The way I see it is this: lets assume that your choice of a good solid speaker driver will take 250 watts rms and is 8 ohms impedance. Work out how many volts rms that is across 8 ohms. mulitply by 1.414 to get the peak voltage. Add ~5 to 10 volts and this gives you the total rail voltage your amp needs, half above zero and half below zero.

Now the next bit is my whole point - if you want more power, stick on another loudspeaker and another pair of output transistors (psu suitably rate of course). Ten times the power? Ten times the transistor capacity and ten times the speakers *all in parallel*. What's the point of building an amp that can swing absolutely whopping peak to peak voltages with the ridiculous demands that makes on transistors, and then find that most speakers won't handle that amount of drive voltage anyway? Just decide the maximum drive voltage that your favourite loudspeaker can handle and design your amp for this o/p voltage capability. More power = proportionally more transistors and more speakers all in parallel, the maximum output voltage always remains the same, only the current goes up.

GP.

GP.