Outboard DACs

Implementations of AKM’s two-part noise-shaper/DAC chipset have thus far been mixed [HFN May/Jun ’24 & Jan ’25], but FiiO’s K17 joins Matrix Audio’s MS-1 [HFN Feb ’25] as a superior solution. The K17 realises a maximum 5.16V balanced output from a 70ohm source impedance, delivering a 118dB A-wtd S/N ratio from all digital inputs and with a low-level linearity that’s true to within ±0.1dB over a full 115dB dynamic range. THD falls to a minimum 0.00009-0.0003% (20Hz-20kHz) over the top 30dB of its range [see Graph 1] while jitter is suppressed to <25psec across all sample rates. Stopband rejection and freq. response depends on filter. The sharp linear- and minimum-phase (Fast and Mini) filters have the same –0.5dB/45kHz and –1.15dB/90kHz responses with 96kHz and 192kHz media, respectively, with a similar 104dB stopband rejection, while the slow roll-off (Slow and Mini Slow) types trade a limited 8.5dB stopband rejection and –8.3dB/20kHz, –9.6dB/45kHz and –10.3dB/90kHz responses for minimal ringing/time domain distortion.

The headphone amp has five gain options: Low (–14.8dB), Medium (–8.8dB), High (–5.8dB), Super High (+6.0dB) and Ultra High (+9.0dB), these settings delivering 27mW, 106mW and 210mW for Low, Medium and High with the rated 1860mW achieved into 32ohm in both Super and Ultra High modes [black trace, Graph 2]. The maximum 8.8V output will support a hefty 130mW/600ohm [blue trace] while over-current protection limits power to 910mW into very low 8ohm loads [red trace]. THD is very low at 0.0001-0.0004% (re. 10mW/32ohm) and largely unaffected by loading, while the 1.5ohm source impedance serves a response that’s flat to within ±0.03dB (20Hz-100kHz). Noise is very low and the A-wtd S/N ratio is a wide 101dB. PM