Pre/Power Amplifiers

By blending a Class AB output stage with a Class H stepped-rail PSU architecture, Emotiva has engineered a cooler-running amplifier with an electrical efficiency only 10-15% behind that of a modern Class D design [see NAD M33, HFN Aug '20]. Also key to its 'green' equation is Emotiva's decision to eschew a conventional linear PSU, with heavyweight transformer, in favour of a compact, efficient but very high capacity switch-mode PSU, rated at a very substantial 3kW [see inset picture]. With an idle power consumption of just 18W and a (measured) efficiency of 75% at 200W/8ohm output, the XPA HC-1 is able to use relatively modest heatsinking to keep its mere 10kg chassis cool under pressure.

Class H boosts efficiency by switching up to a higher voltage PSU rail only when signal conditions demand it, but the earliest designs would often betray a 'step' in distortion as the PSU switched between rails. Fortunately the XPA HC-1 is entirely free of this side-effect and so, like many amps of any 'Class', its distortion changes progressively and smoothly with level. In practice, Emotiva's Class H is not dissimilar to the Class G regime recently employed by Arcam in its amplifiers, including the latest SA30 [HFN Jul '20]. PM