I need to design experimental prototype of power amplifier (PA) for a horn speaker. The PA should support 100W RMS @ 8ohm. Power supply voltage is 12V. My first (and probably most simple) idea was to use PA integrated circuit such as TDA7294 (although it is targeted for Hi-Fi systems), not just because simplicity but also because of useful features like stand-by, thermal protection, short circuit protection... PA would be configured as a bridge in order to reduce required power supply voltage and get the proper power for the given impedance. However, this approach still requires step-up converter in order to produce required voltage (about +-25V). Maybe I can use some of the shelf converters (if can find proper for such voltage), but anyway want to avoid its design at this stage.
By searching for existing PA, I found some solutions with push-pull amplifiers with output transformer. I am not sure if my requirements can be achieved like this. In general, by boosting the output voltage with output transformer I compensate impedance limitation (with only 12V and 8ohm, maximal power is less than 18W). But this would require very low transformer primary impedance for the 100W power @ 12V (as the power should be the same of the both sides, assuming no loses). I haven't found such audio transformers. I am not sure if I am missing something. Also not sure if because transformer the back EMF is concern in order to protect other devices connected to the 12V rail.
What is you suggestion? What is optimal approach that should I follow?
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\$\begingroup\$ What does \$\color{red}{\text{100W RMS}}\$ actually mean? \$\endgroup\$– Andy akaCommented Apr 9, 2020 at 10:28
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\$\begingroup\$ You need a transformer - unless you can rewind the speaker for lower voltage or increase your supply V. Whether the transformer is before the amp (boost converter) or after it (audio output) is up to you - BUT a transformer that only has to work at one high frequency is MUCH smaller, cheaper and simpler to make than one for full range audio. In either case it's likely to be custom wound, so I'd go for the simpler route. \$\endgroup\$– user16324Commented Apr 9, 2020 at 10:34
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\$\begingroup\$ Why does this need to be a new design? That power level (and more) is already readily available in automobile audio systems. \$\endgroup\$– Dave TweedCommented Apr 9, 2020 at 10:40
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\$\begingroup\$ Yes, you are right, but because there will be also the other specific hardware, and the PA is just a part of the system. It should be integrated in the same unit. \$\endgroup\$– IgorEkisCommented Apr 9, 2020 at 10:45
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