Power supply for TDA7294 100w Amplifier


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the datasheet says

Later it says the absolute maximum supply is to be less than ±50V when no signal is applied.

The highest transformer voltage you can use is approximately 27-0-27Vac
Depending on your mains supply voltage and tolerance and on the transformer regulation you may find that your maximum transformer voltage can be anywhere from 25.5-0-25.5Vac to 28-0-28Vac
You could drop those few extra volts with a capacitance multiplier or basic regulator circuit that can give out at least an average of whatever Ipeak into 4 ohms is (starting point for worse case average current and allowing for impedance dips). A reasonably hefty capacitor after either (>1,000uf) is still required though to handle current peaks. As long as it CAN handle your worse case current demands the regulator need be nothing fancy. A simple zener referenced emitter follower would work wonders.
This might well be obvious, but I thought you wanted to save your transformer which after all is the expensive bit!
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The Micromega AMP 3 ( tda 7294 + power transistors) , works pretty well at +/-40 v under 4 or 8 ohms load , I run bi-amp with two of these nice amps , and my speakers are 4 ohms ;-)

the datasheet is clear +/- 40 v is the upper limit for the 7294 , and +/- 50 v for the 7293 , so 7293 is your only choice ;-)

Unless regulating the supply rails you must at least also take into account +10% mains voltage taking for example +/-50VDC supplies up to +/-55V. This transformer you are trying to use it may be said is just too large for chipamps! Keep it and make a good discrete subwoofer amp (or similar) later. For chipamps, follow Fabrices' or earlier suggestions for lower voltage transformer!
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I made TDA7293 Amplifier


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