Actually yung sinabi ni rubis is already right-on. Power through the power plug is much higher than power out of the speaker terminal. This is because tubes use heaters, which are very power hungry, but whose consumption don't figger out in the speaker terminal. Like a single 12AX7 should be allocated 300mA of heater power, each. So for instance like the 50 Watter I'm assembling, if I did go all tube, I'd need a 2A transformer, just for the heaters. For 100W, ok na mga 5 Amperes. Heater pa lang yun, hindi pa kasama yung power na gagamitin to actually amplify the signal.