Sumo Andromeda power amplifier 1984 Measurements

Sidebar 1: 1984 Measurements

The Andromeda measured less than 0.028% Total Harmonic Distortion plus Noise (THD+N) at its rated power into 8 ohms, and less than 0.053% THD+N into 4 ohms at 324Wpc. The amplifier could not produce more power at 4 ohms, going into mutual conduction when pushed further. (Mutual conduction occurs when the complementary output devices (which normally work in turn) conduct current simultaneously, and thus work against one another, behaving like a partial short circuit across the power supply.) This was evidenced by a sudden increase of current draw, which suddenly jumped from 15 to 25 amps. This condition is unlikely to occur when playing music, but the measurement does indicate a failure of the amp to meet its specs.—David Clark