Classé CT-M600 & CA-M600 monoblock power amplifiers Page 2

A large toroidal transformer behind the front panel supplies power to three stacked printed-circuit boards behind the transformer. The bottom two boards carry multiple storage capacitors, the top board the relay and housekeeping circuitry. All the audio circuitry, including the 36 output devices, is carried on two six-layer boards mounted either side of the fan tunnel. This allows signal paths to be very short, minimizing any parasitic effects and keeping the amplifier's noise floor very low. The circuit is new rather than developed from earlier Classé designs. Both balanced and unbalanced inputs are provided, but Classé warns that operation from the unbalanced RCA jack is not quite as immune from RF interference as from the balanced XLR. (If the RCA input is used, a jumper needs to be inserted between pins 1 and 3 of the XLR, to tie half of the balanced circuit to ground.) There are two pairs of shrouded speaker terminals to allow easy biwiring, and the amplifier offers a full array of trigger inputs and outputs, Classé's own CAN-Bus control protocol, and IR Remote repeaters, as well as USB and RS-232 ports.

Classé provided me with two sets of accessory feet ($140) to use with the CT-M600s, which use Navcom inserts to provide isolation from vibration.

Delta Force
Several months after I had received the CT-M600s, Classé sent me a pair of CA-M600s. This is the same amplifier, but packaged in Classé's traditional Delta-series enclosure, with its brushed-aluminum front panel curved round to form the side panels. The fan pulls in air from a square slot concealed on the black front-panel insert. I studied both models with their vibration-damped tops removed; under the skin, the two appeared identical, the only apparent difference being the orientation of the toroidal transformer: vertical in the CT-M600, on its side in the 100mm-taller CA-M600. The more domestically acceptable styling of the CA-M600 adds $1000 to the price of a brace of amps.

Sound Quality
I used first the CT-M600s, then the CA-M600s, for a total of nine months. In that time I used the amplifiers with a wide variety of loudspeakers, from the current-hungry Focal Maestro Utopia IIIs (reviewed in July 2010), the miniature and exquisite Harbeth P3ESRs (reviewed in August 2010), to the supersensitive, horn-loaded Acapella High Violoncello IIs (reviewed in September 2010) and the weird and wonderful Gradient Helsinki 1.5 dipoles (reviewed in November 2010). Following the return of the Gradients, I returned to the Harbeths to review some digital source components. In all that time, I never felt I had a handle on the sound of the Classé amplifiers.

And as I prepare to send this review off for copyediting, I still don't. In either of its guises, the 'M600 is the consummate chameleon.

Yes, I could draw comparisons with other high-performance amplifiers. The Parasound Halo JC 1 monoblock, for example, sounded more intense in the treble. But that doesn't mean the Classé sounded dull. Far from it. Yes, it had a firmer grip on the Focal's big woofers than did the Simaudio Moon Evolution W-7, but that doesn't mean it sounded lean. Far from it. Yes, I enthused about the transparency of the NAD M2 Direct Digital amplifier (reviewed in March 2010) fed straight digital data via S/PDIF. But that doesn't mean the 'M600s didn't sound transparent. Far from it. Yes, one reason I had bought the No.33Hes was the enormous soundstage they threw, but that doesn't mean the Classés' soundstage was any less expansive than my memory of the Levinsons'. Far from it.

Whatever speakers I used with the Classé monoblocks, each pair of speakers sounded more like themselves than they did with other good amplifiers. Whatever recordings I played through the 'M600s sounded more like themselves. With both speakers and recordings, it was if the colors in the sonic picture were more intensely saturated. The amplifiers' deathly quiet level of background noise allowed them to step out of the way of musical details that I have rarely experienced from electronics. Their enormous dynamic range allowed musical climaxes to be reproduced in full measure, even with modest speakers that you'd think would be overtaxed.

As I finish writing this review, the CA-M600s are driving the Harbeth P3ESRs. The front-end is the dCS Debussy processor taking USB data from my Mac mini running PureMusic with AudioQuest's new Coffee cable. There's no preamp in the system. I'm using the Debussy's own volume control, with balanced AudioQuest Wild cables feeding the amplifiers and AudioQuest Wild speaker cables hooking up the Harbeths. Paul Simon is singing "Hearts and Bones," ripped in Apple Lossless from Negotiations & Love Songs (CD, Warner Bros. 25789-2). It is hard to believe the hi-fi experience can get any better than this. I know that's not the way the world is, baby, but at this moment, it is all I need.

There seems to be a feeling in some quarters of audiophilia that to get state-of-the-art amplifier sound and performance, you need to pay many tens of thousands of dollars for a product made in tiny numbers from an equally tiny company. By contrast, the Classé CT-M600 and CA-M600 come from a mainstream manufacturer, though they are still expensive amplifiers. But they are nowhere near as expensive as the artisanal models, and they are the best-sounding amplifiers I have auditioned in my system. It is going to be difficult to let them go. Maybe I won't.

Classé Audio
5070 François Cusson
Lachine, Quebec H8T 1B3
(514) 636-6384

tmsorosk's picture

I went out and auditioned a pair of CT-M600s after reading the review . It's hard to say much about the sound under those conditions , the system as a hole was impressive , I can say they sounded superior to the higher priced amps we heard at the same time , same everything . I won't mention what the other amps were , as I'm sure there large following would take issue .
Sure look pretty . Tim

300Binary's picture

I will keep reading your stuff - forever :)

In 1963, I heard a home system that was some big turntable, a tube preamp, a large mono tube amp and a huge VOT speaker.

I thought it was perfect (I was sixteen).

Perfect keeps getting better.

Life is not fair, thankfully.

PS I notice the picture is of the ugly one... nobody's perfect.

soulful.terrain's picture

Great review of the awesome Classe product. I have never listened to a Classe product without being impressed. Also, Classe products are amazingly reliable over the long term.

The only thing I dislike about the new CT series amps are the cosmetics. I feel Classe has taken a step backward in this area.

Mark Evans

Trickster's picture

I agree, the Delta series is way better looking than the Custom Theatre series. I don't mind the Sigma's look though.

Staxguy's picture

I had the occasion to listen to a pair of the Classe CT-M600's monoblocks with the CT-SSP pre-processor, driving a pair of B&W 803 Diamonds, in what was described as a great sounding room, and the sound was utterly horrendous - Bose would be a good description, but that doesn't give Bose enough credit - really! I was looking for a modern version of the old Aragon 8008BB that could drive dynamic B&W's to decent bass levels, and the Classe was recommended.

Was it the new 803 Diamonds that are "terrible"??? The Classe pre-dual-mono combo, the room, or the ensemble, I can not say, but I would derive much more pleasure for the old Matrix 801's, coupled with even similar vintage Rotel electronics, than I could with this combination. I have heard good things about the new 800/802 Diamond models, but it is a shame there was not a newer model similar to the older Matrix 800, to drive a decent amount of air for real-level listening.

The only hi-brand unknown piece of the combo was some random Blue Ray disc player, fed digitally into the Classe CT-SSP. Jitter, possible, in such a modern design, could it be?

Being a Canadian, I had hoped the Class would deliver the goods, but it would not stand even a cursory listening.

I like the low-power consumption in standby mode, which is mentioned in the review, a plus for a relatively larger-powered hi-fi amplifier.

Internally, the CT-M600 looks like a decent amplifier. Externally, the Classe Omega mono looks like a more fitting replacement for the ML 33H to my eye. Could the same designers have had a hand in the design?

Staxguy's picture

I had an occasion to listen to the -new- version of the CT-M600's, driving the new diamond B&W 802's, with a $5000 Classe CD Player, and a sub-$2000 Rotel pre-amp put in temporarily until the replacement $5500 Classe unit arrived, and, in a treated room, it was fantastic.

Great depth of stage for even solo voice, and less "CD player" sound than I had heard on a Sasha W/P / top Naim stack, at medium volumes. At medium-high levels, on decent modern tracks, the 802's driven by the CT-M600's really sounded as if they were augmented by a pair of nice subwoofers - much nicer than my old Velodyne F1500R in terms of fast and tight (and tunefull) bass response. That the 802's did this level of bass in a fairly small cabinet was fantastic, and totally unexpected, but the credit must go quite equally to the Classe CT-M600's.

At moderate levels, though, the meters read at about the 6W level, which really shows how far good, clean power goes.

The sound was still hi-fi, and cleary recorded, but the bass, dynamics and sound staging were a cut above the level. Voice was also quite natural, approaching the level of my understanding, with nice natural sibalance, etc. and tone. There was upsamling going on at the CD player, but this was clearly above-par 16-bit performance for the CT-M600's driving the 802's, even with a "substitute" Rotel pre-amp in the chain.

Listening to this setup, I could clearly hear what the blog entry of John Atkinson had to say.

Earlier in the session, I also listened to the competing McIntosh MC601 600W pair, which were much more imposing visually, and also sounded fine. Will definitely need to see what they each do, on the same material and gear, to make a decision, one over the other.

The new McIntosh 601's drove a pair of Sasha W/P's much more well than a all-NAIM stack with all the power supplies, and sounded much more musical on medium to high levels with them.

Anyone purchasing either amplifier pair should be quite happy, I imagine, unless their hearing is much more rarefied than mine.
The MC601 monoblock pair is the first McIntosh mono-amp than I can stand, driving Wilsons.

Funny that a pair (even older) of the CT-M600's would have sounded absolutely hideous with a B&W 803 diamond pair, while a newer pair of CT-M600's would sound really, really good on a pair of 802's (one step up speaker wise). I would imagine that the DAC design in the Classe SSP would be similar to that of their CDP, and top of the line Transparent Cable was in use on both systems.

I wonder how much better the new version CT-M600's would drive the latest 800's over the 802's, and if the bass would be as fast and sufficient as I heard today.

tmsorosk's picture

I was ready to pull the trigger on a pair of these till I found out Classe' had moved their manufacturing facility from a well regarded Canadian plant to a not so well regarded ( where audio is concerned ) country. I wonder if Stereophile will follow up there review to see if there's a sonic difference.


                                                              Regards  Tim

Trickster's picture

I recently had an in-home audition of the CA-2300 with the CP-800, driving my B&W 803Ds. The sound blew away my McIntosh MA7000. Yes... I know its unfair to compare an integrated with a 2-channel, but this was an incredible difference in every listening category. Unfortunately, my PSA-5 shut things down midway through the audition, but once we plugged straight into the wall, the power seemed limitless. I wonder how well the Classe's M600s would do against the McIntosh MC601s? M600's are almost half the price of the MC601s. Does that mean McIntosh is twice as good?

To all the outsourcing critics... You put a North American assembled Classe amp on the bench right next to one assembled in China and you would see no technical or visual difference. The only difference would be in the price tag.