Hi guys,
I'm trying to build an audio amplifier with tone control for one of my circuit design courses. I'm supposed to use either the lm833 or the ne5534 opamp to provide a gain of 10 and supplying maximum power to a resistive speaker load, upto 20 khz. The circuit should also be able to boost the treble and bass and provide attenuation up to 10dB before being fed to a speaker.
I have no idea about how to go about building this circuit. I got a hold of the lm833 datasheet, from here:
http://cache.national.com/ds/LM/LM833.pdf
and it has a circuit for tone control. But I'm not sure if it will do everything that I've been asked to do, or how to modify it to suit my requirements.
I'll be very grateful if anyone could provide any tips or hints on how to go about this, because I have to complete this project as soon as possible.
Thanks in advance.
Dev
I'm trying to build an audio amplifier with tone control for one of my circuit design courses. I'm supposed to use either the lm833 or the ne5534 opamp to provide a gain of 10 and supplying maximum power to a resistive speaker load, upto 20 khz. The circuit should also be able to boost the treble and bass and provide attenuation up to 10dB before being fed to a speaker.
I have no idea about how to go about building this circuit. I got a hold of the lm833 datasheet, from here:
http://cache.national.com/ds/LM/LM833.pdf
and it has a circuit for tone control. But I'm not sure if it will do everything that I've been asked to do, or how to modify it to suit my requirements.
I'll be very grateful if anyone could provide any tips or hints on how to go about this, because I have to complete this project as soon as possible.
Thanks in advance.
Dev
The tone control schematic in the datasheet seems to be just what you're looking for; you'll just have to tailor the component values to suit whichever frequencies you'll want to boost/cut.
And regarding the attenuation... Wouldn't that be simplest to do with a pot, or a stepped attenuator? And i do hope that resistive speaker has a considerable resistance, because this poor little chip can't dissipate a lot of heat without burning up in the process
And regarding the attenuation... Wouldn't that be simplest to do with a pot, or a stepped attenuator? And i do hope that resistive speaker has a considerable resistance, because this poor little chip can't dissipate a lot of heat without burning up in the process
This chip will serve as a tone control only. It will boost and cut both bass and treble. You can use the values on the schematic. One circuit per channel.
But, this will have to feed a power amp that will deliver 20 watts at 20khz to meet your project requirements as you expressed them. Also, depending on the input signal level, you may need a preamp stage.
You might seek advice in the chip amp forum since you sound like you are in a hurry.
Don't jump on me guys! He didn't specify the amp had to be a discrete.
But, this will have to feed a power amp that will deliver 20 watts at 20khz to meet your project requirements as you expressed them. Also, depending on the input signal level, you may need a preamp stage.
You might seek advice in the chip amp forum since you sound like you are in a hurry.
Don't jump on me guys! He didn't specify the amp had to be a discrete.
Leolabs,
where do you live in Bukit Mertajam? it must be hard for you to get good quality parts over there...
I am an ex-Penangnite...now I live in Melb., there you go.
where do you live in Bukit Mertajam? it must be hard for you to get good quality parts over there...
I am an ex-Penangnite...now I live in Melb., there you go.
I am not so familar with B.M.
Buy via post, you can pay now via Paypal, much cheaper transaction cost. Postal charges are the killer.
with US dollar dropping you must find parts getting more expensive? good for exporters and not for importers.
any chance of ringgit revaluing?
Buy via post, you can pay now via Paypal, much cheaper transaction cost. Postal charges are the killer.
with US dollar dropping you must find parts getting more expensive? good for exporters and not for importers.
any chance of ringgit revaluing?
Don't mind about the price as long as it's worth the price.Do u have any MSN contact???Sounds like we are hacking Thisisme's topic here.
I am not working, are you?
don't let your boss catch you on the net?
sorry I don't have MSN. you can email me the address can be found using my profile if you like.
signing off...
don't let your boss catch you on the net?
sorry I don't have MSN. you can email me the address can be found using my profile if you like.
signing off...
re
Thanks a lot for the help guys! Are there any any power amps that I could use besides the LM1875? How do I decide which is the best power amp suited for the job?
Also, about the attenuation, would that go in the tone control stage or the power amp stage?
Thanks again!
Dev
Thanks a lot for the help guys! Are there any any power amps that I could use besides the LM1875? How do I decide which is the best power amp suited for the job?
Also, about the attenuation, would that go in the tone control stage or the power amp stage?
Thanks again!
Dev
You have a LONG way to go. You are going to have to build a power supply for the power amp and a separate regulated power supply for the tone control IC and preamp if needed. A start up delay may also be required for the power amp section.
Attenuation is normally at the input of an audio circuit. The fact that you ask this indicates you are new to audio circuits. We all have to start some where. The is an abundance of information on the net.
To build and UNDERSTAND a project like this you will spend much more time researching than actually building.
Attenuation is normally at the input of an audio circuit. The fact that you ask this indicates you are new to audio circuits. We all have to start some where. The is an abundance of information on the net.
To build and UNDERSTAND a project like this you will spend much more time researching than actually building.
I would put the attenuator BEFORE the active tone control stage.
If you put it after, the opamp will almost certainly overload on most source voltages and particularly when boost is applied.
Who says he needs a power amp for this design exercise?
150mW into 1000r load needs +-21Vdc and sends <25mApk, which is inside the range of a 5534.
If 300ohm headphones were the load, then just reduce the supply voltage to about +-12Vdc and you'll still get peak output well in excess of 100db.
Is this a trick question that has been set?
If you put it after, the opamp will almost certainly overload on most source voltages and particularly when boost is applied.
Who says he needs a power amp for this design exercise?
150mW into 1000r load needs +-21Vdc and sends <25mApk, which is inside the range of a 5534.
If 300ohm headphones were the load, then just reduce the supply voltage to about +-12Vdc and you'll still get peak output well in excess of 100db.
Is this a trick question that has been set?
My bad! I thought I read he needed a 20 watt output.
You can get by with two batteries as a supply for this chip.
Sorry for the confusion.
You can get by with two batteries as a supply for this chip.
Sorry for the confusion.
re
Thanks again for the help guys, especially AndrewT. I thought that this was going to be a pretty complicated project from what davidlzimmer said! 😛
I've been told that I could go with a three stage design: first stage would be an LM833 for the volume control, second would be another LM833 for tone control, and third would be the NE5534 for amplification and supplying the output to the speaker. What do you think of that configuration?
Thanks in advance.
Dev
Thanks again for the help guys, especially AndrewT. I thought that this was going to be a pretty complicated project from what davidlzimmer said! 😛
I've been told that I could go with a three stage design: first stage would be an LM833 for the volume control, second would be another LM833 for tone control, and third would be the NE5534 for amplification and supplying the output to the speaker. What do you think of that configuration?
Thanks in advance.
Dev
Whoever gave you that assignment, is on drugs.
Assume your 10x gain on a 1v signal...... i.e. 10V output.
The majority of speakers are 4 or 8 ohms... 10v over 8 ohm = 1.25A and this doubles for 4 ohm.
The chip can not even do a 10th of that current... If he wants you to do a headphone amp, things change a little, but a 10x gain would be excessive again... so either way the consept behind the project seems flawed... I.e. an amp that drivesa speaker to sound like a mosquito, or a headphone amp with insane gain and probably noise floor.
Please correct me, if I had too much coffee.
Assume your 10x gain on a 1v signal...... i.e. 10V output.
The majority of speakers are 4 or 8 ohms... 10v over 8 ohm = 1.25A and this doubles for 4 ohm.
The chip can not even do a 10th of that current... If he wants you to do a headphone amp, things change a little, but a 10x gain would be excessive again... so either way the consept behind the project seems flawed... I.e. an amp that drivesa speaker to sound like a mosquito, or a headphone amp with insane gain and probably noise floor.
Please correct me, if I had too much coffee.
They don't specify that he needs a large wattage output - just to drive a speaker. You could of course do that with an opamp followed by a Class B current stage using two transistors and some diodes.
Ok, I tried to build the circuit in Electronics Workbench (now called MultiSim 10), but I am getting some weird outputs. The tone control seems to be working alright, but I am getting upto 1kVp-p at the output of the NE5534. I'd be really grateful if anyone here could help me out...I'm sure I've connected something wrong, but I'm not sure what. Also, I'm not quite sure what to do with pins 5 and 1 of the NE5534. According to the data sheet, pin 5 is for comparison and pin 1 is for balance. Do I connect them both to ground? What about pin 8? That doesn't even show up in the Multisim model.
Here's the circuit diagram:
Here's the output at the NE5534 (check channel B on the scope):
And here's the output at the 2nd LM833 (channel A on the scope):
These are the worst case conditions i.e. When the 100K pot is set to 50% and the 500K pot is set to 0%, I get max voltage output at the NE5534.
I have to present this circuit this Friday, so any help would be greatly appreciated! 🙂
Here's the circuit diagram:
An externally hosted image should be here but it was not working when we last tested it.
Here's the output at the NE5534 (check channel B on the scope):
An externally hosted image should be here but it was not working when we last tested it.
And here's the output at the 2nd LM833 (channel A on the scope):
An externally hosted image should be here but it was not working when we last tested it.
These are the worst case conditions i.e. When the 100K pot is set to 50% and the 500K pot is set to 0%, I get max voltage output at the NE5534.
I have to present this circuit this Friday, so any help would be greatly appreciated! 🙂
There are several issues here. At first sight, there is nothing wrong with the circuit. But look at R12, 500k, and those two 3.6k resistors. With the pot all the way to the right, the gain for hi freqs is over a hundred. With the other gain in the circuit, you easily have 1kV at the output. So, first step, make the pot-and-resistor values in the lower tone control arm the same as for the lows - 11k and 100k. That limits the max hi freq gain to about 20dB as shown in the app note. Yes, I think that app note is in error.
Next, lower your input level to 100mV, to create some tone control headroom.
Still, you have a LOT of tone control range, up to 20dB. That's huge. On both the low and hi freq arm, change the pot to 50k, that should give you about +/-12dB range. Now, your turnover points may be off, so you may need to adjust the caps in the tone circuit.
The question remains why the sim happily gives 1kV from 15V supplies. I would guess that you use standard 'ideal' opamp elements, renamed to 833 etc? Nothing wrong with that, but some of those opamp models can really act weird.
See how it works now.
Jan Didden
Next, lower your input level to 100mV, to create some tone control headroom.
Still, you have a LOT of tone control range, up to 20dB. That's huge. On both the low and hi freq arm, change the pot to 50k, that should give you about +/-12dB range. Now, your turnover points may be off, so you may need to adjust the caps in the tone circuit.
The question remains why the sim happily gives 1kV from 15V supplies. I would guess that you use standard 'ideal' opamp elements, renamed to 833 etc? Nothing wrong with that, but some of those opamp models can really act weird.
See how it works now.
Jan Didden
Ok, I talked to my professor today, and cleared up a few things. It seems that I am supposed to use a power amp (chip or BJTs) to drive a speaker load. Prof said that the speaker load might be about 8-10 ohms, not anywhere close to the 600 ohms that I thought.
The whole confusion arose because our lab supervisor told us that we were only supposed to use the lm833/ne5534, but our Professor cleared that up. So it's back to the drawing board for us now. I asked him if we could use the LM386 to drive the speaker load, and he said that he would talk to our lab supervisor about it and clear up the matter tomorrow.
I'm really sorry for the confusion. Would anyone mind recommending some power amp (chip or BJT) to drive a 8 ohm speaker load? I guess I'll just have to replace the ne5534 with the power amp then?
Thanks again for your help!
The whole confusion arose because our lab supervisor told us that we were only supposed to use the lm833/ne5534, but our Professor cleared that up. So it's back to the drawing board for us now. I asked him if we could use the LM386 to drive the speaker load, and he said that he would talk to our lab supervisor about it and clear up the matter tomorrow.
I'm really sorry for the confusion. Would anyone mind recommending some power amp (chip or BJT) to drive a 8 ohm speaker load? I guess I'll just have to replace the ne5534 with the power amp then?
Thanks again for your help!
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