Mytek Brooklyn Bridge Network-Attached DAC Fun With Filters

Fun With Filters

In common with the original Brooklyn DAC+ [HFN Aug '17], the Brooklyn Bridge is equipped with ESS's customary 'Fast Roll-off' and 'Slow Roll-off' linear and minimum phase filter options alongside apodising, brickwall and hybrid types. With MQA decoding disabled, the 'Fast' linear phase filter yields the familiar pre/post echoes on impulses but offers a full 82dB rejection of alias distortions and a flat response (–0.04dB/20kHz, –0.5dB/45kHz and –1.9dB/90kHz with 48kHz, 96kHz, 192kHz media, respectively). By contrast, the 'Fast' minimum phase filter has no pre-echo, but still offers a very flat response [see black traces, inset Graph] and a useful 75dB alias rejection.


The trade-off is a mild group delay through the audioband and extended post-ringing on the impulse. Interestingly with MQA enabled, but fed a non-MQA LPCM input, the digital filter is revealed as a slow roll-off minimum phase type exhibiting reduced post-ringing but poor 12dB stopband rejection (and clipping at full scale) together with a 'softer' treble amounting to –0.45dB/20kHz, –10.5dB/45kHz and –12.2dB/90kHz with 48kHz, 96kHz, 192kHz media, respectively [see red traces, inset Graph]. PM

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