Outboard DACs

A maximum of six digital filters are offered on the Lina DAC X for LPCM inputs [see Graph below: F1, black; F2, red; F3, cyan; F4, green; F5, orange; and F6, purple] although only the first four are available for intermediate 48kHz-176.4kHz sample rates. Your choice of filter impacts both frequency response, time domain distortion (ringing) and stopband rejection, the latter arguably of less significance at higher (96kHz+) sample rates. F1-F6 all deliver a ruler-flat ±0.02dB (20Hz-20kHz) response with CD media albeit with variable stopband attenuation (125dB, 35dB, 12dB, 6dB, 125dB and 120dB, respectively). All except F5 – a fast minimum-phase filter [orange traces] – are linear phase types, although F6 employs fast apodising/linear phase coefficients [purple traces].

In practice, F6 produces the same –3dB/48kHz response as F3 [cyan] despite the latter being a slow roll-off linear phase filter with much reduced stopband attenuation. F1-F4 offer –3dB response limits of 43kHz, 46kHz, 28.5kHz, and 36kHz, respectively, with 96kHz media, and 79kHz, 80kHz, 48kHz and 58kHz, respectively, with 192kHz files with F4 [green traces] offering the least ‘ringing’. The minimum phase F5 has the most pronounced treble roll-off with 192kHz media at –3dB/28kHz. Incidentally, these coefficients are applied before DSD and DSDx2 upsampling and have –3dB limits set at 78kHz, 68kHz, 64kHz, 30kHz and 29kHz (DSD) and 79kHz, 78kHz, 78kHz, 60kHz and 57kHz (DSDx2), respectively. PM