Disc Players

While Métronome's new SACD/CD player employs the same Asahi Kasei 'Velvet Sound' AK4497 DACs as its DSC1 network audio player [HFN Apr '18], only the AQWO offers access to the DAC's six in-built digital filter algorithms – Sharp/Slow/Super-Slow, Short Delay Sharp/Slow and Low Dispersion Short Delay roll-offs [explored in our review of the Teac UD-503, HFN Apr '16]. Tested in its default Sharp Roll-off mode – a linear-phase digital filter offering 70dB of stopband rejection (re. 22kHz at 48kFs) – the response 'shapes' do not correspond to those of the DSC1 and also differ substantially between the solid-state (SS) and tube output options.

Distortion increases substantially over the top 40dB of the player's dynamic range via the tube option, so while a minimum of 0.0003% is achieved via the SS output from 200Hz-20kHz at –20dBFs, the figure via the triodes is 0.04%/1kHz and 0.14%/20kHz at the same level [see Graph 1, above]. Distortion is high at low frequencies via both outputs – 0.4%/20Hz via SS and 40%/20Hz/0dBFs via the tube out although the source impedance is better managed via the former: 55ohm vs. 600-1140ohm (tube). The A-wtd S/N is substantially wider via the SS output at 116dB vs. 96dB (tube) re. 0dBFs, although the peak output levels are similar at 6.2V vs. 5.85V (tube) via the XLRs.

Not only is this S/N wider than that achieved by the DSC1 network player, so too is jitter very much better suppressed. The figure of 315psec via CD is only 200psec over the minimum achievable 16-bit level and remains comparable to the 340psec measured for 48kHz/24-bit LPCM inputs. Lowest jitter is via SACD at 225psec [black spectrum, Graph 2 above]. PM