Network Audio Players/Servers

While Astell&Kern details the choice between AK4499EQ and the pair of ES9068AS DACs within its SE200 player – with a further choice of six and three digital filters, respectively – and each with its own customised headphone amplifier, I could find only a limited published specification of performance. So here are the numbers, independently tested... In practice it's the AKM DAC/headphone output that delivers the higher maximum line-level of 3.13V and the higher, though still modest, 60mW/32ohm power output via its single-ended connection (many full-sized headphone amps deliver in excess of 500mW/32ohm). As the SE200 clips at volume settings above '136' with a peak level (0dBFs) digital input, the dial should be used between 137-150 with caution, not least for fear of potentially harmful in-ear SPLs.

Otherwise the performance of this 'hi-res' player is superb – it offers a tremendous 112dB A-wtd S/N ratio and very low levels of correlated jitter, never exceeding ~5psec with any sample rate up to 192kHz. There is evidence of low-rate, uncorrelated jitter visible in the broadening of the test signal [see Graph 2] but the impact of this in headphone listening is unclear. More importantly, the output impedance is a very low sub-1ohm from 20Hz-20kHz, ensuring that the overall SE200/headphone system response is not influenced by low and variable in-ear/on-ear loads. With its default linear phase filter(s), the response of the SE200 is a very flat ±0.03dB (20Hz-20kHz), dipping to just –0.6dB/45kHz with 96kHz media. Distortion is also vanishingly low at 0.0001-0.001% (re. 0dBV, 20Hz-20kHz), increasing only over the top 25dB of its dynamic range under load (0.0008-0.005% at 10mW/32ohm) [see Graph 1, below]. PM