Low Voltage Stereo Amplifier

[thedarkness3300]

I'm sorry, lecturer didnt really teach anything.. So i should connect the output of the TL072 to the gain of the LM386 (pin1 and pin8). and the (-) input and (+) input will be connected to the output of the LM386, is it correct? how about the Vcc(-) and Vcc(+)? where should i connect this?

 

[audioguru]

I'm sorry, lecturer didnt really teach anything.

There are many tutorials about a simple opamp amplifier circuit on the internet.

So i should connect the output of the TL072 to the gain of the LM386 (pin1 and pin8)?

Absolutely not!
The input of the LN386 is its pin3. A coupling capacitor must be used.

and the (-) input and (+) input will be connected to the output of the LM386, is it correct?

Absolutely not!
The output of the LM386 power amplifier feeds the speaker.
The output of the TL072 opamp feeds a coupling capacitor that feeds the pin3 input of the LM386.
The (+) input of the TL072 must be DC biased at about half the supply voltage and have a coupling capacitor from the volume control. The input to the volume control will need a coupling capacitor if your signal source has DC.
The (-) input of the TL072 opamp needs two negative feedback resistors and a capacitor to ground.

how about the Vcc(-) and Vcc(+)? where should i connect this?

The supply pins of the TL072 are shown on its datasheet (hint pin4 and pin8). Its sales sheet says its minimum supply is 7V.

 

[thedarkness3300]

Hey, should i connected like this? the vcc did i connected correctly? thanks alot!

 

[audioguru]

I cannot believe that you do not understand how to connect an extremely simple opamp circuit.

But now it is powered correctly if its supply is at least 7V.
But its two inputs and its output are connected to the wrong spots.
It also has no negative feedback.

I guess you didn't see my last reply.

 

[thedarkness3300]

oh i see. That means , the output of the TL072 will be connect to a capacitor and feeds to the pin3 input then only connect to the potentiometer.
The (-) input of the TL072 opamp will be connect to two resistors and a capacitor then straight connect to ground?
I'm still not so sure bout how to connect the (+) input.. how can i make it dc biased about half of the supply voltage?
Really thanks alot for helping brother! sorry i just saw ur post ..

 

[Hero999]

I thought you said you'd learned about op-amps.

I suggest you Google for an op-amp tutorial and ask your lecturer to teach you about op-amps.

An op-amp will not help you in this case because you said that the noise only occurs when the volume is turned up high meaning it's clipping which will happen when any amplifier. The LM386 is only a small amplifier IC, if you need more volume without the noise and distortion, you need to use a bigger and better amplfier IC or add a booster stage.

 

[thedarkness3300]

that's means op amp will not help me to make the sound clear? is there any other way? i have to use lm386 as the IC. . =(

 

[Hero999]

Simple, don't turn the volume up all the way.

Look at the datasheet for the LM386 and note the high distortion figures at higher power levels.

Don't worry about it, include a detailed explanation about why the output is distorted.

If you don't know, then Google for audio amplifier clipping for more information.

 

[thedarkness3300]

okay! Thanks Alot!!!

 

[thedarkness3300]

Is there any other way i can reduce the distortion? thanks for replying..

 

[Nigel Goodwin]

Is there any other way i can reduce the distortion? thanks for replying..

As you've been told, don't turn it up so loud - if you want it louder and undistorted, use a better amp and higher supply voltage.

 

[audioguru]

Is there any other way i can reduce the distortion?

You do not have a power supply voltage listed for the LM386 power amplifier and do not have its speaker impedance listed.
Its datasheet shows that if its power supply voltage is 6V and its speaker is 8 ohms then it has low distortion (0.2%) only when its output power is less than only 0.2 Watts which is almost nothing. If you turn up the volume only a little so the output power is 0.3 Watts then its distortion is over 7%.
If you use a TDA2822M amplifier instead then it has low distortion when its output power is 0.9 Watts which is a little louder than the 0.2 Watts from an LM386 amplifier.

If you use a real power amplifier IC like an LM3886, when it has a 70V supply and its speaker is 8 ohms then its distortion at 60 Watts is only 0.002%.