The Classé CA-M400 Mono-Blocs

Monumental Power…

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.

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