Classe’ CT-M600 Monoblock Amplifier Reviewed
Gone 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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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.
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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I started off my listening session with AC/DC’s High Voltage (Atlantic/WEA) from the opening track “It’s a Long way to the Top (If You Wanna Rock ‘N’ Roll). The Classe’s gave me all the energy I could ever need to even the most extreme volumes. The guitars jumped from my speakers as I was playing them pretty loud but the power of the bass drum kept up and went to depths not often heard. The horns stayed in your face with plenty of air. “Rock ‘n’ Roll Singer” kept my room rockin’ with the powerful guitars and vocals while again the bottom end punched me in the chest like only hugely powerful amplifiers can do – yet the Classe’s never got edgy or annoying and no matter how high I pushed the volume the bottom end stayed controlled. “The Jack” only further demonstrated how well the power of these amps handled bass.
I spun up Al DiMeola’s The Infinite Desire (Telarc) as it is great music and recorded extremely well. From the washing machine sounds at the start of the title track, the sound was open and true to life and the knocking on the sides of the tub was powerful, but when the bass really kicked in the power and depth were simply amazing. Even more amazing was how well the delicacy of the guitar was kept totally separate from the deep bass lines. “Valentina” was excellent and the music seemed to simply flow from the system. Never did I feel I pushed these amps to work up a sweat much less run out of power. The opening of “Invention of the Monsters” is fast and complicated and the Classe’s handled the song with ease and control, with a musicality that was wonderful. “Race With Devil on Turkish Highway” is an unusual tune and covers the gamut from fast guitar to deep bass groves and the Classe’s didn’t miss a beat.
The Alan Parson’s Project I Robot (Arista) is a classic album well known to all rock music fans and from the start of the title track the space and dynamics reproduced by these amps were incredible. The music simply filled the room and had exceptional separation at all listening levels. I am always amazed at how much more depth bass has from powerful amplifiers even at low listening levels and the Classe’s reinforced that to me in spades. On “Some Other Time” the subtler qualities of these amps were allowed to shine. Space was huge and every note was discretely and accurately portrayed with authority and a musicality that just flowed from the speakers.
No mater what I played, even the Dead Kennedys, I never ran out of power and the bass lines stayed controlled even to extreme volumes. Jello’s voice on “Holiday in Cambodia” had all the edge and anger I remember, while the rash guitar lines kept pace. While I am in no way expecting you to use the Dead Kennedys for reference material, I loved how the limitless power of these amps brought power and life to this music. I listened through to “We’ve Got a Bigger Problem Now,” Jello Biafa’s rebuke to Ronald Reagan taking office. Listening to this track made me wonder what he’d think of our current political situation as I got lost in the angst and emotion of this old classic punk tune.
I moved to some old time blues with Junior Wells’ Come On In This House (Telarc) and the richness of Junior’s vocals and smoothness of guitar were amazing on “She Wants to Sell My Monkey” while the bass lines had the incredible depth I had come to expect from these amplifiers. The guitars notes jumped from the strings, I mean speakers, during the livelier passages and the dueling guitars were clearly distinct from each other. The train sound of the guitars on “Mystery Train” had clarity and power. On “King Fish Blues” the harmonica was lively while the slower nature of the tune came across with an ease that was wonderful. Junior Well’s voice was as good as I remember live acoustic.
No matter what I played through the Classe’s, from music to TV to Blu-Ray, they never let me down. I even went so far as to watch several scenes from James Cameron’s “Avatar” (20th Century Fox) in stereo fed by my Oppo NuForce edition Blu-Ray player and the spacious nature of the soundtrack was done incredibly well in two channel. I was impressed by how well the constant bass track of the film was handled by my main speakers using these amps, producing subwoofer-like levels and deep bass from my albeit large monitors.
The Classe’ CT-M600 monoblock amplifiers are damn near perfect and are one of the best amplifiers currently made, but for those who need massive weight to impress themselves or their friends, these amps won’t suffice. Aesthetics are always subjective, and while I think they look cool, your tastes may vary. I would be perfectly happy to have them sitting on my floor or on an amp stand let alone in a rack.
The power protection circuitry may require you to depress the front power button from time to time, depending on your power. Mine in Florida is terrible, especially in the summer when I had these amplifiers, and during the few months with these amplifiers, on three occasions I did have them enter protection mode and had to re-start them. This wasn’t an issue for me as they were on the floor in my listening room. Were they in a remote site, it would require more effort.
Classe’ has done the seemingly impossible with the CT-M600’s. They have made an amplifier that is capable of satisfying the most discerning audiophile yet allows for placement into a conventional rack with ease and minimal thermal management issues. Forget the ability to place them into your closet without worrying about heat, these amps sound simply amazing and are among the finest amplifiers I have heard. They offer bass control that can only come from the almost limitless power they offer yet they have an ability to handle subtle details equally as well, even to extreme volumes, and reproduce music with smoothness and ease.
Classe’s technology of active thermal management assures that however you install these amplifiers you will be rewarded with top performance, as it allows the amplifiers to get to optimum operating temperature quickly (in under 12 minutes) and keeps them there no matter how hard you drive them. Many other amps I’ve owned of lesser power run far hotter, and would simply not tolerate being in the closed in environment of a typical rack-based system. Classe’ tells me that in their own torture testing in clipping levels for hours, the fans never went above 30 percent use and after spending several months with these massive beasts I can see why. Even in my test, after hours on end at extreme volumes they never got more than warm and the fans were nearly silent and certainly never interfered with the sound.
The new Classe’ CT-M600 creates an entirely new category of amplifiers by successfully satisfying both the installers and audiophiles alike. If you are in the market for top tier performing amplifiers, these are the ones to audition, and while I know the $13,000 per pair price isn’t cheap, they can hang with amps costing much more. If you plan to build a home theater where your gear is stashed away in a closet or media room and want the best sound, these amplifiers are the only choice for true audiophile performance in such an environment and will reward you with some of the finest and most abundant power available.
• Read more about Classe and its products.
• Find more amplifier reviews from HomeTheaterReview.com’s staff.