McIntosh MA252 Integrated Amplifier Lab Report

Lab Report

The combination of McIntosh's 'Power Guard' and 'Sentry Monitor' protection regimes are remarkably effective at preventing the MA252's output stage from 'clipping' much beyond 1% distortion no matter how hard the MA252 is pushed. However, the maximum dynamic power output figures recorded here of 152W, 285W, 155W and 52W (into 8, 4, 2 and 1ohm loads) are still entirely representative of what might be achieved in a real system [see Graph 1, below]. Also, with full power outputs of 2x125W/8ohm and 2x200W/4ohm comfortably exceeding McIntosh's 100W/160W rating, it's clear that while the MA252 is powerful it's not especially tolerant of difficult loads and is ideally partnered with loudspeakers offering a 6/8ohm nominal load. The triode/power amp PSU also generates a little extra noise so the A-wtd S/N ratio is also slightly below average at 80dB (re. 0dBW), but this will only likely become apparent with super-sensitive speakers.


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 8.8A


Distortion versus extended frequency from 5Hz-40kHz at 10W/8ohm (left, black; right, red)

Otherwise the MA252 is a model citizen, offering a very wide bandwidth (frequency response) with mere ±0.5dB limits over a 8Hz-100kHz span. The low 0.04ohm source impedance holds through bass and midrange as does distortion which stays below 0.002% from 20Hz-10kHz at 10W/8ohm, increasing to 0.008%/20kHz. The lowest distortion is through midrange frequencies at 5-20W output where it drops to ~0.0006%, increasing to the previously mentioned 0.002% at lower (1W) and higher (60-100W) power outputs. Either way, THD is very well managed within the MA252. The digitally-governed volume control offers excellent channel balance (0.04dB at 0dBW) and channel separation is also very good at >80dB across the audioband. PM

Power output (<1% THD, 8/4ohm) 125W / 200W
Dynamic power (<1% THD, 8/4/2/1ohm) 152W / 285W / 155W / 52W
Output imp. (20Hz–20kHz/100kHz) 0.038–0.061ohm / 0.31ohm
Freq. resp. (20Hz–20kHz/100kHz) –0.1dB to –0.05dB/–0.38dB
Input sensitivity (for 0dBW/100W) 55mV / 566mV (balanced)
A-wtd S/N ratio (re. 0dBW/100W) 79.5dB / 99.5dB
Distortion (20Hz-20kHz, 10W/8ohm) 0.0011–0.008%
Power consumption (Idle/Rated o/p) 34W / 356W
Dimensions (WHD) / Weight 305x194x457mm / 12.7kg
Price £4500
McIntosh Labs
Binghamton, NY, USA
Supplied by: Jordan Acoustics, Bournemouth
01202 911886