QSC RMX 4050HD Power Amplifier

by Tom Young, 07.01.2003

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QSC, a company that needs no introduction in the power amplifier market, has added the 4050HD as its newest addition to the RMX series of amplifiers. The 4050HD is perfect for applications requiring big performance in sound reinforcement at a good value. With a $1,779 retail list price and the ability to deliver an impressive 4,000 watts of power, it should find a niche in a variety of live sound systems.

Features

The QSC RMX 4050 "HD" (Heavy Duty) design has more than twice the power of the earlier model RMX 1850HD and 60 percent more power than the RMX 2450.

The obvious difference upon inspection is that it is housed in a 50 percent bigger 3RU chassis, 16 inches deep and has a weight of 68 pounds. Per channel (two channels) power at 8 ohms, 1 kHz, 0.1 percent THD, the RMX 4050HD is rated at 850 W, 1,400 W at 4 ohms and 2,000 W at 2 ohms. In bridged mono at 8 ohms it has a rating of 2,800 W and at 4 ohms a substantial 4,000 W.

The front of the amplifier has a power on/off switch, channel gain controls, signal presence and clip LED indicators. Cooling is improved with this model providing more than twice the cooling power without any increased noise. It is handled by the venting on the front panel and a continuously variable speed fan with rear to front airflow. Like all RMX series amps, the back panel features balanced 1/4-inch TRS, XLR and barrier strip inputs. Outputs can be terminated with Neutrik Speakon or binding post connections.

Each channel has its own full-size toroidal power transformer, and the output circuit advances from two-tier Class H to three-tier Class H

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. This unique dual mono, high current power supply can deliver double the power, less AC current is wasted, and directs the power more accurately to the output section. DIP-switches are provided on the rear panel for 30Hz or 50Hz filtering and protection settings. The RMX 4050HD amplifier comes with QSC's three-year warranty.

In Use

The first thing I noticed upon unpacking the amp was its weight of 68 pounds - considerable, as today most amps are getting lighter. However, when listening later on, the brute power matches its physical substance. Using the Neutrik Speakon connectors, I terminated the amp in stereo operation to two Turbosound Floodlight TSW-721 21-inch subs per side running the amp at 4 ohms and played The Eagles Live CD through the PA. The subs are rated at 1,200 W and responded extremely well with smooth transients at 1,400 W per channel.

Later in the day I was able to listen with the band, which included drums, bass, guitar and piano. The bass from the subs was tight and clear and sounded very pleasant to the ear. There seemed to be plenty of headroom in the sub bass area that was powered by the RMX 4050HD. I was pleased to hear minimal fan noise from an amplifier of its size.

Its regular 15A plug is a real advantage. Most amps of this power use a higher current plug that can't be inserted into a standard Edison outlet.

Summary

The QSC RMX 4050HD is an excellent addition to the RMX line. For less than 50 cents per watt, this amplifier provides tremendous value and performance. For anyone looking for solid power without breaking the bank, it delivers as promised.

Review Setup

Yamaha PM4000 console; Turbosound Floodlight TSW-721 subs; BSS OmniDrive speaker processor.

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