Network Audio Players/Servers

While the RS520's (analogue) performance is dominated by the GAN-FET Class D output, it's clear HiFi Rose has 'tweaked' the ultrasonic behaviour of its 250W module since we tested the RS180 [HFN Jul '22]. There's still a modification in HF response with speaker loading but there's also more filtering here, so the RS520 is flat to within ±0.1dB up to 20kHz but rolls away to –22dB/100kHz/8ohm (–0.4dB/20kHz and –25dB/100kHz into 4ohm). The filtering is also reflected in the higher o/p impedance (0.38ohm/20kHz in the RS180 to 0.46ohm here) and the wider A-wtd S/N ratio (67.5dB to 74.5dB re. 0dBW here). Distortion is low enough at 0.004-0.06% through midrange and treble at 10W/8ohm but is higher at low frequencies (0.4%/20Hz). Power output remains on track at 2x250W/8ohm and 2x450W/4ohm, lifting under dynamic conditions to 500W/4ohm, 428W/2ohm and 235W/1ohm – rather higher into the lowest impedances than achieved by the RS180 [8.6A to 10.0A here, see Graph 1].

The RS520's ES9038PRO-based DAC/pre stage is very 'clean', offering a wide 109dB A-wtd S/N ratio from a maximum 2V o/p and 333ohm source impedance. There's some slight phase noise revealed by the jitter tests but correlated sidebands are suppressed to a very low <15psec (all sample rates). Resolution is good to within ±0.2dB over a full 100dB dynamic range and distortion falls from 0.002-0.0017% at 0dBFs (20kHz-20kHz) to a minimum of 0.0004% over the top 30dB of its dynamic range [Graph 2]. The various 'Fast' filters offer the flattest responses – within ±0.3dB to 20kHz, 45kHz and 90kHz with 48kHz, 96kHz and 192kHz files, respectively – with the 'Slow' filters falling to –3.5kHz/20kHz (linear) and –5dB/20kHz (minimum phase). PM