Classe Sigma AMP5 Five-Channel Digital Amplifier Reviewed

Classe-Sigma-AMP5-thumb.jpgClasse is one of those AV brands that many AV enthusiasts lust after. A gorgeous industrial design, innovative technology, forward-thinking features, and overall great sound have made the brand a killer for decades. Today, you can add value to the long list of Classe accolades, thanks to the recent rollout of the brand’s Sigma Series–which includes a two-channel amp (the AMP2, $3,500), a five-channel amp (the AMP-5 reviewed here, $5,000), and a smoking-good little AV preamp also priced at $5,000. Basically, for the price of a Classe SSP-800 reference AV preamp, you can assemble a full 5.1 theater package. That’s a value proposition that many will have to consider strongly when the next urge to upgrade hits, as this is a meaningful upgrade over anything that even the best, most pricey AV receivers can provide.

Having owned (and loved) the Classe SSP-800 and a pair of Classe’s CT600 powerhouse mono-block amplifiers, perhaps I come into this review a bit jaded. The Classe SSP-800 is one of the finest AV preamps on the market today and has stood the test of time in an ever-changing home theater market. The CT600 is one of the finest amps I have ever opened a Word file to gush over. It has more power than one would reasonably need, with the accuracy of uber-high-end amps costing tens of thousands of dollars. I would have never sold my reference Classe setup but for the fact that I moved from my home and knew that I would be without a large-format AV system for at least 18 months. Roll the tape forward to today, and the time came to start putting together a new system. Dolby Atmos, DTS:X, Crestron-this-that-and-the-other-thing, power-over-IP, enterprise-class Internet switching and routing, lighting control, DVRs, pool and irrigation controllers–all packed into my two larger Middle Atlantic equipment racks. When it came time to look into some new AV electronics, cutting-edge technology was one draw, but so was smaller, more rack-friendly gear. Enter Classe’s Sigma products, including the AMP5.

Priced at $5,000, the Classe AMP5 reminds me a lot of my trusty old Proceed AMP5 from nearly 20 years ago. The Classé is a modern version of that under-rated workhorse amp. It’s a 200-watt-per-channel (times five), two-rack-space Class D amp that can respectfully drive nearly any and every type of speaker. Because I needed more channels of power, I also added a Classe Sigma AMP2 ($3,500).

I know what you are thinking: Class D amps sound clinical and lifeless. They have no real bass and are more for utility than audiophile applications. Years ago, I might have agreed with those clichés, but not today. There are a whole host of Class D amps out there that sound simply fantastic, and I say this as someone who has recently owned big Class AB amps and even a 30-watt Class A amp.

Classe-Sigma-AMP5-rear.jpgThe Hookup
Installation was a snap, as the Classe Sigma AMP5 can be easily fitted for rack mounting. If you are not rack mounting it, you are still in for a cakewalk of an installation, as this Class D amp runs cool to the touch–thus no need for special accommodations for heat, as is the case with nearly every other multichannel power amp. And for weight, the entire amp weighs 23 pounds out of the box. Amazing.

I mated the Classe Sigma AMP5 with the Classe Sigma AV preamp (without the EQ engaged). My speaker system featured Focal Diablo Utopia speakers up front and Sonance eight-inch in-ceiling speakers in the surround positions, with an SVS SB-13 subwoofer.


Click over to Page Two for Performance, The Downside, Comparison & Competition, and Conclusion…


Out of the box, the best way I can describe the AMP5 with music is to suggest that it doesn’t sound like a Class D amp; it has much more of the tonality of a traditional Class AB amp. On “Postales” from Ferderico Aubele’s Grand Hotel Buenos Aires album, I heard very controlled bass that set up the excellent imaging. This Latin-loungy track features a smooth Spanish guitar solo that was round-sounding yet still vibrant. There was lots of space between the main elements of the track, as well as the accordion fills.

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On “Waiting for the Sun” by The Doors, I heard a good contrast between Robby Krieger’s whiny guitar rifts and powerful chord progressions. The melodies dancing on top of the track never lost their vibrancy when the AMP5 was engaged, but there was no lack of power in the low-register chords. Jim Morrison’s vocals sounded commanding and in front of the mix, as they should be. Overall, the balance on this often complex-to-reproduce song was notable.

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“Turn It on Again” by Genesis from the under-rated Duke album is another complex rock track with great dynamics and a good layering of details. At high volume, I could hear Phil Collins’ nifty drum fills clearly, while his voice was poised and present. There was little to no fatigue in the high frequencies, as you sometimes hear with Class D amps. What was even more notable was the lack of that “cold” sound associated with Class D power amps. It was really easy to forget that I was listening to a digital amp, even at very high volume levels.

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I reached into my stash of DVD-Audio, SACD and other HD discs, and I pulled out the Audioslave 20-bit Dual Disc (remember that short-lived format). I spun “Show Me How to Live” in my Oppo BDP-103 Blu-ray player that thankfully can pretty much play any disc you desire. Chris Cornell’s voice is among the best of his generation, and this rock-solid track highlights his talents fantastically well. Where the test comes is at the first chorus, where cymbals are blaring, bass guitars are rocking, and there’s an overall explosion of the dynamic window. Despite being rated at a mere 200 watts per channel, the Classe AMP5 laughed at the challenge of this bombastic track. Control, poise, and presence were the notes I scribed through my listening session. While I am used to bigger Classe amps in the CT600 mono blocks, I couldn’t get to the end of the 200 watts here in the AMP5 when driving my easy-to-power Focal Diablo Utopias. Consider the difference in price between the reference mono blocks for two channels and the AMP5 at five channels, and you’ll start to see the overall value of the AMP5.

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Moving to movies, I became drawn to the Classe AMP5’s ability to go from subtle details to more dynamic or complex material with ease. In the opening of American Hustle (Blu-ray) during the “comb-over scene,” where the viewer witnesses the installation of the worst 1970s toupee ever worn by a human being, you can hear all of the micro-details of the glue being applied and all of the other awkward preparation rituals. The scene just makes you want to wince until the opening credits roll and America’s “Horse With No Name” comes into play, and you hear just how musical the AMP5 can be. The amp has the ability to go from super-detailed to bombastic to musical at the flip of a switch (pun intended).

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With Skyfall, one of the more recent James Bond films with Daniel Craig, the Macallan scene is one of classic Bond kitsch. Our hero is asked to shoot a shot of 1962 Macallan scotch resting on the top of a woman’s head…or else. He misses everything with his shot, but the shot itself–from a vintage gun–rings out with tremendous dynamics in an empty public square. You can hear the blast of the gun at first, then the crumbling of the rock behind her. More shots are fired, and hijinks ensue…followed by suitably twangy Bond guitar rifts and roaring helicopters to the rescue.

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Perhaps the best juxtaposition of details and dynamics I could find with the Classe AMP5 was in American Sniper (Blu-ray)–a shooting scene in which a mother and son walk into an open-air street, and it seems as if the young child has an RPG. Bradley Cooper, as Chris Kyle, has to make an incredibly hard decision to shoot or not. While he makes the right decision, you can hear the bullet nearly cut through the air. You can hear the low-frequency rumble of the tank’s tracks as the U.S. troops support the day’s effort. Call for prayers ring out in the distance on dingy, horn speakers and sound both eerie and authentic. American Sniper has plenty of booms and bangs to test your system, but the emotional drama paired with the subtle resolution of fine audio details, thanks to the AMP5, makes for one hell of a movie demo.

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The Downside
There is a lot to like about the Classe AMP5. It runs cool. It lacks the cliché sound of a Class D amp. It is small and fits in a rack nicely. If you wanted to pick on the fit and finish of the amp, I guess you could go there. It only comes in a matte black. Higher-end Classe products come with an Apple-like white finish that is nothing short of jaw-dropping.

For some systems, 200 watts of power might be too little. For me, my speakers just don’t need more than that, even at the high levels at which I tend to test my system.

One might point out that other taller amps find a way to stuff seven channels of amplification into one chassis (think: ATI, Anthem, Lexicon), yet this 30-pound amp only gets five channels under the hood. With Atmos, DTS:X, and other formats coming, you are likely going to need more than one amp to power your entire system if you want the best surround sound that money can buy. Luckily, that’s why Classe makes the two-channel version of the amp and will gladly sell you a second five-channel amp if needed.

Comparison and Competition
Because the Classe AMP5 sounds unlike most Class D multichannel amps, there are plenty of amps one could compare it to. Most notably for me would be ATI’s 6007, which is a modular amp (from two to seven channels) that I reviewed as stereo amp. It’s bigger and more powerful. It’s a Morris Kessler design, and it sounds great. It also is heavy, ugly, and big compared with the Classe. At seven channels, the ATI prices out at a little over $9,000.

Krell’s Chorus 5200 is a 200-watt-per-channel five-channel amp that uses Krell’s new iBias technology that has received rave reviews. The industrial design of the Krell is very nice, and the advancements in the Krell sound, albeit from a different design concept, is worthy of consideration. The Chorus is $7,500.

Rotel makes a wonderful digital amp, as does NAD. Red Dragon Audio’s M500 MKII 500-watt-per-channel mono amps can be used to make a really powerful statement at about $1,000 per channel, although they aren’t really a one-chassis multichannel amp solution. They do have the audiophile chops to compete with the above-referenced products. Outlaw Audio’s 7700 is another less-expensive option at $2,149 for a seven-channel, one-chassis power amp.

Finally, a Class D amp that doesn’t sound digital. The Classe AMP5 is a balanced, capable, and useful amplifier that is just as comfortable playing John Coltrane as it is playing John Mayer. It’s an amp that can resolve the smallest audio cues yet, in an instant, roar into the most dynamic action your Blu-ray player and AV preamp can feed it. Make no mistake: no AV receiver at any cost can compete with a combination of a Classe Sigma AV preamp and an AMP5 on so many levels.

Additional Resources
• Check out our Multichannel Amplifier category page to read similar reviews.
New Sigma Preamp and Amps From Classe at
• Visit the Classe website for more product information.