Patent ID: 7417502

Claim:
A selectable power supply for use in a thermionic vacuum tube audio amplifier comprising: a power transformer having a first secondary coil for providing a first AC power voltage with a first volt-amp rating and a second secondary coil for providing a second AC power voltage with a second volt-amp rating that is different from the first volt-amp rating; first rectifying means coupled to the first secondary coil for converting the power to a first rectified DC plate voltage, second rectifying means coupled to the second secondary coil for converting the power to a second rectified DC plate voltage, filter means coupled to the first and second rectifying means for reducing the ripple component of one of the first or second rectified DC plate voltage to thereby present DC plate voltage adapted to supply at least one vacuum thermionic element of an audio amplifier; and user-selectable switch means for selectively interrupting the rectified DC plate voltage presented at the filter means.