An Interesting Experiment about Audio Amplifier

  1. victory
    According to the TDA7294V Datasheet,TDA7294V is an integrated, monolithic, Class AB audio amplifier designed specifically for Hi-Fi applications.It has low noise, low distortion, good ripple rejection and can be operated from a wide range of supply voltages with a DMOS output stage and can deliver 100W RMS into an 8Ohm speaker at +/-38V dual supply.Please look at the following circuit diagram:
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    TDA7294 is configured to provide 100W output power into an 8Ohm loudspeaker at +/- 38V supply. C8 is the input coupling capacitor and the input is applied to the non-inverting input (Pin3) of the IC. C3 and C9 are power supply filter capacitors while C10 and C4 are bypass capacitors. C2 is the bootstrap capacitor. RC network comprising of R1 and C1 improves the high frequency stability of the amplifier and also prevents oscillations. R2 and C6 sets the mute time constant while R3 and C5 sets the standby time constant. S1 and the mute switch and S2 are the standby switch. R5 is the input resistance and the amplifiers input impedance has a direct relationship to its value. R4 and R6 is used for setting type closed loop gain and with the used value, gain is 30dB. C2 is a feedback capacitor and it also provides DC decoupling.

    Well,I have spent some time -nights- with 7294 according to the following description to asking it for 100 watts. It totally refused to do so.

    +/- 24 V at the rails you get 25 W over 4 Ohms – and that’s it. Higher voltage, more load (<4 Ohms) – you always get 25 Watts. This IC blushes in stage fright.

    But I was successful: ST itself offers a much more sophisticated circuitry in their datasheet and i managed to build it and to make it yell 110 Watts over 4 Ohms.

    But do I really need this kind of minstrel show:

    +/-25 V AND! +/-50 Volts, added eight transistors and so on? Everything well painted on a double layer pcb postcard?
     

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