Outboard DACs

The tiny switch referring to ‘Measure’ and ‘Listen’ is potentially misleading as you may ‘listen’ to either setting! Moreover, iFi Audio has its screen printing reversed around this little switch, so ‘Listen’ is ‘Measure’ and vice-versa. So it’ll be interesting to discover which, if any, headphone bloggers can hear the difference! In practice, iFi Audio suggests that ‘Listen’ is optimised for transient response while ‘Measure’ delivers the flatter frequency response. The former selects a standard linear phase digital filter [black traces, Graph below] that offers a moderate 53dB stopband rejection and a response that reaches out to –0.27dB/20kHz and –1.5dB/45kHz with CD/48kHz and 96kHz media, respectively. The ‘Listen’ option selects a slow roll-off type, not dissimilar to Pioneer’s interpolative (IIR) Legato Link filter of the 1980s, with its minimal ringing (much reduced time domain distortion) but curtailed treble (–3.3dB/20kHz) with CD/48kHz sources [red traces]. This filter’s reduced acausal distortion may confer some subjective advantage, but the poor (7dB) stopband rejection means I’d recommend it for 96kHz+ downloads rather than 44.1kHz/48kHz files. PM