Mark Levinson No523/No534 pre/power amplifier Lab Report

The No534 power amp is sufficiently richly biased to raise that substantial 56kg casework to 45oC 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 No534 uses the same amplifier 'module' as the No536 mono block [HFN Sep '16] the bridged/balanced topology of the latter confers a different distortion 'fingerprint'.


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 25.0A


THD vs. extended freq for No523 preamp (1V out, black trace) vs. No534 amplifier (10W/8ohm, red)

ML's specifications do not acknowledge this difference and so both the No536 and No534 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 No534 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 No536 offers a reasonably consistent 0.0025-0.01% over its 400W bandwidth (at 1kHz), the No534's THD increases steadily from 0.0035%/1W, 0.016%/10W, 0.035%/100W and 0.06%/250W. Versus frequency, the No536 and No534's patterns are very similar, however, and reassuringly 'flat' through the majority of the audioband [red trace, Graph 2]. Distortion via the partnering No523 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

Harman International Ind.
Northridge, CA, USA
Supplied by: Harman Luxury Audio Group (UK), Cambridge
01223 203200