PS Audio Stellar M1200 Mono Power Amplifier Lab Report

Lab Report

Although this latest M1200 monoblock offers exactly the same +30.6dB gain as PS Audio's M700 [HFN Apr '20] its performance differs in several important respects. Power output is necessarily increased courtesy of the 1200-series ICEpower module, from 365W/8ohm and 715W/4ohm for the M700 to 628W/8ohm and 1246W/4ohm here. As expected, the Class D architecture yields no advantage under dynamic conditions, in fact the 'TCCCL' (Temperature-Compensated Cycle-by-Cycle Current Limit) regime actually caps the output at 597W, 1080W and 1985W into 8, 4 and 2ohm, 'falling' to 1311W/1ohm, or 36A [see Graph 1, below]. Either way, the M1200 will not run short of breath...

As we saw with the M700, the M1200 shows a trend of gently rising distortion with increasing output – the triode tube input only adding some slight 'colour' here – from 0.0029%/1W to 0.012%/10W, 0.038%/100W and 0.14% at the rated 600W/8ohm. The 1200AS1 Class D module is optimised for best performance/lowest THD into 4ohm [again, see Graph 1] but distortion is otherwise maintained at an impressively consistent level vs. frequency from 20Hz-4kHz, increasing thereafter to 0.065%/20kHz/10W [see Graph 2]. This new module is quieter than that used in the M700, the 83.9dB A-wtd S/N ratio besting the latter's 76.1dB by some margin. I discuss the M1200's much reduced sensitivity to speaker loading in my boxout, p65, but the practical result is a flat ~0.026ohm output impedance from 5Hz-5kHz, rising only gently thereafter to a maximum 0.83ohm/95kHz (10x lower than with the M700). The frequency response now extends from 2Hz-25kHz (–1dB) and to –0.65dB/20kHz and –7.05dB/100kHz largely independent of loading. PM


Dynamic power output versus distortion into 8ohm (shaded trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 36.2A


Distortion vs. extended freq. at 1W/8ohm (black), 10W/8ohm (blue) and 100W/8ohm (red)

Power output (<1% THD, 8/4ohm) 628W / 1246W
Dynamic power (<1% THD, 8/4/2/1ohm) 597W / 1080W / 1985W / 1311W
Output imp. (20Hz–20kHz/100kHz) 0.024–0.055ohm / 0.83ohm
Freq. resp. (20Hz–20kHz/100kHz) +0.0dB to –0.65dB/–7.05dB
Input sensitivity (for 0dBW/600W) 83mV / 2093mV
A-wtd S/N ratio (re. 0dBW/600W) 83.9dB / 111.7dB
Distortion (20Hz-20kHz, 10W/8ohm) 0.0115–0.065%
Power consumption (Idle/Rated o/p) 29W / 707W
Dimensions (WHD) / Weight 432x95x330mm / 12kg (each)
Price £5999 (pair)

PS Audio
Boulder, Colorado
Supplied by: Signature Audio Systems
07738 007776