TDA7297 problems

Thread Starter

duykwe

Joined Nov 17, 2023
71
Hello everyone, I am new here. I have a TDA7297 15W+15W audio amplifier. I use the default schematic in the datasheet to make it. And I use a 10W 8ohms speaker. But the problem is when I measure the power of the speaker, it's only 3.3W (6.6V, 0.5 A max). Do you guys know why is that, and how to fix it? Also, I would be really grateful if someone give me some advice to improve the quality of the sound. Thank you guys so much.
 

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sghioto

Joined Dec 31, 2017
5,369
What is your supply voltage?
Output Power is equal to the voltage across the speaker squared divided by the speaker impedance, should be appx 5.5 watts at 6.6 volts.
 
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sghioto

Joined Dec 31, 2017
5,369
If the power is only 3.3 watts then the speaker impedance is 13.2 ohms not 8 ohms if the voltage is 6.6 volts.
What was the input signal and frequency used to determine the output?
How was the .5 amp measured?
 

Thread Starter

duykwe

Joined Nov 17, 2023
71
If the power is only 3.3 watts then the speaker impedance is 13.2 ohms not 8 ohms if the voltage is 6.6 volts.
What was the input signal and frequency used to determine the output?
How was the .5 amp measured?
First I use a VOM to measure the speaker alone, its impedance is 7.3 ohms. The input for the IC is a jack of 3.5mm that is plugged into my laptop. When I play the music, first I check the voltage at the speaker compared to common, it says 6.6V, then I switch to the DC Ampere measurement and put the black pin connected to the output of the IC, the red pin connected to the speaker positive input. And then read the values and go up down from 0.2 - 0.5 A.
 

sghioto

Joined Dec 31, 2017
5,369
first I check the voltage at the speaker compared to common, it says 6.6V,
Not sure about this. Are you reading a DC voltage from one of the speaker outputs to ground meaning the negative side of the 12 volt supply?
BTW that photo of the wiring is a disaster, where's the chip?
The proper way to measure output power is to use a 8 ohm resistor rated a minimum of 10 watts to simulate the speaker. This is called a "dummy load". The input signal should be a steady 1000hz sine wave with enough amplitude to drive the output of the chip to clipping. An oscilloscope is required to view and measure the AC voltage output of the chip just below the level that clipping starts.
 

MrChips

Joined Oct 2, 2009
30,475
Hello everyone, I am new here. I have a TDA7297 15W+15W audio amplifier. I use the default schematic in the datasheet to make it. And I use a 10W 8ohms speaker. But the problem is when I measure the power of the speaker, it's only 3.3W (6.6V, 0.5 A max). Do you guys know why is that, and how to fix it? Also, I would be really grateful if someone give me some advice to improve the quality of the sound. Thank you guys so much.
Why are you so concerned with measuring power output?
6W output is not twice as loud as 3W output. The difference is only 3dB.
 

Thread Starter

duykwe

Joined Nov 17, 2023
71
Not sure about this. Are you reading a DC voltage from one of the speaker outputs to ground meaning the negative side of the 12 volt supply?
No, I mean ground here is they are all connected compared to the Vin (12V), so when I read from one of the speaker outputs, 6.6V compared to 0V. Also, I tested the other side of the speakers, and it's nearly the same.
BTW that photo of the wiring is a disaster, where's the chip?
Sorry for that, I uploaded the pictures again.
I'm sorry for that, here are the full view of it. Tell me if something is not clear.
The proper way to measure output power is to use an 8 ohm resistor rated a minimum of 10 watts to simulate the speaker. This is called a "dummy load". The input signal should be a steady 1000hz sine wave with enough amplitude to drive the output of the chip to clipping. An oscilloscope is required to view and measure the AC voltage output of the chip just below the level that clipping starts.
I don't have the oscilloscope, but this is so helpful. Thank you so much for your dedication in your comment.
 

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Thread Starter

duykwe

Joined Nov 17, 2023
71
Why are you so concerned with measuring power output?
6W output is not twice as loud as 3W output. The difference is only 3dB.
As you say, I looked for the Sound Power Level and did a bit of calculation. Then I got the result is appx 2.6 dB which says that it's not as loud as twice. This is really great knowledge. Thank you so much
 

sghioto

Joined Dec 31, 2017
5,369
No, I mean ground here is they are all connected compared to the Vin (12V), so when I read from one of the speaker outputs, 6.6V compared to 0V. Also, I tested the other side of the speakers, and it's nearly the same.
That's what I thought you were measuring. You need to measure the AC voltage across the speaker using a sine wave signal.
Go on line and find "Test Tone Generator". Set the frequency for a 1000hz sine wave and use this for the signal input.
Since you don't have a scope all you can do is crank up the volume until the level is just below any noticeable distortion and measure the AC voltage across the speaker.
 
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