TDA2003 Car Audio Amplifier

[rosmawati]

Hi,

I need to ask a question regarding car audio amplifier.
Actually I want to connect an audio amplifier so it can amplify any signal coming from my GSM module which 8 Ohm impedance and what I did was connect the differential line LOUD1 and LOUD2 to the input of the amplifier. As LOUD1 to the non-inverting and LOUD2 to inverting input
Nothing came out except those irritating noise when connected to the GSM module.
The amplifier module amplifies good sound when I connected it to mp3 player.
Did I choose the wrong amp IC?
Any please help me.:-(

 

[pranam77]

Hi, I need to ask a question regarding car audio amplifier.Actually I want to connect an audio amplifier so it can amplify any signal coming from my GSM module which 8 Ohm impedance and what I did was connect the differential line LOUD1 and LOUD2 to the input of the amplifier. As LOUD1 to the non-inverting and LOUD2 to inverting input. Nothing came out except those irritating noise when connected to the GSM module. The amplifier module amplifies good sound when I connected it to mp3 player.Did I choose the wrong amp IC? Any please help me.:-(

Have a look at the datasheet of the device here
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXutuqt.pdf
Youl'll find an application circuit where Pin 1 is an input pin where the audio must be fed. Similarely find which pin of the module (Loud1 or Loud2 )is connected to the ground (Negetive). Connect that pin to the negetive of the amplifier whereas other is the live pin with audio which can be connected to the audio IN pin of the amplifier. But naturally when GSM communictaes, you'll have disturbances in audio amplifiers. Then solution is to shield the audio amplifier or separate it from the GSM module with a shielded wire.

 

[rosmawati]

Hi Pranam77,

Thank you for your reply.
I tried to connect the amplifier input pin to the single ended output of the GSM module. This time around I captured voice signal but it was kindda mix with noise.
Do you have an idea how to reduce the noise?
One more thing, is it normal to have 1.14V DC at pin 1 amplifier pin after AC decoupling capacitor C1?

 

[kabiru]

I dont think you will find any voltage at the input but simply visit this link. hobby-hour.com/electronics/tda2003-power-audio.php/

 

[rosmawati]

Kabiru,

I followed the link u gave me but the informations is too sparse.

 

[kabiru]

Hi,can you upload the circute diagram you are using?

---------- Post added at 08:42 ---------- Previous post was at 08:41 ----------

Hi,can you upload the circute diagram you are using?there are many amplifier circute diagram you can used for your car stereo.

 

[dr pepper]

Unfortunately you cant just use the chip on its own, what you tried sounds like you connected the device up without feedback, so a very high gain amplifier will result causing the noise.
You will have to construct a bit of a circuit including feedback and bootstrapping.
Have a look at this circuit, its a minimal amp, the 2 capacitors at the top of the drawing are placed close up to the chip, and are meant to stop oscillations and other nasties, this circuit should work well.
RX is 39 ohm, and CX is 33nF.

 

[rosmawati]

Kabiru,

I use below reference circuit.



Dr. Pepper,

What if I use different value for Rx and Cx? And one more, I still picked up 1.14V DC at pin 1? Was that normal condition?

 

[dr pepper]

The above circuit will work fine, the values are slightly different and the sound might be very slightly different but it'll work.
The dc value you have at pin 1 is probably just the internal bias for the input on the chip, its possible that c1 is leaking you could replace it if it worries you, but its probably fine.
You say you have noise, and re-reading your op I see its connected to a 'phone, try getting a couple of suppressor torroids about a inch diameter and wrap the power and audio input leads a couple of turns round each one to remove any rf from getting into your circuit.

 

[kabiru]

Yes,the voltage at pin1 can be an internal biasing to the input and it has no any effect to the function of the amplifier the circute is ok,for you to confirm it just connect a pulldown resistor to the input and take the readings again.the noise you are getting at your output is due to noise from your hand set you can changed the value of C1 to a higher value and see the effect.

---------- Post added at 09:28 ---------- Previous post was at 09:22 ----------

Yes,the voltage at pin1 can be an internal biasing to the input and it has no any effect to the function of the amplifier the circute is ok,for you to confirm it just connect a pulldown resistor to the input and take the readings again.the noise you are getting at your output is due to noise from your hand set you can changed the value of C1 to a higher value and 0.1uf to ground and see the effect.