I'm not surprised. To begin with, you're using first-order filters that do not really filter a lot.
But the major problem is that you think you can just add the amplitudes of the filters. You can't. Phase relation needs to be included, and that will give you a different picture.
If you're using Multisim, please show the simulation plots.

[moriavia]

What would be more helpful? AC sweeps with one pot at 100% and 2 at 0%?

[pqass]

I don't think the summing amp is your problem. You need to buffer the filter outputs before the pots.
You could adapt Figure 18 from here.

[Benta]

What would be more helpful? AC sweeps with one pot at 100% and 2 at 0%?

Yep, try showing that.

From my pocket calculator I see a LP at around 580 Hz if R13 and R14 are at zero (with 75% amplitude). And a 4.6 kHz HP when R14 and R15 are at zero.
Set R8 to 10%.
Try plotting those two situations.

[wasedadoc]

What would be more helpful? AC sweeps with one pot at 100% and 2 at 0%?

Yep, try showing that.

From my pocket calculator I see a LP at around 580 Hz if R13 and R14 are at zero (with 75% amplitude). And a 4.6 kHz HP when R14 and R15 are at zero.
Set R8 to 10%.
Try plotting those two situations.

Adjusting R8 has no effect on frequency responses.  Only on gain.

[pqass]

If you buffer your filters, it seems to work.  See attached screenshots.
Each screenshot shows one pot (LPF, MID, HPF) in the max. position, the rest on min.
The sweep is from 100Hz to 15kHz and back; upper showing the source, lower showing the output (100M load).
The ALL.png shows all pots to the max which produces a bit of a lumpy output; not flat.
Actually, given the Vrms differences in the outputs shown, you're probably going to have to trim/scale each stage for a normalized output.

Play with it here; see right margin for LPF,HPF,MID pot sliders, max is to the left, min to the right.