QSC Audio has established itself as a leading manufacturer ofamplifiers for live sound reinforcement. In conjunction withbreakthroughs in amplifier technology, such as its patented PowerWaveswitching power supply, which drastically reduces the weight ofhigh-powered amplifiers, QSC also developed QSControl, a networkingtechnology for remote amplifier management, and RAVE (Routing Audio ViaEthernet) digital audio networking.
Most recently, QSC turned its attention toward developing a line ofhigh-powered amplifiers for critical use in studio and home theaterapplications. The result is the new Studio Reference Amplifier seriesthat comprises three models: the SRA1222, the SRA2422 (reviewed here)and the SRA3622. Power outputs are rated at 200, 425 and 725 watts perchannel, respectively (both channels driven into 8 ohms across theaudio band @ 0.03% THD). For those who require more power, all SRA ampsmay be bridged for mono operation, resulting in a threefold increaseover the rated stereo output.
SOLID, VERSATILE DESIGN
SRA amplifiers were designed with a variety of installationscenarios in mind. Rear panel DIP switches are provided (per channel)to configure the amps for stereo, parallel or bridged mono operation,and to turn the low-frequency filter on/off, select 20Hz or 50Hzroll-off and turn the clip limiter on/off. According to thewell-written user’s manual, the limiter kicks in only when clippingoccurs, quickly reducing gain to remove the possibility of damage tothe speakers. Rear panel input uses locking XLRs (pin 2 hot) and RCAconnectors — unusual for a QSC amp, but this facilitates use inhome theater applications. Speaker output is available on Speakonconnectors and touch-proof binding posts that accept bare wire, spadelugs and dual-banana plugs. To facilitate bi-amplification, output fromchannel 2 is available on pin 2+/2- of channel 1’s Speakon jack. Withamps as powerful as these, it’s comforting to see that all of theoutputs are safe from prodding fingers.
The only obvious control on the SRA2422’s beautiful aluminum frontpanel is an on/off switch. A small security cover hides the gaincontrols, enabling the gain pots to be locked out from unwantedtweakers. The gain controls will come in handy for anyone using smallmonitors or in need of adjusting speaker levels in a multichannelsystem. QSC includes rack ears, a hex wrench to remove the securitycover and a 12-volt cable for use with the remote turn-on function.
IN THE STUDIO
I put the SRA2422 to work in my studio with a Yamaha 02R Version 2,Westlake Lc8.0 monitors and Monster Cable Z3 reference cables. (TheSRA2422 took the place of a Bryston 3B amp.) Initially, I was concernedwith the fact that the SRA2422 uses a fan for cooling, but in practice,the fan never became audible because it’s a variable-speed unitproducing only the amount of airflow necessary to keep the amplifiercool.
It takes about eight seconds for the SRA2422 to go through thesoft-start sequence — a welcome feature for anyone who has blowna circuit breaker while turning on a high-powered amp. When switchedon, the green power indicator illuminates dimly and then brightly whilethe red clip LEDs light. When the SRA2422 is ready, the red LEDsextinguish. Audio is muted until the amp has stabilized, so you’ll hearno pops or thumps during power up. The SRA2422’s green signal LEDsindicate the presence of audio.
With no input connected, the SRA2422 was virtually dead quiet. Withmy ear next to one of the Westlake monitor’s tweeter, I could barelyhear the slightest hiss and absolutely no hum, so it was easilyestablished that the SRA2422 has a very low noise floor. Even with the02R connected and its volume cranked up, there was still virtually nonoise. In addition to the SRA2422’s high S/N ratio, its other obviousstrength is the seemingly limitless power reserves. When playing hardrock or dance tracks at volumes that were way too loud to becomfortable for extended listening, the SRA2422 cruised along withoutan audible gasp or a flicker of the clip LEDs. In fact, I never saw theclip LEDs illuminate. With this kind of reserve, the SRA2422 will haveno trouble running mid-field or large main-type monitors cleanly tohigh listening levels. Both the high- and low-frequency extremes wereuncolored and extended, though I preferred running the amp with thelow-frequency filter bypassed. In the 50Hz position, kick drums andsynth bass were thinned a bit, while in the 20Hz position, thedifference was barely noticeable. No doubt the filter will be usefulfor powering monitors with limited low-frequency capabilities, such asthe Yamaha NS10M or the Tannoy Reveal.
The QSC SRA2422 does what a reference power amplifier is supposed todo: make the audio signal louder and get out of the way. Along with itstechnical strengths, the SRA2422 looks good and stays cool withoutintrusive fan noise. Combined with its low noise floor and ample powerreserves, the SRA2422 should be on the audition list for anyonerequiring a top-notch power amplifier.
QSC Audio, 714/754-6175, www.qsc audio.com.
Steve LaCerra, a veteran pro audio journalist, is based out ofNew York City.