LAB REPORT: DARTZEEL NHB-458 (£75,000 each)

摘要

DarTZeel's circuit philosophy - its massive power supply, its use of few active devices, limited local feedback and no Zobel network - is reflected in its technical profile. Power output is ably supported by the 2kVA toroid, besting its 450W/8ohm specification at 580W/1010W into 8/4ohm loads and rising still further to 620W, 1185Wand 1975Winto 8, 4 and 2ohm loads under dynamic (rnusic-like) conditions. DarTZeel's protection circuitry limits output to 276W into 1 ohm loads [see Graph 1, below], there also being a slight loss attributable to the moderate but very uniform 0.3ohm output impedance. Into purely resistive loads, the NHB-458's response is equally uniform and extremely extended - dropping less than 0.5dB at 100kHz and at a near-DC 1 Hz. Any DC offset is low enough at 15mV while hum and noise are squeezed to remarkably low levels, bearing in mind the size and proximity of the supply, at just -76.3dBV (0.15mV, unweighted). The A-wtd S/N ratio is above average at 87.2dB (re. OdBW).