As a power amp, I know the PS at 8ohms is 50 watts…
but at 4ohms is there an increase of wattage?
Hey T-man
The PS-2A is 50W into 4 Ohm, 8 Ohm or 16 Ohm because it has an output transformer that impedance matches the speaker to the tubes.
I am going to try my best to channel Steve… cue the car analogy!
When you are driving at 40 mph, 80 mph and 160 mph the car engine is cycling at more or less the same revolutions per second (probably somewhere between 1000-3000). How is that? Well, to drive faster, you need to shift gears. The gear box is impedance-matching the engine speed to the wheel speed for maximum power transfer in each case.
The output transformer plays the same role, it is impedance-matching the output power to the different driving conditions loads.
This happens with solid-state amplifiers but not tube amps. A solid-state amplifier can deliver more current the smaller the load impedance. The same voltage is delivered in all cases. So voltage x current product (i.e. Power) is higher for small loads.