Striking a balance between simplicity and control
by Craig Vecchione
Pro Audio power amplifiers don’t enjoy much glory. They’re expected to perform quietly and flawlessly night after night, often in less than ideal conditions and with little if any care or maintenance. We often take them for granted, but when they fail to work, we sure notice.
Perhaps to give them some more “glory”, there’s been a trend in recent years to add extensive features to power amps. Limiters, crossovers, high-pass filters, EQ and all manner of digital controls for these features seem to being showing up on more and more amplifiers. Of course there’s a price for all these features, and not everyone needs them. The QSC GX5 strikes a more modest balance of simplicity and control in its feature set, opting to offer a well-protected amp with only a single crossover and the channel attenuators as user-controlled features. The power output is suited for many popular club-level speakers.
What You Need to Know
● Reasonable power—8 ohms/1kHz (both channels driven) 500 W, 4 ohms/1kHz (both channels driven) 700 W
● Input sensitivity of 1.2 Vrms with voltage gain (8 ohms) up to 34.4dB
● Output circuitry: 2-tier Class H
● Input Connectors: balanced paralleled 3-pin XLR and 1/4" TRS, unbalanced phono
● Output Connectors: Speakon®, 1/4", Binding Posts
● Considerable amplifier and load protection: short circuit, open circuit, thermal, RF protection load protected against DC faults
● Front panel controls and indicators: Gain controls with 21detents; red clip LEDs; proportional, 0.1\% THD threshold green signal LEDs; threshold -35dB blue power LED, AC on
● Rear Panel Controls: full range/crossover switch for 100Hz, 3rd order lowpass filter for sub, 2nd order highpass filter (top)
● GuardRail™ protection reduces gain during overheating or clipping—enough to protect the amplifier circuitry without introducing excessive distortion or shutting down the amplifier.
● The GX5 isn't intended to drive 2-ohm loads and has no bridged output capability. For some users a lack of bridged output might be a liability, but without it there’s much less chance of damaging speakers with the resulting huge power outputs.
● In use the cooling fan was somewhat louder than with other amplifiers I’ve used. However this sample had suffered some shipping damage (more on that in a moment) and the noise could be a result of this.
● At 26 pounds the GX5 isn’t really a “lightweight” by today’s standards, where sub-15 lb. amps with twice the output are becoming commonplace.
For anyone who simply needs a power amp without all the “bells and whistles,” the GX5 really is a good choice. Most musicians simply need an amp that won’t quit, and QSC has a reputation for building very reliable amplifiers. As testament to this, my sample arrived at the door complete with rather extensive shipping damage. I didn’t intend to “drop test” this amp, but the shipper took care of that option. A corner of the box was crushed, and one of the front rack ears was bent. I feared the worst, but the amp worked just fine other than the aforementioned noisy fan, which may or may not have been the result of such rough handling.
Is there a market for a power amp that doesn’t “do everything”? I think so. With a street price around $400, the GX5 will power just about any speakers commonly used for the average club gig, and the internal crossover allows it to be used for a very simple biamped system with no other processing gear. With a 6 year warranty and QSC’s excellent customer service, the GX5 offers value not found in many other power amps.
Musician’s Friend QSC GX5 page (MSRP $499, “street” $399)
QSC Audio GX5 Page
Craig Vecchione is an IT professional by day, and dabbles in pro audio and bass guitar in his spare time. He’s been the moderator of the Live Sound Forum since 2006.