Yes, 25 sounds about right.
Thanks a lot, so it is about 25Vpp out pr channel?
Does that not sound as about 36W out?
EDIT: the transformer are 26V-0V-0V-26V on the schematic, it is about 80W out, why?
What's the load impedance?
For a sine wave, the RMS power is equal to half the peak power, so with a 4Ohm load: P = V2/(2R) = 252/(2*4) = 625/4 = 78W.
A 26V transformer will output 36V, after losses in the rectifier, so 25V peak out seems reasonable.
I doubt it'll be able to output full power continuously, as the smoothing capacitors aren't big enough, but the output transistors will probably overheat too, at that power level. It's also not a problem, since peak power occurs typically less than 10% of the time, even at full volume.
Ehm, well better is the use to divide the rail voltage (which is the peak voltage of the sine wave) by the square root of two (= 1.41).
Which is obviously the same as the Rms value of the AC voltage (minus some losses), so in this case 26Vrms.
(26^2)/8 = 85W @ 8ohm or 170W @ 4ohm (the rail voltage is 26 * 1.41 = 36.7V)
However, with Class-AB amplifiers it's not uncommon to give a lot more headroom in the rail voltage.
The efficiency of a AB stage is about 60-70% at most, so that means that transistors will dissipate around 50W @ 4ohm.
That's quite a lot, so that makes me think, including the low amount of capacitive storage, this amp is suitable for 8ohm or higher.