By MarkAmundson
When performing my ritual paces at the 2006 NAMM show, one of my highlights of the show was the new PLX2 series of audio power amplifiers from QSC. Having been an early adopter of high-powered, lightweight amps since the days of the Carver PM-1.5 in- troduction, I knew the PLX2 introduction was going to give QSC’s competition something to worry about. QSC provided me a PLX3602 and a PLX1804 to do this road test review.
The Gear
Having had QSC PowerLight amplifiers in my racks for quite a while, I have seen the nu- ances of features,all coming off the same man- ufacturing line in Costa Mesa, Calif. The new PLX2 is a retool-
ing of the
line, plus brand newc h a s - sis cosmetics that went from greys to lighter metallic front panels. From the original PLX front panel we lost one bar-graph LED per channel to the beefier looking panel metal and shrunk the gain controls a bit, but got a bit more exhaust venting to ease our cooling fears.
The rear panels got a minor simplification, replacing the mini 10 rocker switch with a sim- pler and slightly more flexible group of six slide switches in the new PLX “02” models (the PLX 1802, 2502, 3102, 3602). With these new switches you can even configure a 100Hz bi-amp setup by selecting paral-
lel mode and choosing which channels get the low or high pass filtering
And of course the big “what’s new” is the PLX“04” models (the PLX1104 and 1804).An example of design innovation, the 04 series has eliminated 2-ohm capa- bility. I like this because I believe running an amp at 2-ohms is a bad idea operationally. And, by building an amp to drive 4-ohm or higher impedance speaker loads, QSC was able to achieve this amp’s smaller size, lighter weight
and lower cost (all of which I like, too).
The PLX1104 and PLX1804 are two-rack- space stereo-channeled amplifiers with just
10.1inches of total rack depth, including the rear rail support ears. This means a bit less heatsink aluminum for the amplifier’s power transistors, but the amplifiers can do with- out it. At 550 watts (PLX1104) and 900 watts (PLX1804) per channel EIA rated at 4-ohms, one wonders what could have been possible at Woodstock if a PLX 04 amplifier had been available to replace the four 250 watt tube am- plifiers used at that gig.
But something had to be lost in the 04 models to keep the size, power capability and weight specifications impressive. Only NL4
Speakon connectors are available on the PLX1104 and PLX1804, and the slide switches are missing for basic stereo-in and unfiltered inputs for the TRS and XLR inputs. While the missing bind- ing posts made my swapping a PL218 for a PLX1804 a bit more of a chore in my amp rack, at least the additional Speakon connectors are better than stuffing unruly stranded speaker wire in the side orifices of the binding posts.
The Gigs
The first tests of the PLX3602 and PLX1804 amplifiers were done as stand-in monitor wedge and mains amplifiers for some quick and dirty small club gigs. Running full range for both wedges and tops all night long over the weekend, the musicians were shaking their heads how such compact amplifiers could drive so much loudness that previously would taken a full amp-rack to do. And with the pair weighing in at 34 pounds together, the load-in and load-out were made all that easier. While I could not quantify it, I felt that the PLX2 am- plifiers sounded cleaner, had more perceived power and gave off less heat than their original PLX models.
Back at the shop, I installed the PLX3602 and PLX1804 into the mid- and high - amplifier positions of my mains amp rack, and proceeded to give the amp
rack and my EV QRx speakers (QRx212 tops, QRx218 subs) a workout with the SMAART
Live software keeping score.I pulled a PLX3402 and a PL218 out of the mid- and high-amp positions, and checked the differences. The first thing that I had to do was back off about 4dB on the speaker processor to the PLX3602 as the original PLX amps were are 32dB gain units, and the PLX3602’s 35.9dB gain had to be tamed. The 32.5dB gain of the PLX1804 was close enough to get a pass on any high band speaker processor changes.
In a shop test scenario using CD tracks the
new PLX amps again seemed to put out less heat, and meet or beat the original amplifiers on sound fidelity. Swapping the PLX3602 into subwoofer duty also showed that it slightly out-classed what a PLX3402 was capable of, and was thoroughly capable of pumping out the lows to its 1250 watt at 4-ohm limit.I would have no fear of taking a bunch of PLX3602s out to do some heavy subwoofer work at a gig.
Out at a medium size club gig (300 per- sons), the PLX2 amps purred along without any problem, and never had to go beyond my “to the limits” testing I did in the shop. Look- ing for nits on these amplifiers for this road test review, the best I could do was whimper about the variability on gains on each model, and the shrinking gain controls. I kind of got used to the bigger PowerLight controls, so the smaller knobs were just a “feel” thing. Overall, the PLX2 amps are worth upgrading to, if need just a bit more and feel you are on the edge on capability. But if you are not a QSC ampli- fier fanatic already, I suggest that you try these new amps. 
What it is: High Power Compact Power Amplifiers
Who it’s for: Professionals and Musicians who desire smaller, lighter amplifiers and are on a budget.
Pros: Clean Sounding, Very Efficient, and Flexible.
Cons: Variable gains per model.
How much: QSC PLX1804 $919.00 MSRP, QSC PLX3602 $1,549.00 MSRP
