Classe' CT-M600 Monoblock Amplifier Reviewed

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Classe-CT-M600-MonoAmp-Reviewed.gifGone are the days of massive amplifiers and speakers in a dedicated listening room. Today's designers need to conserve floor space and until now, putting true high-end, high-power amplifiers into a rack-mounted system simply didn't work. Heat and size were two of the biggest issues and 600-Watt mono-blocks produce tons of heat - or do they?

Most high-end home theaters in the U.S. have the components hidden away in closets or small media rooms to make the theaters cleaner and more modern. While making the theater space more open, the small spaces that now house components to control the entire home have their own problems, and one of the biggest is dealing with all the heat those components generate. The definition of heat depends on whom you ask; in physics, it is a process of energy transfer between bodies due to thermal contact, and this transfer can occur through conduction, convection or radiation. Enough of the physics. All things doing anything generate, and must get rid of the heat they produce in order to maintain a steady temperature. Conventional heat sinks ventilate passively and can be very ineffective in a high temperature environment. What is the true audiophile to do when it comes time to go home theater?

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• Read more about Classe and its products.
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Classe' is one of the world leaders in high-end audio and AV system components and has created an entirely new line of gear designed for the install market, but which will also satisfy the discerning audiophile. The new CT series of components is designed to be rack mounted while maximizing performance and minimizing the problem of thermal management. The subjects of this review are the top of the line Classe' CT-M600 amplifiers that boast 600 Watts per channel for a retail price of $6,500 apiece.
The new series of Classe' CT products is specifically designed towards the needs of the modern U.S. home theater market, where people want great sound but don't want those coffin sized amplifiers sitting on the floor between their speakers. In order to make such super powered amplifiers able to be rack mountable without overheating themselves and the other gear in the rack, Classe' did some serious engineering work. First they revamped the conventional heat sink and added active thermal regulation, which allowed them to place a multitude of heat sinks closer together, increasing surface area in a smaller space, thus allowing for better heat dissipation. Then the addition of a computer-controlled fan further enabled them to ensure the amp quickly reaches its optimal temperature and doesn't stray from this no matter how hard it is run. They even went so far as to add air filtration so that particulate matter in the room or cabinet won't be drawn through the cooling fins of the amplifiers to hamper the process.

I am sure I have already worried the die-hard audiophiles with this information, but hold tight: the new Classe' amplifiers not only maintain perfect, let me repeat that - PERFECT operating temperature no matter how hard they are run, then by doing so they also significantly increase the life expectancy of the amps themselves, and due to minimizing heat to the surrounding components, they potentially extend the life of your other components as well. Let's face it, the ability to rack mount 600 Watt per channel mono-blocks simply hasn't existed until these came out. Sure, you could put other manufacturers' monaural amplifiers into your rack, but it would take huge fans to control the temperature of the rack and will be extremely difficult to optimize thermal management. Classe' has done all this for you and also created one of the coolest running amplifiers that rivals the heat management of digital amps while keeping the many benefits of class A/B operation.

The Classe' monoblocks also offer tons of protection for themselves and your speakers from output overload, DC offset, excessive operating temperature and mains voltage outside of acceptable range. Should any of these events occur, the amplifiers would immediately switch into standby, protecting your system from catastrophe. I live in Florida and during my months with these amplifiers, some power issues did send them into protection mode. The amps were easily returned to running state by tapping and holding the front power button and never did I have any ill effects from this. While protection is a great thing, it can be a slight nuisance for those who have them securely tucked away as in a closet or remote site.

The CT-M600's are full sized components at 17 inches wide (19 with the faceplate on) by 18 and a half inches deep and almost seven inches tall and weigh in at 89 pounds each. The faceplate that comes with them is wider so when they are rack mounted it will cover all the hardware for the mount making for a super clean look, and the CT-M600's come with everything needed to rack mount or to use them as freestanding units. Normally the faceplate clips in so as to allow access to the air filter employed in the active thermal management, but for free standing use they include hardware that allows fixation of the face plate in case someone tries to pick the amplifier up by it.

The CT-M600's spec out at 600 Watts per channel into eight Ohms and 1,200 Watts into four Ohms with a frequency response of 1Hz to 80kHz at -3dB with less than 0.002 percent distortion via balance connections and just twice that for single ended, with a signal to noise ratio of -120dB at peak output into eight Ohms at 22kHz. These are numbers that are so far beyond the limit of human hearing they approach ridiculous, but do point to just how well this amplifier is designed.

The Hookup
My Classe' CT-M600 monoblocks came shipped on a medium sized pallet and to my amazement were delivered by a full 18 wheeler into my little subdivision. The driver was kind enough to drop them into my garage and leave the pallet with me. Unpacking them was relatively easy, except for the Florida summer heat I had to deal with. I cleared off the shrink-wrap and cut through the binding straps to free up the two white Classe' boxes. Both were held together on all four sides across the bottom of the package with heavy strapping tape, which, once cut free, allowed me to slide off the five sided top, giving me the first view of the amplifiers.

The bottom of the packaging is open so each side falls away allowing easy access to the amplifiers. All the necessary hardware for rack mounting or freestanding use is included, and for those who desire, upgraded feet are available. Unpacking these amplifiers was amazingly easy, due both to the breakaway design of the packaging and their relative light weight. Many other amplifiers in this power category weigh over a hundred pounds apiece, yet the Classe's were easily manageable by a single person at only 89 pounds. Were I rack mounting them, I'd have wanted another pair of hands, but I put them on the floor in between my main speakers. I didn't need to do more than screw on the optional feet and place them where I had room and attach the front fascia. Since these amplifiers are designed to manage heat in a rack-mount environment, I placed one directly on top of the other, with only the small feet between them, to see how they would perform.

I wired the Classe' CT-M600's into my main rig which has the EMM Labs TSD1/DAC2 CD/SACD player with the DAC2 also fed by an Apple Airport Express for streaming MP3 and mainly AIFF files from my music server into an Audio Research Reference 5 preamp for some time as well as directly to a Classe' SSP-800 AV preamp to my Escalante Fremont's for speakers. All cabling in the system was Transparent Reference XL balanced interconnects and speaker wire. I swapped the Classe's in for my Krell Evo 403 amplifier, and set about doing this review mainly for two channels, though I did use the pair for plenty of movie and TV watching, using my Krell to cover the center channel.

The front panel of the CT-M600's is pretty simple yet elegant. A smooth machined fascia runs from side to side in flat black, while a slimmer deep grey piece runs the same way across the middle of the face with a recessed middle section. On the sides the black piece slopes back smoothly and a single small bar across the middle of the bottom is the power button and indicates the units status. The rear sports dual speaker binding posts, both balanced and single ended inputs as well as a host of control options including Classe's CAN-Bus port for integrating these with other Classe' components as well as an RS-232 port, both IR and DC triggers, and USB port. A 15 Amp IEC connector finished off the rear. And there is no 'hard' power switch on this amplifier, just the front power button.

The amps I received were brand new, so once I made the swap between my amp and the Classe' monoblocks, I set out to run them for a few hundred hours to burn them in. Well, after six hours playing at levels that required me to be out of the room, OK, I was out of the room and wanted music so I thought I'd kill two birds with one stone and burn the amps in, test the heat management and listen to my main rig from a few rooms away. I was amazed to see the amps were barely warm to the touch. The fans were running but at such a level they were inaudible even during quiet passages, and the air being vented as barely warm. This was with both of them sitting directly on top of each other, playing at extremely high levels for hours. I let them run for weeks with various sources to fully burn them in and never found them to be more than warm.

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