OK... so there is something odd going on.
The only thing that makes any sense is that the part connections are somehow incorrect... I know you say you have checked this though.
Can you show in detail exactly what point you have connected the ground return of the pot/resistor network too.
Maybe if you posted a detailed picture or two of it all showing the added components 🙂
The only thing that makes any sense is that the part connections are somehow incorrect... I know you say you have checked this though.
Can you show in detail exactly what point you have connected the ground return of the pot/resistor network too.
Maybe if you posted a detailed picture or two of it all showing the added components 🙂
Sorry for my delay
Here's the circuit I'm using right now:
Is it right?
Here's the circuit I'm using right now:
An externally hosted image should be here but it was not working when we last tested it.
Is it right?
When the J switch is open the operation is good (like my currently sub's filter) but when the switch is closed the loud sound come
Taking your circuit at face value, that is exactly as shown, what determines the input DC bias conditions ? Where does R2 go in other words ? The opamp needs a DC path to ground from pin 3. As it is it's floating and totally reliant on the source DC conditions.
If you keep it DC coupled at the input (as it is now), you need at least a resistor (say 10 to 47k) from the input to ground to define the DC conditions.
If you keep it DC coupled at the input (as it is now), you need at least a resistor (say 10 to 47k) from the input to ground to define the DC conditions.
I see what's happening. I'm ashamed that I didn't see it before.
The Opamps must run at unity gain in this circuit. Any additional gain will cause the stage to go into oscillation. There is positive feedback around each stage.
If you need additional gain, you'll need to add another Opamp on the input or the output.
The Opamps must run at unity gain in this circuit. Any additional gain will cause the stage to go into oscillation. There is positive feedback around each stage.
If you need additional gain, you'll need to add another Opamp on the input or the output.
Mooly what do you think about Frank Berry idea????
something like this before my original circuit will do the job?
An externally hosted image should be here but it was not working when we last tested it.
Your circuit needs a couple of additions.
Add a resistor from pin 3 to ground. 10k would be a good value.
The Opamp must have a ground reference on the input.
I would add another 10k resistor between the input and pin 3.
Add a resistor from pin 3 to ground. 10k would be a good value.
The Opamp must have a ground reference on the input.
I would add another 10k resistor between the input and pin 3.
Thank you so much Frank Berry
it works
is this circuit what you mean?
it works
is this circuit what you mean?
An externally hosted image should be here but it was not working when we last tested it.
Uhh Frank
could you help me with something else?
How much I can increase the gain ? this added op-amp cause a little humm on my subwoofer ( when any sound is not played) that without this stage and with my original op-amp (just the filter) I don't get any sound on my sub even if I put my ear on my sub
Can I remove this humm completely ?
could you help me with something else?
How much I can increase the gain ? this added op-amp cause a little humm on my subwoofer ( when any sound is not played) that without this stage and with my original op-amp (just the filter) I don't get any sound on my sub even if I put my ear on my sub
Can I remove this humm completely ?
This circuit shouldn't produce any additional hum. It will amplify any hum that is present on the input.
It may be a problem with the layout or a grounding issue. You may also need better filtering of the power supply outputs.
It may be a problem with the layout or a grounding issue. You may also need better filtering of the power supply outputs.
Did you build all of the circuits on a single circuitboard?
Can you post a photo of the circuits?
Can you post a photo of the circuits?
My currently sub's low pass filter has PCB
I built this new circuit on a breadboard
but I'm gonna build this PCB tonight.
I just want to make sure that every thing is perfect and doesn't need any changes so I can build the PCB
If you want I can post a picture of my currently low pass filter PCB????
I built this new circuit on a breadboard
but I'm gonna build this PCB tonight.
I just want to make sure that every thing is perfect and doesn't need any changes so I can build the PCB
If you want I can post a picture of my currently low pass filter PCB????
Hi Mooly
How are you?
Don't worry about it
it works just fine but I still have the questions in post 33
could you help me with it?
How are you?
Don't worry about it
it works just fine but I still have the questions in post 33
could you help me with it?
The gain can be increased a lot. More than you will ever need. Times 10, times 100.
You can reduce R4 down to 470 ohms or even lower (if you need).
Hum... there should be non. You need to short circuit the input to the circuit and work from there. That way there is no possibility of any external cause.
You can reduce R4 down to 470 ohms or even lower (if you need).
Hum... there should be non. You need to short circuit the input to the circuit and work from there. That way there is no possibility of any external cause.
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