While it seems like switch-mode power amplifiers get most of the press nowadays, there has been a trickle of new conventional amps to enter the marketplace. Among the most popular, is the RMX series from QSC. While it’s true that these amps are a staple in popular MI chain stores, some of them, like the 5050 ($2,549) that I was dispatched to review, have power ratings that would qualify them for professional applications.
Product PointsApplications: Live sound, installation
Key Features: Two-channel; high-pass filters; limiters; 1,600W per channel @ 4 ohms
Contact: QSC Audio at 714-754-6175, Web Site.
For those who are familiar with QSC switch-mode amps like the Powerlight and PLX, the controls and chassis design of the RMX will look very familiar. The RMX has loads of front panel ventilation slots along with a power switch, gain controls and LEDs that display signal present and clipping. The rear panel of the RMX has an input bank (barrier strip, XLR and 1/4-inch TRS) and speaker connections on Speakon and binding post. The amp also features QSC’s mode switch bank of DIP switches. For those unfamiliar with this feature, it allows the user to operate the amp in stereo, parallel or bridge mono mode. In addition, you can apply high-pass filters (30 Hz or 50 Hz at 12dB per octave) and clip limiters. Hinting at the amp’s power capacity, it is equipped with two internal 20-amp breakers (one for each channel) and a NEMA 5-20 plug on the AC cable.
Perhaps you have seen QSC’s advertisements for the RMX5050. It depicts a Great Dane towering over a nervous Chihuahua with the byline “Move over little dog, the big dog’s movin’ in.” The metaphor here is that the 5050 has enough power to be of gigantic proportions. Well, with output power ratings of 1,600W per channel @ 4 ohms and 2,000W per channel @ 2 ohms (20 Hz – 20 kHz, 0.1% THD both channels driven) it would seem a very “big dog” indeed. Other specs include a damping factor of >250 (8 ohm load) and input sensitivity of 1.42Vrms. All of this power is mounted in a 3RU chassis that weighs in at a bruising 75 pounds.
The RMX5050 is an absolute beast when it comes to weight. I would advise making sure that you have very stout rack rails (front and rear) if you plan to transport this amp. Also, even though the RMX is designed to be efficient for its Class H topography, it is still an AC hog (13.9 amps typical with a 4 ohm load). Some of the venues I work in have limited power and I am often forced to run a whole PA on 20 amps — something very doable with switch-mode amps. So in the interest of security, I made sure to only use the 5050 in those venues where a dedicated circuit was available for the amp.
Once the amp was turned on, it was all wine and roses (or chew toys and Milk Bones). As billed, the RMX5050 has gobs of power and it handled subwoofer duty (8 ohm and 4 ohm) with flying colors. Even with the added stress of a subharmonic synthesizer applying additional low-frequency content, the amp had plenty of “bark” for chest pounding kick drum and organ tickling bass guitar. This may be psychological, but I found myself liking the sound of the 5050’s response as compared to my switch-mode amps. Maybe it’s the knowledge that the electric meter was spinning a little faster that influenced me — just like stomping on the accelerator of a big V8 car has a thrill that is unrivaled, even by faster turbocharged, high-revving four cylinder engines.
If you need big power, an affordable price ($2,549 though it streets for around $1,499) and you aren’t that concerned with weight or power consumption, then the RMX5050 is the amp for you. With such ample power and a modest price tag, it would be ideal for installs in clubs or worship houses and even certain touring situations.