In the link from post #25 there is a table, which provides information on how to increase the gain. It is a question of choosing the relation for R3L/R4L or R7L/R8L.
In mjf's schematic instead of a fixed resistor a 10 k trimmer is used to do the same thing. Gain is (R4L + R3L) / R4L or (R8L + R7L) / R7L or in mjf's schematic (2,2 + 2,2 + present trimmer value) / 2,2
If those preamplifier schematics don't help, the culprit is probably your subwoofer driver. It is either in the wrong enclosure or not adequate to serve as subwoofer. Not every driver is good for that, even if it is a good driver for other tasks.
Did you already install the low-pass filter for it? If not, then it will add more SPL to the midrange than to the bass and never sound right.
In mjf's schematic instead of a fixed resistor a 10 k trimmer is used to do the same thing. Gain is (R4L + R3L) / R4L or (R8L + R7L) / R7L or in mjf's schematic (2,2 + 2,2 + present trimmer value) / 2,2
If those preamplifier schematics don't help, the culprit is probably your subwoofer driver. It is either in the wrong enclosure or not adequate to serve as subwoofer. Not every driver is good for that, even if it is a good driver for other tasks.
Did you already install the low-pass filter for it? If not, then it will add more SPL to the midrange than to the bass and never sound right.
Thank you MJF
Your opamp with variable gain Schematic is sounding for me. It has solved my weak signal problem.
I altered with some components bcoz...
1) R 42K replaced with 47K ( Due to not availability at SHOP )
2) 4.7 uf 50v replaced with 150 uf 25v ( 150 uf improves BASS )
3) 10K Pot replaced with 100K ( Due to not availability at SHOP )
After all alteration opamp is sounding good independently.
Example..
Option 1 : DVD PLAYER ====> Opamp =====> Speaker ( Sounding good without any problems)
Option 2 : DVD PLAYER ====> Opamp =====> TDA1554q ====> Speaker ( Moving speaker driver Up/Down with OR without Sound. TDA1554q Input Caps is 10 uf 25v. WEAK SIGNAL IMPROVED.)
Option 3 : DVD PLAYER ====> TDA1554q ====> Speaker ( Sounding good accept weak sound, no any problem. )
Please do required correction for me.
Thank you & Regards.
Your opamp with variable gain Schematic is sounding for me. It has solved my weak signal problem.
I altered with some components bcoz...
1) R 42K replaced with 47K ( Due to not availability at SHOP )
2) 4.7 uf 50v replaced with 150 uf 25v ( 150 uf improves BASS )
3) 10K Pot replaced with 100K ( Due to not availability at SHOP )
After all alteration opamp is sounding good independently.
Example..
Option 1 : DVD PLAYER ====> Opamp =====> Speaker ( Sounding good without any problems)
Option 2 : DVD PLAYER ====> Opamp =====> TDA1554q ====> Speaker ( Moving speaker driver Up/Down with OR without Sound. TDA1554q Input Caps is 10 uf 25v. WEAK SIGNAL IMPROVED.)
Option 3 : DVD PLAYER ====> TDA1554q ====> Speaker ( Sounding good accept weak sound, no any problem. )
Please do required correction for me.
Thank you & Regards.
Hello
Something wrong. Pl find attached picture & do required corrections.
I have tried opamp with three options. Source sound supply is DVD Player. Power Amplifier is TDA1554q. I wish to add Opamp between DVD Player & TDA1554q as Subwoofer signal inhancer or active crossover with good gain.
My problem is TDA1554q is sounding good but weak in case of subwoofer. becoz DVD Player sub-signal is weak to amplify by TDA1554q. I am going to improve sub-signal by your OPAMP.
Thank you & Regards
Something wrong. Pl find attached picture & do required corrections.
I have tried opamp with three options. Source sound supply is DVD Player. Power Amplifier is TDA1554q. I wish to add Opamp between DVD Player & TDA1554q as Subwoofer signal inhancer or active crossover with good gain.
My problem is TDA1554q is sounding good but weak in case of subwoofer. becoz DVD Player sub-signal is weak to amplify by TDA1554q. I am going to improve sub-signal by your OPAMP.
Thank you & Regards
Attachments
hello.
is the woofer moving slowly in and out?........ there could be a problem with your mains (voltage slowly drifting or so...........).
disconnect your dvdplayer and look if the woofer is moving on.
perhaps try to test your system with a cdplayer or something else.....................
some other suggestions:
a 150uf cap at the output of the opamp is a big thing - you can use it to enhance the psvrr of the tda 1554q (look at the datasheet): connect the 150uf with the +pole to pin 4 and with the -pole to ground.this can clean your powersupply a little bit.
for outputcap you can use a 10uf electrolytic.
greetings..............
is the woofer moving slowly in and out?........ there could be a problem with your mains (voltage slowly drifting or so...........).
disconnect your dvdplayer and look if the woofer is moving on.
perhaps try to test your system with a cdplayer or something else.....................
some other suggestions:
a 150uf cap at the output of the opamp is a big thing - you can use it to enhance the psvrr of the tda 1554q (look at the datasheet): connect the 150uf with the +pole to pin 4 and with the -pole to ground.this can clean your powersupply a little bit.
for outputcap you can use a 10uf electrolytic.
greetings..............
What he means to say is that there is a low-frequency oscillation which is causing the woofer cone to move even with no input signal.
Pra(kash/deep, whatever), layout of the components is critical if you are not using a PCB. Decoupling needs to be kept close to the chip. Signal paths need to be very short. Filtering needs to be proper. Your problem could be stray pickup from airborne interference, or the input signal coupling through the air to the power supply (which is what I suspect). You may have not employed any bandwidth limiting either.
What I would do is:
Fit a IC socket on to a PCB.
Wire in all components, ensuring that the signal travel length is not more than the distance of the component.
Ensure a regulated supply for the opamp. 7812/7912 should be enough.
You will need a split supply, which can have both + and - voltages.
Use a 1nF cap between the input pins of the opamp, to limit the bandwidth for the subwoofer part.
Don't cross the power lines with the signal lines, ever. Keep at least a few centimeters distance.
Finally, separate your power and signal grounds, and join them at only one point.
Your circuit is also pretty wonky.
Put the pot in the signal path, not feedback path.
The bias needs to be coupled to the + input through a small resistor, and also needs a small capacitor to provide a bit of reserve.
IMO 100K is too large, use a divider of 22K resistors with 22uF cap, and use a 47K resistor to connect it to the +pin.
The feedback resistors are too large all around. A combination of 22K and 4.7K will yield 18dB of gain, enough for you.
22uF will work fine with that set of values, as you're using.
Finally, reduce the output cap value. 150uF is too large and will have much poorer ESR than smaller types.
Pra(kash/deep, whatever), layout of the components is critical if you are not using a PCB. Decoupling needs to be kept close to the chip. Signal paths need to be very short. Filtering needs to be proper. Your problem could be stray pickup from airborne interference, or the input signal coupling through the air to the power supply (which is what I suspect). You may have not employed any bandwidth limiting either.
What I would do is:
Fit a IC socket on to a PCB.
Wire in all components, ensuring that the signal travel length is not more than the distance of the component.
Ensure a regulated supply for the opamp. 7812/7912 should be enough.
You will need a split supply, which can have both + and - voltages.
Use a 1nF cap between the input pins of the opamp, to limit the bandwidth for the subwoofer part.
Don't cross the power lines with the signal lines, ever. Keep at least a few centimeters distance.
Finally, separate your power and signal grounds, and join them at only one point.
Your circuit is also pretty wonky.
Put the pot in the signal path, not feedback path.
The bias needs to be coupled to the + input through a small resistor, and also needs a small capacitor to provide a bit of reserve.
IMO 100K is too large, use a divider of 22K resistors with 22uF cap, and use a 47K resistor to connect it to the +pin.
The feedback resistors are too large all around. A combination of 22K and 4.7K will yield 18dB of gain, enough for you.
22uF will work fine with that set of values, as you're using.
Finally, reduce the output cap value. 150uF is too large and will have much poorer ESR than smaller types.
hello.
schematic in post 40 is a standardapplication,often used in preamps,mixers and so on.......
i have built some of them and they always worked without problems.
i will have a look at this problem tonight or tomorrow.
in the meantime you can try this: change the 22uf elcap (in the feedback loop) to a 1uf cap (because you changed the rc- arrangement to a much bigger value).perhaps this is the problem.........
greetings...........
schematic in post 40 is a standardapplication,often used in preamps,mixers and so on.......
i have built some of them and they always worked without problems.
i will have a look at this problem tonight or tomorrow.
in the meantime you can try this: change the 22uf elcap (in the feedback loop) to a 1uf cap (because you changed the rc- arrangement to a much bigger value).perhaps this is the problem.........
greetings...........
Thank you sangram
<layout of the components is critical if you are not using a PCB.>
[I am not using a special PCB. Using general ready-made PCB]
<You may have not employed any bandwidth limiting either.>
[what is that?]
<Ensure a regulated supply for the opamp. 7812/7912 should>
[I think I have used regulated supply bcoz I have used IC:7812]
<You will need a split supply, which can have both + and - voltages.>
[No I don't have + and -. I have only + and ground ]
<Use a 1nF cap between the input pins of the opamp, to limit the bandwidth for the subwoofer part.>
[Exactly where should I use it]
Your further remark is BOUNCED to me. Forgive me I am not an electronics man.
I understand schematic language. You are requested to make required correction to my altered schematic or make new one which is suitable for me.
Thank you, Regards.
<layout of the components is critical if you are not using a PCB.>
[I am not using a special PCB. Using general ready-made PCB]
<You may have not employed any bandwidth limiting either.>
[what is that?]
<Ensure a regulated supply for the opamp. 7812/7912 should>
[I think I have used regulated supply bcoz I have used IC:7812]
<You will need a split supply, which can have both + and - voltages.>
[No I don't have + and -. I have only + and ground ]
<Use a 1nF cap between the input pins of the opamp, to limit the bandwidth for the subwoofer part.>
[Exactly where should I use it]
Your further remark is BOUNCED to me. Forgive me I am not an electronics man.
I understand schematic language. You are requested to make required correction to my altered schematic or make new one which is suitable for me.
Thank you, Regards.
I'm sorry if this sounds bad, but you'll need to read a little bit if you're going to attempt something like this. Nuuk's Decibel Dungeon, Rod Eliot's ESP site are good places to start. No pain, no gain. The problem is not restricted to a schematic. The actual construction may be an issue, so no amount of scrawling in Paint will help. Just a lot of reading and building, then trying again. You'll have to learn basic grammer and spelling if you want to talk, so in the same way you need some basics.
Once again, here goes:
Fit a IC socket on to a PCB. What did you not understand of this?
Wire in all components, ensuring that the signal travel length is not more than the distance of the component. The leads should be trimmed close to the package. As short as possible. Plan your layout accordingly.
Use a 1nF cap between the input pins of the opamp, to limit the bandwidth for the subwoofer part. that would be pin 2 and pin 3. Read about an opamp and how it works.
Don't cross the power lines with the signal lines, ever. Keep at least a few centimeters distance. What did you not understand? The wires and components need to be at a distance from each other, crossing only at right angles.
Finally, separate your power and signal grounds, and join them at only one point. The signal ground is where the signal input and ground come to. The output ground is where you take the output from. The power ground is where the voltage divider is referenced to ground, and the voltage regulator is grounded to.
Put the pot in the signal path, not feedback path. Pot should be before the input, or after the output of the opamp - remove it from there. You know, connect like a normal volume control - one pin to ground, one to input, one to output, like you normally do.
The bias needs to be coupled to the + input through a small resistor, and also needs a small capacitor to provide a bit of reserve. IMO 100K is too large, use a divider of 22K resistors with 22uF cap, and use a 47K resistor to connect it to the +pin.
The above refers to the two 100K resistors forming the voltage divider to set the supply half-bias since you have a single supply. First, the divider resistors need to be a little lower. A capacitor from the midpoint will act as a small supply reserve. Then a resistor should be used to connect pin 3 from this half point. As of now pin 3 is directly connected to the half bias point. Not a good idea.
The feedback resistors are too large all around. A combination of 22K and 4.7K will yield 18dB of gain, enough for you. 22uF will work fine with that set of values, as you're using. The feedback resistors come from Pin 1 to 2 and with the RC network to ground. There should be a 22K from pin 1 to 2, and a 4.7K and 22uF from pin 2 to ground.
Finally, reduce the output cap value. 150uF is too large and will have much poorer ESR than smaller types. This is clear, hopefully. A 10uF cap is adequate here. Please do not connect the NE5532 directly to the speaker (as you indicate in your drawing), any damage will be permanent and will ultimately spoil your sound quality - it may already have, so you may anyway advised to get a new IC or use the other half.
Once again, here goes:
Fit a IC socket on to a PCB. What did you not understand of this?
Wire in all components, ensuring that the signal travel length is not more than the distance of the component. The leads should be trimmed close to the package. As short as possible. Plan your layout accordingly.
Use a 1nF cap between the input pins of the opamp, to limit the bandwidth for the subwoofer part. that would be pin 2 and pin 3. Read about an opamp and how it works.
Don't cross the power lines with the signal lines, ever. Keep at least a few centimeters distance. What did you not understand? The wires and components need to be at a distance from each other, crossing only at right angles.
Finally, separate your power and signal grounds, and join them at only one point. The signal ground is where the signal input and ground come to. The output ground is where you take the output from. The power ground is where the voltage divider is referenced to ground, and the voltage regulator is grounded to.
Put the pot in the signal path, not feedback path. Pot should be before the input, or after the output of the opamp - remove it from there. You know, connect like a normal volume control - one pin to ground, one to input, one to output, like you normally do.
The bias needs to be coupled to the + input through a small resistor, and also needs a small capacitor to provide a bit of reserve. IMO 100K is too large, use a divider of 22K resistors with 22uF cap, and use a 47K resistor to connect it to the +pin.
The above refers to the two 100K resistors forming the voltage divider to set the supply half-bias since you have a single supply. First, the divider resistors need to be a little lower. A capacitor from the midpoint will act as a small supply reserve. Then a resistor should be used to connect pin 3 from this half point. As of now pin 3 is directly connected to the half bias point. Not a good idea.
The feedback resistors are too large all around. A combination of 22K and 4.7K will yield 18dB of gain, enough for you. 22uF will work fine with that set of values, as you're using. The feedback resistors come from Pin 1 to 2 and with the RC network to ground. There should be a 22K from pin 1 to 2, and a 4.7K and 22uF from pin 2 to ground.
Finally, reduce the output cap value. 150uF is too large and will have much poorer ESR than smaller types. This is clear, hopefully. A 10uF cap is adequate here. Please do not connect the NE5532 directly to the speaker (as you indicate in your drawing), any damage will be permanent and will ultimately spoil your sound quality - it may already have, so you may anyway advised to get a new IC or use the other half.
I would increase the cap after the 7812 to mitigate the hum problem.
However beyond this point I would need to look at a close-up of the layout to sort out any hum issues. The circuit looks much cleaner to me now.
Edit: Is that connection of the feedback 22uF cap to the midpoint a typo? Maybe that is what is causing the hum. There should be no connection there, it will lead to some DC at the output.
@PB: In such case I would use a large amount of gain, say x6 or x10 if possible so as to get the max possible swing, and use a pot at the output to only attenuate. Yes the noise is also worsened by this approach but it can serve as a base to determine the final gain required. The pot can be removed or kept as close to its maximum position as possible once the resistors are finally set for the right amount of gain. Anyway the partnering equipment will be sensitive to only the most brutish forms of noise. There's only the best practices I've learnt on this forum and IME that I can pass on.
However beyond this point I would need to look at a close-up of the layout to sort out any hum issues. The circuit looks much cleaner to me now.
Edit: Is that connection of the feedback 22uF cap to the midpoint a typo? Maybe that is what is causing the hum. There should be no connection there, it will lead to some DC at the output.
@PB: In such case I would use a large amount of gain, say x6 or x10 if possible so as to get the max possible swing, and use a pot at the output to only attenuate. Yes the noise is also worsened by this approach but it can serve as a base to determine the final gain required. The pot can be removed or kept as close to its maximum position as possible once the resistors are finally set for the right amount of gain. Anyway the partnering equipment will be sensitive to only the most brutish forms of noise. There's only the best practices I've learnt on this forum and IME that I can pass on.
From last 20 days approx, I was trying to develop subwoofer signal booster/preamplifier. Today I am very near to the complition.
Thank you sangram I will give you a STAR.
1) I could not remove HUMMM 100%, but now it is acceptable.
2) All channels sound pressure are equal now.
2) When system starts by power on, a strange (POOAK) sound comes from speakers & after 1-2 sec. system normalised.
3) With preamp my Sub-driver cone-movements are increased by 1/2" but still not sounding good as branded subwoofer. Branded means I don't expect as BOSS/YAMAHA. But should sound any good multi-media speakers (ALTEC-FX5051)
Still I do not added any CROSSOVER just boosting weak sub-signal with preamp right? As per my knowledge CROSSOVER able to change the shape of the sound. Dvd player already sending LOW frequency to opamp. Now enclosure type and size is the matter.
<Pasificblue advised : each driver has Thiele/Small parameters, with which you determine the right enclosure type and size?>
Sangram as you are from MUMBAI, you must know BOLTON woofers. I am using 8" (Bolton) and I have two amplifier so I can connect two 8" drivers. Please advise on right enclosure type and size for two 8" drivers as subwoofer unit.
Locally at my place speaker box maker says that PARTICLE BOX sounds good than MDF. Actually I have MDF box without any damping material & Size is 12"x12"x12" with 2" Port. I can scrap this. please advise the perfect size & style.
Thank you & Regards.
Thank you sangram I will give you a STAR.
1) I could not remove HUMMM 100%, but now it is acceptable.
2) All channels sound pressure are equal now.
2) When system starts by power on, a strange (POOAK) sound comes from speakers & after 1-2 sec. system normalised.
3) With preamp my Sub-driver cone-movements are increased by 1/2" but still not sounding good as branded subwoofer. Branded means I don't expect as BOSS/YAMAHA. But should sound any good multi-media speakers (ALTEC-FX5051)
Still I do not added any CROSSOVER just boosting weak sub-signal with preamp right? As per my knowledge CROSSOVER able to change the shape of the sound. Dvd player already sending LOW frequency to opamp. Now enclosure type and size is the matter.
<Pasificblue advised : each driver has Thiele/Small parameters, with which you determine the right enclosure type and size?>
Sangram as you are from MUMBAI, you must know BOLTON woofers. I am using 8" (Bolton) and I have two amplifier so I can connect two 8" drivers. Please advise on right enclosure type and size for two 8" drivers as subwoofer unit.
Locally at my place speaker box maker says that PARTICLE BOX sounds good than MDF. Actually I have MDF box without any damping material & Size is 12"x12"x12" with 2" Port. I can scrap this. please advise the perfect size & style.
Thank you & Regards.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.