About TDA7294

[Ziddik]

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good job drago, i want try this tda7294 circuit too but i want a few more informations about the mute/standby pins.. I think it needs a capacitor at output pin! Or the ic may" fry" since the GND passes through speaker coil to output pin, ain't it necessary?

 

[Dragon Tamer]

Add a series resistor with the load. I don't think a capacitor was used because the output voltage swings between +V and -V, a normal polarised cap would explode. You can add a cap as long as it is rated for at least 3V above the total voltage (with a +30, -30 supply that would be 60V). Then just connect the speaker to the negative supply terminal.

 

[audioguru]

I think it needs a capacitor at output pin! Or the ic may" fry" since the GND passes through speaker coil to output pin, ain't it necessary?

The output is 0V at idle and it averages 0V when the signal causes the output to swing positive and negative because the IC has a positive and negative power supply. Then an output coupling capacitor to the speaker is not required.

 

[Ziddik]

but one of the speaker terminals is connected to output pin of the IC and other one is connected to GND! not to "negative supply".. Am i right guys?.. And i was meant to add a capacitor between output and speaker!..

 

[audioguru]

but one of the speaker terminals is connected to output pin of the IC and other one is connected to GND! not to "negative supply".. Am i right guys?

Yes, one speaker wire is supposed to connect to GND. If you use an output coupling capacitor and connect one speaker wire to the negative power supply voltage then the speaker will produce severe hum from the ripple on the negative supply when the output power is high.

 

[audioguru]

in the updated schematic the positive + supply connected to mute/stndby pins through a 10k resistor! Is that all right?

the datasheet has the resistors shown and an explanation and graphs that the Mute and Standby are driven from logic with a 5V supply.

 

[Ziddik]

thanx.. I am gonna try this circuit.. Do u guys have anything more (warning or..etc)to tell me about the schematic? .. I have to build a subwoofer amp for my friend..

 

[Ziddik]

STK ics are very very very expensive here