What weighs 21-lbs, takes up two rack spaces, and outputs 2. 400 watts If you said the dope I’ve been smoking, you’re off the mark. It is the QSC PLX-2402. The 2402 combines a high-efficiency class H amplifier with a QSC’s PowerLight switching power supply. Earlier attempts at power amplifiers with a switching power supply were greeted with a less than an enthusiastic response, as the power supply typically sampled at little more than twice the audible range, or at about 40-44kHz. This leads (usually) to a kind of muddy bass and harsh highs. The PowerLight circuit samples at 230kHz providing much better bass response, and a noted smoothing of the highs.