Pre/Power Amplifiers

The N^o534 power amp is sufficiently richly biased to raise that substantial 56kg casework to 45^oC in various (heatsink) hotspots. It's also more powerful than the 250W/8ohm rating suggests at 300/8ohm and 550W/4ohm, and has headroom for 335W, 638W and 1245W under dynamic conditions into 8, 4 and 2ohm loads [see Graph 1]. Short-circuit protection limits its output into 1ohm loads to 480W. Meanwhile, although the N^o534 uses the same amplifier 'module' as the N^o536 mono block [HFN Sep '16] the bridged/balanced topology of the latter confers a different distortion 'fingerprint'.

ML's specifications do not acknowledge this difference and so both the N^o536 and N^o534 are presented with the same response (10Hz–20kHz, ±0.2dB), gain (+26dB), S/N ratio (>85dB) and distortion (<0.3% to rated output). In practice the N^o534 has a slightly more pronounced HF roll-off (–0.2dB vs. 0.0dB/20kHz), a lower gain (+24.6dB vs. +25.6dB), and slightly lower, but still fabulous, A-wtd S/N ratio (95.7dB vs. 98.7dB re. 0dBW). The differences in THD are more telling: while the N^o536 offers a reasonably consistent 0.0025-0.01% over its 400W bandwidth (at 1kHz), the N^o534's THD increases steadily from 0.0035%/1W, 0.016%/10W, 0.035%/100W and 0.06%/250W. Versus frequency, the N^o536 and N^o534's patterns are very similar, however, and reassuringly 'flat' through the majority of the audioband [red trace, Graph 2]. Distortion via the partnering N^o523 preamp is far lower still at ~0.0001-0.0004% from 20Hz-20kHz [black trace, Graph 2] while the A-wtd S/N is impressive at 97.1dB (re. 0dBV). Maximum output is 21V (balanced), full gain is +13.5dB and the response flat from 3Hz-100kHz (+0.0/–0.3dB). PM

Continuous power (<1% THD, 8/4ohm): 297W / 550W
Dynamic power (<1% THD, 8/4/2/1ohm): 335W / 638W / 1245W / 480W
Output imp. (20Hz–20kHz, pre/power): 74ohm / 0.040–0.048ohm
Freq. resp. (20Hz–100kHz, pre/power): +0.0 to –0.3dB / +0.0 to –2.7dB
Input sensitivity (for 0dBV/0dBW): 211mV (pre) / 165mV (power)
A-wtd S/N ratio (re. 0dBV/0dBW): 97.1dB (pre) / 95.7dB (power)
Distortion (20Hz-20kHz, 1V/10W) : 0.0001–0.0004%/0.016–0.090%
Power consump. (pre/idle/rated o/p): 58W / 315W/975W
Dimensions (WHD, Pre/Power): 438x102x457/451x197x508mm
Prices (pre/power amp): £16,000/£21,000