0.25W when the supply is 6V is a very small output power. With a 5V supply it is less, maybe only 0.14W. That is the output with no distortion, if you turn up the volume it will be clipping with severe distortion.

The 100k resistor you added to its input pin 1 then to ground also causes distortion.
Please post your detailed schematic.

 

For a 5V supply you should try using a PAM8403 class-D stereo amplifier IC. Its output will be 2.5W per channel into 4 ohm speakers with low distortion or will be 1.4W into 8 ohm speakers. Its class-D does not waste battery power making heat like ordinary older amplifiers.

 

How can

5V supply? The TDA2003 has a minimum supply of 8V because some of them or all of them do not work with less voltage.
The datasheet shows the maximum output power dropping as the supply voltage drops and at 6V I calculated an output power of only 0.25W into 8 ohms if it works. With your 5V I doubt it works.

I am quite impressed by this performance. Is there any way you can post the amplifier circuit and let us know the voltages of the power supply? That could be a very useful circuit to use for some of my applications.

for voltage rating see TDA2003 datasheet, I added 10K Pontentiometer myself

 

How can


for voltage rating see TDA2003 datasheet, I added 10K Pontentiometer myself

I have experimented with some circuits using various amplifier modules and ICs and most do not work properly below the published minimum voltage. Not just weak, but huge distortion and with some, instability as well. So the supply voltage is quite important. Most of the unregulated 5 volt supplies will deliver close to 8 volts at no load, and then drop as current is drawn. So really, there is no point in even trying to use the TDA2003 at less than 8 volts. 12 volt wall warts are common enough.

 

This amplifier is working but its overheating too much at 12v supply, then I use 5v supply, still its overheating but not that much, but so soon I switched it on

View attachment 210290.

the over-heating problems is caused by the 2.2Ohm and 1Ohm resistors which I used 10Ohm in their places or what that I cant figure out?

https://www.parts-express.com/FootNote-Electric-Guitar-5-Watt-Amp-Assembly-No-Power-Supp-249-402 - great little amp board for only 9 dollars and https://www.parts-express.com/6-1-2-Poly-Cone-Woofer-4-Ohm-299-609 for $6.98 and sounds great.

 

This amplifier is working but its overheating too much at 12v supply, then I use 5v supply, still its overheating but not that much, but so soon I switched it on

View attachment 210290.

the over-heating problems is caused by the 2.2Ohm and 1Ohm resistors which I used 10Ohm in their places or what that I cant figure out?

They do not show it in the Datasheet but using an Op-Amp Preamp will really drive these amps and the kits can be purchase with volume,bass,midrange and treble control.

 

The Footnote Guitar Amplifier uses 2 of the TDA2003 Transistors - the Guitar Transistor is driven by a LM4558 Operational Amplifier with volume bass and treble controls and the Auxiliary Input uses another LM4558 driving another TDA2003 and the input device controls the output on this amplifier circuit plus cable tester and eight 9V power outputs for foot pedals.

 

As I look at the circuit assembly drawing I did not see any capacitor across the supply connection. So some of the overheating may be due to oscillation, which will be at a frequency far to high to hear, but the strong oscillation will cause a great deal of power dissipation.
If you look at the application circuit you will see both a 100 MFD and a 0.1 MFD capacitor across the supply connections.
AND, why would you expect it to operate correctly when you do not have the correct values of resistors in the circuit. That is a real puzzle. Especially in the feedback circuit and the oscillation prevention parts of the circuit. Part values DO MATTER..

 

The Footnote Guitar Amplifier uses 2 of the TDA2003 Transistors - the Guitar Transistor is driven by a LM4558 Operational Amplifier with volume bass and treble controls and the Auxiliary Input uses another LM4558 driving another TDA2003 and the input device controls the output on this amplifier circuit plus cable tester and eight 9V power outputs for foot pedals.

The TDA2003 IS NOT a transistor! It IS a complete power amplifier integrated circuit.

 

I used 5v supply from the main

Is this a ready made 5 volt supply? Any details?

 

The wrong resistor values cause the antique amplifier to oscillate at a high frequency that causes it to overheat.
The datasheet of the original ST Micro TDA2003 and the Chinese Youwang UTC2003 copy say that.

 

Is this a ready made 5 volt supply? Any details?

It does not mmatter, as far as the oscillation goes, if this amplifier has even the best external power supply or a cheap one. The resistor values must be fairly close, and those two capacitors on the 12 volt supply must be close to the amplifier. The capacitor connections need to be physically close to the amplifier IC.
The reason is that the impedance of the connection wires rises with frequency and so it coauses feedback between te amplifier stages.
This is seldom covered enough in engineering classes.

 

It does not matter, as far as the oscillation goes,

I wasn't talking about any oscillation. The TS said the amp was working OK with a 8 ohm speaker but not good with a 4 ohm.
Maybe because the 5 volt supply cannot deliver enough current.

 

The amplifier is stable with a voltage gain of 1 + (220 ohms/2.2 ohms)= 101 times. It is unstable with a voltage gain of 1 + (220 ohms/10 ohms)=23 times.
It oscillates with an inductive load so the zobel network at the output must have a 1 ohm resistor and it oscillates with 10 ohms.
The LM1875 amplifier is similar to the TDA2003 and its datasheet also says its minimum allowed gain and it has the same 1 ohms zobel network to avoid oscillation.

We do not know if the old TDA2003 amplifier has a heatsink.

 

A VERY good point about the heat sink. This is a linear amplifier, and so we do only have almost 70% efficiency. That leaves 30% of the input power as heat. So certainly a heat sink is mandatory if al is perfect. And it needs to be an adequate heat sink.
So one more question: How big is the heat sink on the TDA22003 ???

AND worse yet, for some folks 10% distortion is OK. With some of the stuff I hear, 15% distortion would not be noticed..

See Also the following post by PrairieMystic:

 

Late to this thread, but TDA2003 is difficult to get stable and similar to the LM1875. The IC can be hard to tame. Adding ~220pF cap across the feedback resistor helps a lot i.e. for a 13k feedback resistor 220pF cap gives 56kHz, or 20k resistor a 36kHz rolloff. This alone has always worked for me. I'm assuming a dual supply circuit, not the single-supply.
Single point grounding whereby the loudspeaker (-) is grounded at the power supply (not at the IC) is also essential. I also add an input RC filter to stop RF/AM radio from getting in, rolling off the input say 2k2 and 1,000pF for around 72kHz.
The IC does oscillate around 10-12MHz (16MHz LM1875) so 0.1uF disc or film caps on the +V and -V are also needed because the power supply falls apart at 10MHz if it's only got electrolytic capacitors present.
The circuit is sensitive to layout and grounding and not really a simple project without a good pc board.

 

A VERY good point about the heat sink. This is a linear amplifier, and so we do only have almost 70% efficiency. That leaves 30% of the input power as heat. So certainly a heat sink is mandatory if al is perfect. And it needs to be an adequate heat sink.
So one more question: How big is the heat sink on the TDA22003 ???

AND worse yet, for some folks 10% distortion is OK. With some of the stuff I hear, 15% distortion would not be noticed.

A linear amplifier runs cooler when its output is clipping with squarewaves.
Very high frequency oscillation heats an amplifier a lot because it smooths the squarewaves into linear sinewaves.