50 years ago The Beatles performed at Shea Stadium to a crowd response so enthusiastic that you couldn't hear the band. From the moment that Ed Sullivan introduced the band, rock music history was changed forever. It was August 15, 1965 and Beatlemania had definitely infected the US rock audience, spawning the famous scenes of them running away from crowds of screaming girls.
While the cultural impact of the Fab Four would echo for decades, so too would these massive boisterous audiences change the business of sound reinforcement. The obvious problem was how to amplify the music enough to keep up with the ever-increasing audiences that crammed into concert halls, stadiums and outdoor festivals. Sound systems needed a lot more speakers to reproduce the music cleanly and audibly to larger and louder crowds, and this meant more power amplifiers. In those days power amplifiers were relatively low power to today’s amplifiers, they were heavy, and took up a massive amount of space. Fortunately concerts were a lucrative business and produced more than enough revenue to pay for these huge systems to be moved, set up and hauled across the country. But as the decades rolled by, touring and fuel costs continued to rise. The new challenge became how to make power amplifiers smaller, lighter and cooler, since all those amps also produced a ton of heat.
Fortunately, in the time since that Shea Stadium show and The Beatles' famously inaudible appearance, audio designers have developed better solid-state power amplifier technologies. These new designs yield a lot more power, run cooler and weigh considerably less, opening the door to amplifiers like the Carvin Audio DCM3800L, which offers up to 1800 watts per channel yet weighs only 15lbs. Finally everyday musicians have access to high-powered amps that are light enough to fill a rack without needing a team of roadies to move it.
For the last 30 years, most power amplifiers had two channels, intended to reproduce a stereo mix conveniently. But if you wanted to add a couple of channels you still had to get two of them, doubling the space required. Along came the four channel power amp, like Carvin Audio's DCM2004L, providing a solution for more than two channels in the same space and weight of a two channel amplifier.
But Why Would I Need Four Channels in a System Like Mine?
"Okay, I understand a 4-channel amp provides more channels in less space, but why would I need four channels?” Adding a 4 channel power amp to a modular sound system increases its versatility so you can optimize your system for changing venues and band member needs. All-in-one PA mixers can be a convenient solution, if it has the features you need, but they often lack flexibility for your growing professional needs. Carvin Audio's C1648P 16-channel, 4 amp powered mixer is an exception, offering the best of both worlds by giving you an amp routing selector and both full mixer outputs and power amp inserts. A modular system with one or even two stereo amplifiers will get larger when you need to have another monitor mix or want to add subs to the mains. A 4-channel amplifier increases your options without adding more physical amps.
Creativity is Your Only Limit
With a single four channel power amplifier one of the most common configurations is to use two channels for your main speakers and two channels for your monitors. This setup provides stereo mains and two monitor mixes (in case the drummer doesn't want the lead singer twice as loud as the bass in their monitor). But you don't have to limit yourself to tradition. Perhaps one channel provides more than enough power in your application to run both main speakers, and you really need three monitor mixes. Maybe you really only need one monitor amp channel with several monitors on it, and you need two amp channels for subwoofers that take a lot more power. It makes sense to use two channels to power the subs, one channel for a pair of full-range main cabinets wired in parallel, and the last channel for your monitor mix. As long as your speakers are receiving enough power to suit your needs, you are free to dedicate each channel to any signal source you need to amplify. And the output load impedance on each channel does not need to match any of the other amp channels, providing you are not going below the minimum operating impedance of each channel.
Once you free your mind to route your amp channels into a variety of configurations, you will find it becomes a lot easier to adjust to unexpected situations on the job, or to mix and match components to create more custom sound systems. Extra channels are often needed for installations where you have different speaker arrays covering large areas, asymmetrical areas or many individual zones. Carvin Audio's DCM2004Lx 4-channel power amp has onboard digital processing to let you adjust EQ, gain, and limiting for each amp channel in these applications. In the recording studio a 4-channel amp can be a compact solution to power two sets of reference monitors in stereo for easier input signal switching between different types of monitors or for powering control room and the performers’ room monitors.
The next time you find yourself one monitor mix short or needing a third main to cover a smaller side audience area, remember a 4-channel amp will keep the rig the same size while adding more flexibility. Try listing off each audio signal you need amplified and then inventory your available mixer outputs and power amp channels with an eye towards creative problem-solving. Before long you'll approach system changes on-the-fly with a new mindset that offers a lot more flexibility. What would you amplify with an additional two power amp channels? Let us know in the comments.