Disc Players

Conservatively rated at 60W/8ohm, Exposure's XM5 amplifier achieves closer to 2x75W/8ohm and 2x115W/4ohm, increasing still further to 98W/8ohm and 174W/4ohm under dynamic conditions [see Graph 1, below]. Power is limited by electronic protection to 160W and 86W into 2/1ohm loads, so you'll still get the biggest blast from 6-8ohm nominal loudspeakers with the XM5. Otherwise its low output impedance delivers a consistent –0.13 to –1.0dB response (20Hz-20kHz, down to –13.4dB/100kHz) almost regardless of load impedance while the A-wtd S/N is 'average' for the breed at 87dB (re. 0dBW). If you use the XM5 as a DAC/amp then it reaches out to –0.7dB/20kHz but falls more rapidly to –3dB/36kHz and –10dB/47kHz (192kHz media). Digital jitter is a low 75psec – and this is principally PSU-related – while distortion mirrors that of the analogue amp, increasing from typically 0.002% through bass and midrange to 0.10% at 20kHz (re. 0dBFs).

The partnering XM CD player offers a modest 99dB A-wtd S/N from a maximum 2.2V output, while the 97ohm source impedance (rising to 295ohm/20Hz) shows the effect of the cap-coupled output. The response is necessarily limited, although at –0.2dB/20kHz is 'flatter' in the audioband than the XM5 amplifier. Jitter follows the same pattern as that observed with the XM5's DAC but the trend of low bass/mid distortion (0.001% at 0dBFs) increasing at HF (0.02%/20kHz) is milder through the XM CD [black and blue infills, Graph 2]. The linear-phase digital filter option of TI's PCM1716 DAC is used here so there's some limited pre/post ringing on impulses, traded for a useful (but not extreme) 79dB suppression of digital alias distortions. PM