Constellation Centaur II 500 Power Amplifier Lab Report

Lab Report

When an amplifier is bridged to supply twice the volts across a given load, power output typically increases into 8 and 4ohm but can decrease into lower impedances if there's a shortfall in current from the PSU. Constellation has managed this juggling act well enough – the Centaur II coming close to its 500W/8ohm and 1kW/4ohm rating by delivering 585W/8ohm and 930W/4ohm, boosted under dynamic conditions to 685W and 1.25kW, respectively. A full 1.69kW is achieved into 2ohm but output is 'limited' to 880W (or 29.7A) into 1ohm [see Graph 1, below], so while it will surely drive most likely partnering speakers with ease, the brand's monoblocks still have the edge.

Output impedance is a very uniform 0.035ohm (20Hz-5kHz) increasing gently thereafter to 0.049ohm/20kHz. Distortion follows a similar trend with a 'flat' 0.004-0.009% (again, 20Hz-5kHz) at 10W, rising to 0.03%/20kHz in 'Balanced' mode. Incidentally, overall gain is a 'standard' +25.8dB via the 'Balanced' input but falls to +12dB via 'Direct' – a mode that can only usefully be employed with very high (~20V) output preamps. Distortion is also just a little higher in 'Direct' mode [red trace, Graph 2]. Versus level, this low and steady THD is maintained by Constellation's enriched bias up to around 40W/8ohm after which it increases to 0.01%/100W, 0.03%/200W, 0.07%/300W, 0.11%/400W and 0.16% at the rated 500W (all 1kHz/8ohm). Distortion typically increases by x4 for each halving of load impedance [Graph 1]. Frequency response is flat to within ±0.2dB over a very wide 2Hz-100kHz bandwidth (not all Constellation amps extend into the subsonic) while separation is an excellent 110dB (1kHz) to 90dB (20kHz). PM

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Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 29.7A

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Distortion vs. frequency from 5Hz-40kHz re. 10W/8ohm (black, 'Balanced'; red, 'Direct' mode)

Power output (<1% THD, 8/4ohm) 585W / 930W
Dynamic power (<1% THD, 8/4/2/1ohm) 685W / 1.25kW / 1.69kW / 880W
Output imp. (20Hz–20kHz/100kHz) 0.032–0.049ohm / 0.21ohm
Freq. resp. (20Hz–20kHz/100kHz) +0.00dB to –0.01dB/–0.18dB
Input sensitivity (for 0dBW/500W) 144mV / 3265mV (Balanced)
A-wtd S/N ratio (re. 0dBW/500W) 90.6dB / 117.6dB (Balanced)
Distortion (20Hz-20kHz, 10W/8ohm) 0.003–0.028% (Balanced)
Power consumption (Idle/Rated o/p) 229W / 1.73kW (5W standby)
Dimensions (WHD) / Weight 476x292x616mm / 68kg
Price £64,998

COMPANY INFO
Constellation Audio
Newbury Park, CA, USA
Supplied by: Absolute Sounds Ltd
0208 971 3909
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