problem with tda7294

Chaom1 · 5th January 2006, 11:39 AM

Hello

I have a little problem with my 2xtda7294 amplifier i just made.
I have to give it input at least 2-3v to get output 20v.

Maximum output i have got is 21v, then the input was 3.5v

So I dont know what is the problem - it should give 30v with 1v input at least. My power sypply is +-32v.

The schematic I used is here: http://www.masterkit.ru/main/set.php?num=540
http://www.masterkit.ru/info/magshow.php?num=48

Of course there is a possibility to lower the r1 (680ohm) to lets say 200 ohm and then rise c3 from 22mkf to 100mkf to save the bass responce. But I kinda dont wanna do that, something must be incorrect about this circuit.

Maybe someone can help me.

thanks in advance

moamps · 5th January 2006, 11:56 AM

Quote:

Originally posted by Chaom1
[B]Maximum output i have got is 21v, then the input was 3.5v

Hi,
did you check the waveform at the output?
How did you measured the in and output voltage?

Quote:

So I dont know what is the problem - it should give 30v with 1v input at least. My power sypply is +-32v.

Yes. But for 30VRMS at the output, you need almost +/- 50V voltage from your power supply.
What's the output voltage for 0.5V at the input?

Regards,
Milan

Chaom1 · 5th January 2006, 12:12 PM

I didnt check the waveform
In and output voltage I measured with usual tester. Output had 6.8ohm 5w resistor in water.

with 0.5v input it has output something 5-7v

Chaom1 · 5th January 2006, 12:21 PM

but in datasheet there is also capactor there, and in every circuit in the web. If I remove it, i will loose low frequency, the links says. And i have stereo amp and different 100pf capacitors, so one of two should be working great anyway.

but both of the channels act the same...

lineup · 5th January 2006, 12:33 PM

What frequency did you use?

Many AC voltmeters can not show good numbers at 1000 Hz
If you do not have a special AC voltmeter,
try using 200 Hz or something like this.

Chaom1 · 5th January 2006, 02:35 PM

I used my soundcard and later old fm-radio.
Well, im certain that something is wrong since i havent seen an amplifier before what plays 1/3 of its power with my soundcard.

the output is about 700mv.

later the radio output was already 2-3v

sagarverma · 6th January 2006, 03:37 AM

remove arrowed cap in the image im posting.
its not there in standard schematic.

+

dont rely on dmm.for as lineup says,dmm response is poor for high frequencies.

Chaom1 · 6th January 2006, 12:33 PM

thanks, gonna try it.

5th January 2006, 11:39 AM	#1
Chaom1 diyAudio Member Join Date: Nov 2004 Location: Estonia	problem with tda7294 Hello I have a little problem with my 2xtda7294 amplifier i just made. I have to give it input at least 2-3v to get output 20v. Maximum output i have got is 21v, then the input was 3.5v So I dont know what is the problem - it should give 30v with 1v input at least. My power sypply is +-32v. The schematic I used is here: http://www.masterkit.ru/main/set.php?num=540 http://www.masterkit.ru/info/magshow.php?num=48 Of course there is a possibility to lower the r1 (680ohm) to lets say 200 ohm and then rise c3 from 22mkf to 100mkf to save the bass responce. But I kinda dont wanna do that, something must be incorrect about this circuit. Maybe someone can help me. thanks in advance

5th January 2006, 12:33 PM	#5
lineup diyAudio Member Join Date: Dec 2005 Location: the north	What frequency did you use? Many AC voltmeters can not show good numbers at 1000 Hz If you do not have a special AC voltmeter, try using 200 Hz or something like this. __________________ lineup

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5th January 2006, 12:12 PM	#3
Chaom1 diyAudio Member Join Date: Nov 2004 Location: Estonia	I didnt check the waveform In and output voltage I measured with usual tester. Output had 6.8ohm 5w resistor in water. with 0.5v input it has output something 5-7v

5th January 2006, 12:21 PM	#4
Chaom1 diyAudio Member Join Date: Nov 2004 Location: Estonia	but in datasheet there is also capactor there, and in every circuit in the web. If I remove it, i will loose low frequency, the links says. And i have stereo amp and different 100pf capacitors, so one of two should be working great anyway. but both of the channels act the same...

5th January 2006, 02:35 PM	#6
Chaom1 diyAudio Member Join Date: Nov 2004 Location: Estonia	I used my soundcard and later old fm-radio. Well, im certain that something is wrong since i havent seen an amplifier before what plays 1/3 of its power with my soundcard. the output is about 700mv. later the radio output was already 2-3v

6th January 2006, 12:33 PM	#8
Chaom1 diyAudio Member Join Date: Nov 2004 Location: Estonia	thanks, gonna try it.

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