Constellation Centaur II Stereo Power Amplifier Lab Report

Lab Report

Taken at face value, the '250W' Centaur II Stereo should be half the amplifier that the Centaur II 500 [HFN Dec '19] represents but, in practice, the 'little brother' punches very close to its slightly newer sibling. Let's compare the figures: the '500W' Centaur II 500 delivers 2x585W/8ohm and 2x930W/4ohm, boosted under dynamic conditions to 685W, 1.25kW and 1.69kW into 8, 4 and 2ohm but 'limited' to 880W (or 29.7A) into 1ohm. The original Centaur power amp [HFN Jul '13] offered 2x510W/8ohm and 2x825W/4ohm with 570W, 1.06kW, 1.93kW and a full 3.01kW (54.9A) into 8, 4, 2 and 1ohm under dynamic conditions. The Centaur II Stereo smashes its 250W rating with 2x400W/8ohm and 2x675W/4ohm, increasing to 425W, 780W, 1.26kW and 856W (29.3A) into 8, 4, 2 and 1ohm under dynamic conditions [see Graph 1, below]. So, in practice, the Centaur II loses nothing to the Centaur II 500 in its ability to drive the lowest impedance loads.

The novel N-type power amp circuit is sufficiently stable into any likely speaker load that no Zobel, or other filter network, is fitted to the output. Output impedance is a very uniform 0.032ohm (20Hz-5kHz) increasing gently thereafter to 0.041ohm/20kHz while the response is super-flat and extended (±0.5dB from sub-1ohm to >100kHz). Stereo separation is an excellent 115dB (1kHz) to 88dB (20kHz) and the 0dBW-rated A-wtd S/N is 87.1dB (Balanced) and 99.1dB (Direct) where the gain(s) are +26dB and +12dB, respectively. The enriched bias keeps distortion below ~0.01% up to around 70W/8ohm after which it increases to 0.015%/100W, 0.05%/200W and 0.085% at the rated 250W (all 1kHz/8ohm). PM


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 29.3A


Distortion versus frequency versus power output (1W/8ohm, black; 10W, pink; 100W, red)

Power output (<1% THD, 8/4ohm) 400W / 675W
Dynamic power (<1% THD, 8/4/2/1ohm) 425W / 780W / 1.26kW / 856W
Output imp. (20Hz–20kHz/100kHz) 0.031–0.040ohm / 0.12ohm
Freq. resp. (20Hz–20kHz/100kHz) +0.00dB to –0.04dB/–0.30dB
Input sensitivity (for 0dBW/250W) 1414mV / 2290mV (Balanced)
A-wtd S/N ratio (re. 0dBW/250W) 87.1dB / 111.0dB (Balanced)
Distortion (20Hz-20kHz, 10W/8ohm) 0.007–0.027% (Balanced)
Power consumption (Idle/Rated o/p) 140W / 945W (4W standby)
Dimensions (WHD) / Weight 432x280x508mm / 44.5kg
Price £54,998

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