QSC Audio PLX2 - Manual

35
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# 1
By Mark Amundson
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 new
c 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
10.1 inches 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
h i g h - a m p l i f i e r
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.
QSC PLX2 Audio Power Amplifiers
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
Road Tests
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