A: The Orange Dual Terror (which is a two-channel amp with a Tiny Terror channel and a Fat channel) has four EL-84 power tubes. As you noted, the front panel switch provides full power, standby, and half power settings. But the “secret” is the switch on the back, which turns off two of the power tubes.
With four power tubes on, the front-panel switch changes the amp from 30 watts to 15 watts. With two power tubes on, the front-panel switch changes the amp from 15 watts down to 7 watts.