Pre/Power Amplifiers

Modular Magic
All Constellation power amplifiers share a common, and very successful circuit 'concept' – a 125W/8ohm power module employing N-type MOSFETs (rather than complementary NPN and PNP pairs) in a single-ended configuration. Inside the Centaur 500 II there are four pairs of 125W modules in a balanced/bridged configuration, delivering the rated 2x500W/8ohm. In this respect the new Centaur II 500 takes its design cues from the 250W Centaur II Stereo, albeit with a much-improved transformer and PSU.

The novel power amplifier circuit is sufficiently stable into any likely speaker load that no Zobel, or other filter network, is fitted to the output. Moreover, the balanced/bridged modules are not connected to the 4mm output terminals by wire, but via a sequence of plated copper bus bars bolted together and to the rear of the terminals [see inset picture]! We saw the same in the original 500W Centaur Mono [HFN Jul '13] even though the new stereo Centaur II 500 – like other stereo Constellations – is 'limited' into very low impedances with a reduced current delivery of 29.7A (vs. 54.8A). While the 500 II is hardly bashful, the more affordable Inspiration Monos [HFN Oct '19] are more load-tolerant, sustaining 690W, 1277W, 2.2kW and a full 2.9kW into 8, 4, 2 and 1ohm loads under dynamic conditions (a current reserve of 53.4A). PM