Classé CA-M400 Mono-Bloc Amplifiers (Hi-Fi+)

Solid-state power amplifiers
Classe Audio CA-M400
Classé CA-M400 Mono-Bloc Amplifiers (Hi-Fi+)

Just as the cars of the world are being downsized in engine terms and having every last ounce of power extracted from them in an attempt to appease the carbon religion, amplifiers are slowly but surely becoming more powerful, the most successful examples still relying on good old-fashioned linear power supplies and ever bigger transformers. At 400 Watts per channel Classé’s flagship mono-blocs, twin pinnacles of their Delta series, might once have been considered OTT; now they’re almost me-too.

The distinctive broad radii and contrasting colours of the Delta components are the work of Morton Warren, a name you may recall from the time when Bowers & Wilkins (which owns Classé) launched its original 800 series. He is the industrial designer who came up with those curvy speakers and he has continued that theme with the Delta series. But the casework is more than just attractive it is also designed to isolate the electronics from vibration – internal and external. Classé point out that as electronic components pass a signal or charge and discharge, it generates mechanical energy which in turn becomes a low-level addition to that signal. This is made worse by the intrusion of external energy, much worse if the equipment is placed close to the speakers. Working to eliminate these effects should generate lower distortion, greater clarity and more consistent performance.The Delta casework is a combination of steel and aluminium, with large isolating feet made from soft, Navcom material, the latter tuned to each amp’s massive 37kg bulk.

Whilst in the dim distant past, Classé products were indeed Class A, that’s no longer the case, although their Class AB output stages run to about a third of their rated output in unswitched mode. They also double their output into half the load, so would seem to promise the best of both worlds, high power without the heat. The CA-M400 has both balanced and SE inputs but you need to switch between the two on the front panel. Other back panel connections are for 12v triggers, firmware updates and Classé’s bus system. Internally Classé has incorporated three types of transistor, so there are J-FETs in the input stage, MOSFETS in the driver stage and bipolar output devices. The choice of multiple transistor types is made to capitalize on their relative strengths and conceal their weaknesses. A JFET input stage is easy to drive, relatively insensitive to interconnect cable variances, with very low distortion and very low noise. The JFET is an excellent voltage gain device. It cannot, however, deliver the current necessary to drive a proper output stage, let alone a loudspeaker. So MOSFETs are used after the JFETs to deliver both voltage and current gain. The MOSFETs can easily drive the bipolar output stage, which is widely recognized as being ideal for linearity and high current. How high? The output stage is limited to a mere 90 Amps maximum, a protection measure that’s seen a zero failure rate in the field, despite the several thousands units in use.

As I use the top of the line Classé CP-700 preamplifier at home, the CA-M400s fitted right in. As you might expect with this much power on tap one thing you are guaranteed is an assured and relaxed sound. The CA-M400 is unlikely to break a sweat driving the majority of loudspeakers and will only have to try if it needs to fill a large room using insensitive transducers. But power can often be a barrier to the more subtle musical elements of audio reproduction, it is often suggested that the lower the power the more nimble and dynamic an amplifier tends to sound, at least this is the thinking of many in the glass audio appreciating fraternity. So it was heartening to find that this pairing has an impressively light touch for its class. It doesn’t impose a bone crunching bass on the sound, nor does it seem sluggish. What it does sound is effortless and luxurious, and while these are attractive qualities they do suggest a degree of smoothing that might not expose the finest of details. With the wrong choice of cable this might well be the case, I tried a couple of balanced pre/power interconnect cables before picking the skinny but high resolution van den Hul Orchid. This cable’s character is on the light side; its strengths lie in timing and imaging and in some systems its bass might be a shade lean. With these amps it proved the perfect match, the power amp having no trouble in extracting trouser flapping, sofa shaking low registers and revelling in the definition it brings to leading edges. The speakers it was charged with manipulating were my usual B&W 802Ds, making this a real family affair.

The CA-M400 is primarily about control, something it exerts in a remarkably calm yet revealing fashion. Some will feel that this sounds like a lack of dynamics but in truth it means that the amp can deliver all the required power without having to resort to the distress that can make a system sound exciting but which is in fact a mild form of clipping. There is an awful lot of headroom on offer, which means that it can produce high levels with a degree of ease that’s not available with lower power designs. You may have seen a power requirement calculator produced by Musical Fidelity last year which allows the dialling in of your speaker’s sensitivity and your amplifier’s power giving a result that says how well matched they are. It seemed a little crude to me but is essentially correct because its indication is that we need more power to drive our systems without pushing them into the red than most of us would imagine.

The CA-M400 are also extremely transparent and have an uncanny ability to peel apart the elements in a recording to reveal precisely what each one contributes, without making the sound seem analytical. These amps are in fact extremely strong on detail but it presents the finest nuances in such an effortless fashion that your attention is never distracted from the music and its underlying message.

Inevitably the power on tap makes itself apparent in the bass. At this all important end of the spectrum the CA-M400s deliver low frequencies that surprise with their weight. There’s no suggestion of emphasis, it’s not particularly speedy or hard edged, nothing about this amp is, but it is realistically strong and purposeful. Having used a 200 watt Gamut D200 for many years it was quite surprising to find that the Classé clearly outguns it with the doubling in power. There was a time not so long ago when 200 watts was considered overkill, yet if you want to get the low frequencies from a B&W 802D to imitate a big active loudspeaker it would seem that there’s no substitute for wattage.

To put things into perspective I happened to have a pair of Bryston’s even more powerful 28B SST monoblocs at the same time that the Classé were in the house. The 28B is a 1000 Watt amp, with each channel costing over two grand more than a CA-M400 so the fact that it resolved more of the space in a recording and more substance in voices came as no great surprise. The difference was not enormous, but the bigger amp does produce extra grip and has more overall transparency, suggesting that the Classé is a little soft through the mid-band. Just don’t forget that price differential. The usual competition at the CA-M400’s price includes the likes of Krell, Mark Levinson and home grown brands such as Chord Electronics, most of which tend to be a bit more emphatic in terms of character. The Classé system does not make a big thing about grip, speed or slam. Instead it goes about its business in a remarkably neutral and unprepossessing way. This means that the music has a better chance than usual of doing precisely what the artist, producer and mastering engineer had in mind. It also means that differences between musicians, instruments, recordings et al are very clear. As previously mentioned the smoothness on offer can give the impression that clarity is not as great as it might be, yet when you turn up the wick the presentation remains precisely the same, there is no sense of edginess or strain and as a result high level listening is far more comfortable than usual.

Classé has produced an excellent blend of power, resolution and musicality at what is a competitive price for the build quality on offer. You might not think that you need 400 watts but if a reasonably realistic facsimile of anything bigger than a chamber orchestra is what you are after at home you are probably wrong – especially when it is delivered with this much class.

blog comments powered by Disqus

Featured Articles