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I have made an amplifier using TDA2002 but it's not working properly.

Pot. R1 is not included in mine as it doesn't make a lot of difference and produces noise when I try to adjust the volume.
How can this be solved?

Above a certain volume set in the music player, the 8 ohm, 3 inch diameter speaker gives out distorted sound.
How can I avoid this?

If the 3.5 mm jack isn't connected to an MP3 player or any audio device, there's a buzzing noise from the speaker.
How is this noise produced and how can it be removed?

A friend suggested that I add resistors in series to the input and the output. It din't work. So he suggested that I add a buffer circuit to the input.
Will that help?

EDIT: I'm using a 5V, 0.7A supply.

Here's the circuit diagram
enter image description here

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5 Answers 5

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Distortion

Distortion can be caused (in this amp, assuming everyting is connected like it should be) by one of four causes:

  1. Speakers gets overloaded - small speakers cannot handle a lot of power so it produces distortion if you try to play the music too loud, it probably would distort the low frequencies first as low frequencies require bigger cone travel.
  2. The amplifier output gets overloaded - if the chip (or the power supply) cannot produce enough current, then it will clip the waveform and produce distortion.
  3. Not enough voltage - 8 Ohm speaker needs 8VRMS to produce 8W of power. As you use a single supply and capacitor coupling, it means that the peak output of your amplifier is about half of the power supply voltage. So, to get 8VRMS (11.3Vpeak) the power supply as to be at least 22.6V, in practice it probably would need to be more than that because the output transistors in the chip drop some voltage. Otherwise there will be not enough voltage and the waveform will be clipped (the chip cannot have 14V on its output if the power supply is 12V)
  4. The amplifier input get overloaded - the input voltage is too high for the amplifier chip This is not very likely for your project, but I included it for completeness sake.

Buzzing

The input picks up the electromagnetic field from the mains wires inside your house and amplifies them as if they were useful signal. To reduce the hum, you should put the amplifier in a metal case to shield it. It would still pick up some hum when the input is not connected to anything (or worse, connected to a wire which is not connected to anything), but that is not really important.

Also, the hum could be coming from the power supply (if you use a non-switching power supply) if there is insufficient filtering (not enough capacitors).

Resistor in series

It will not work - putting resistor in series with the input you will just lower the volume while putting the resistor in series with the speaker will reduce the output power because you will be wasting some power on the resistor. The amp will just start clipping at lower volume.

My suggestion

Find out the power of your speaker. Connect it to another (more powerful) amplifier and turn the volume up until you hear distortion. Note if the volume is flouder than with your amp or not. If it is the same, then you need a more powerful speaker.

If the chip can survive it (read the datasheet), use a higher voltage power supply, especially if you want to use an 8 ohm speaker. Or find a 4 ohm speaker - it would need less voltage for the same power (if your chip can drive 4 ohm speakers).

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    \$\begingroup\$ 8W! Have you ever heard 8Weff indoors? Your windows will break. 1W is already loud. \$\endgroup\$
    – stevenvh
    May 26, 2012 at 11:10
  • \$\begingroup\$ @HarshaCAlva your input voltage is shown to be 6-18VDC. Please edit this in your question. \$\endgroup\$
    – abdullah kahraman
    May 26, 2012 at 11:15
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    \$\begingroup\$ @stevenvh No. You're using a "natural log of 2", but you should be using "natural log of 10". Also, we're talking about power, not "voltage" so you have to multiply by 20, not 10. So the real formula is 20*log10(2700W/1W) = 60 db, +80db = 148 dB. Another way to think of this is "+6db for every doubling of wattage". For 1024 watts, from 1 watt, you double the power 10 times, or +60db. Add 80 dB and you get +140 dB. 2048 watts=+146db, 4096 watts=+152db. This give you a theoretical max, actual max will be less (about +138 dB in my system). \$\endgroup\$
    – user3624
    May 26, 2012 at 16:09
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    \$\begingroup\$ @David - yes, that \$ln_2\$ was a lapsus. But you're wrong about the factor 20. For power it's 10, for voltage it's 20. see here. So that stereo of yours is only 124dB? Pretty lousy, isn't it? ;-) (I'll presume you have at least 90dB speakers, 80 is bad) \$\endgroup\$
    – stevenvh
    May 26, 2012 at 16:20
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    \$\begingroup\$ @stevenh, yes, 8W can be pretty loud, but only if the speakers are efficient. That being said, I have a pair of 25W speakers (quite loud) and 90W speakers (the woofer is 25cm), playing those at full power is really loud indeed. But no, to break good windows you need more than the 90W speakers at full power. Unless you can find the resonance frequency of the glass. \$\endgroup\$
    – Pentium100
    May 26, 2012 at 19:59
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You say you're using a 5V supply. The datasheet doesn't say in so many words, but the graphs don't show any values for supply voltages below 8V. Most probably it's your voltage which is too low.

enter image description here

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To avoid buzzing sound produce from the speaker when the 3.5 mm audio jack is not connect to the audio sources, I suggest that you should connect at least 330 ohm resistor between the input to the ground. This can release the buzzing sound from produced.

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I think you should use a higher voltages than 5 volts. Because I have made an amplifier using a TDA2002 and operate it using a 5 volts, it produce noise when the volume is louder. Then I try to use 9 volts power supply, 1200 mA/1.2A and the result is better than using a 5 volts. Mean, it not producing any noise.

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Da,este necesara o tensiune de alimentare mai mare,de cel putin 9Vc.c.,dar preferabila de 12Vc.c.,obtinuta dintr-o sursa bine filtrata,si in acelasi timp trebuie verificat si semnalul de la intrare,fiindca poate chiar el sa fie deformat/distorsionat sau insotit de zgomot-brum de filtraj.

Yes, it needs a higher supply voltage, at least 9Vc.c., but preferably 12Vc.c., obtained from a source well-filtered, and at the same time must be checked and the input signal, because maybe him to be warped / distorted or accompanied by humming noise-filtering.

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    \$\begingroup\$ Your answer may be helpful, but most people here can't read it. Please post in English. Raspunsul tau poate fi de ajutor, dar cei mai mulți oameni de aici nu se poate citi. Vă rugăm să post în limba engleză. (Romanian translation courtesy of google translate.) \$\endgroup\$
    – JRE
    Oct 12, 2016 at 9:37
  • \$\begingroup\$ @Nelu Postarile in limba romana nu sunt permise pe acest site. Postarile viitoare in limba romana vor fi sterse. Folositi, va rog, doar limba engleza.. [not google translated, so it would be clearer] \$\endgroup\$
    – m.Alin
    Oct 13, 2016 at 11:04

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