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precedent
Starting Member

China
1 Posts

Posted - 06/22/2017 :  02:11:31 AM  Show Profile  Reply with Quote
Hello~all

I would like to ask you some suggestions about my audio amplifier. Itís my first time to finish an electronic project by myself. But there are some troubles occurred caused I am not professional.

I have made an audio amplifier based on TDA7294 for my hom stereo. As the she schematic diagram shows: The TDA7294 is configured to provide 100W output power into an 8Ohm loudspeaker at +/-38V supply. According to the datasheet of TDA7294( http://www.kynix.com/uploadfiles/pdf8827/TDA7294V.pdf ), it is a monolithic integrated circuit in Multiwatt15 package,intended for use as audio class AB amplifier in Hi-Fi field applications. So I am ensure that the TDA7294 is suitable for my project. I have also checked the other factors like the power supply,voltage range, ripples and so on. All the signals at the individual pins are correct just that there isnít any output signal at pin14. But it doesnít work at all. I couldnít understand what could be the problem?
Could anyone here help me?
Appreciate it a lot !

BLH
Advanced Member

5636 Posts

Posted - 06/22/2017 :  03:23:47 AM  Show Profile  Reply with Quote
On your power supply. It is a split supply with a positive negative and common point output?
+ on +VS, - on -VS and the common supply on the ground?

When running.
What is the voltage feeding the VM and VSTB inputs?
How are VM S1 and VSTB S2 set?

Edited by - BLH on 06/22/2017 03:54:42 AM
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Geo
Advanced Member

Canada
741 Posts

Posted - 07/03/2017 :  4:29:11 PM  Show Profile  Reply with Quote
Assuming the chip is wired correctly, there isn't much to go wrong. As BLH suggests, make sure the power supply has the center connected to the ground. Otherwise it'll be floating. Just as well, wrong setting of the VM and VSTBY inputs could prevent it from working.
Don't forget you may have blown the chip - it takes a split of a second, especially at high voltages like these.

GJN
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Geo
Advanced Member

Canada
741 Posts

Posted - 07/03/2017 :  4:42:12 PM  Show Profile  Reply with Quote
One additional comment: The data sheet says 100W music power. This is rather misleading, going back to the nineteen-sixties competition among amplifier builders. They introduced three types of output power - RMS, Peak power and Music power.
RMS is the only true power. Peak power and Music power base their ratings on the fact that in music power peaks are not continuous but occur at different times. How they differ from the RMS rating depends on the type of the power supply and especially the size of its storage capacitors (C3 and C9 above). Generally, 100W Music power would correspond to about 25W RMS. Some manufacturers of stereo amplifiers would have claimed 200W Music power because there were 2 channels.

GJN
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