Built into the same chassis as the company’s KA S 270 stereo amplifier, the 650 still presents a pretty imposing block. The difference is that at around three-fifths of the cost and two-thirds the size of the 1200 it is rather more manageable (in every sense). Indeed, at a “mere” 50kg it is just about man portable – a comment that will have chiropractors everywhere rubbing their hands in glee. Attempt this and be warned that you are solely responsible for the consequences. Physical parameters aside, the KA M 650s are exactly what you’d expect: the same bluff but beautifully executed casework (including the same hand lacerating heat-sinks), the same fully differential, DC coupled, zero feedback circuitry, the same balanced or single-ended inputs. You of course also get the same captive isolators built into the feet, three of them ensuring the amps get a firm and mechanically close-coupled footing. Inside the packed casework of each chassis is a pair of 960 VA toroidal transformers and 132000 microF of ultrafast reservoir capacitance, feeding the sophisticated ring emitter bipolar output devices. Those huge heat-sinks aren’t just for show; with the driver stages running in class A and the output stages leaning that way, the amps run warm, even in the depths of winter, where they act as pretty effective supplementary space heaters. One other aspect of the 650s adds to their practicality over the 1200. Each amp requires but a single IEC mains lead as opposed to the excessive demands of the larger model, a factor that certainly makes providing a coherent mains supply significantly easier.
The watchword with the 650s has to be “care” – as in “handle with”. Yes, they are physically more manageable than the 1200s but in every other respect they are just as critically revealing. Cable differences (I ran them with Crystal Ultra, and Nordost’s Odin and Valhalla) are shockingly apparent, as are housekeeping issues like the provision of a clean earth and proper support. It’s not that they sound bad without these niceties; the worst you can accuse them of is sounding a little flat if they’re not being fed their preferred diet. But playing with cables, the finite elemente amp stands, even the connection order and polarity of the mains leads into the distribution block all elevate the performance from the merely excellent to the musically spectacular.
There are two inevitable questions confronting the 650s: how do they stack up against the 1200s, and how successfully do they juggle the big amp issues of control versus musicality?