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.
The output section uses a normally class AB linear output circuit with 8 output devices per channel. However, when needed, the power amp circuit can switch to a higher voltage rail. This allows the unit to maintain high-efficiency under most conditions, while providing all the power necessary when called for.The switching of voltage rails takes less than a millisecond, and is transparent to the user.The amplifier is nominally rated for 425 watts per channel into 8-ohms, 700 watts into 4ohms, and 1200 watts into 2-ohm stereo.
When bridged, the unit provides 1500 and 2400 watts into 8 and 4 ohms respectively. It features a variable speed fan cooling system, a soft clipping circuit, 1/4” unbalanced and TRS balanced inputs, as well as XLR balanced inputs. A low cut filter is also provided with a selectable 30 or 50 Hz cut off point. The 2402 also has the best S/N ratio of the line, with a respectable 108dB. Full bandwidth dampening factor is given as >500 into an 8-ohm load. The PLX series is meant for professional use, but it can easily find its way into a home hi-fi or HT setup, where a ludicrous amount of power is needed. A perfect candidate for a passive sub power amp, or even powering main or surround speakers. The specifications are at least as good as any receiver or power amp in its price range.
Now that we’ve gotten to it, the PLX-2402 is a good bargain. With used units in good condition typically fetching only $500-$600, it is an inexpensive road to high-power at only $0.20-$0.25 per watt. Brand new units can be had for little more than $250 more, when on sale.