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RE: But what about...?

Hello Doug,

Someone just brought a post to my attention (linked below). This is from Gordon Rankin, who designed the award-winning AudioQuest DragonFly series of USB DACs. The latest two models have been designed with MQA in mind and last week a firmware update was released that allows for some sort of MQA compatibility.

I must say that I don't yet understand this process. Remember that software decoding of the first "fold" was a surprise only announced when Tidal began streaming MQA in late January. This is the first I've heard of "custom filters for each song" and leaves me with more questions than answers:

1) If there is specific filtering done for each song, why not do it during the encode process?

2) The scheme is very reminiscent of similar schemes patented for the A/D process by Pacific Microsonics for HDCD and for the D/A process by Ed Meitner and assigned to Museatex for the BiDAT DAC. Both processes had two separate filters (anti-aliasing for the A/D side and reconstruction for the D/A side). The units would automatically switch coefficients depending on the signal level in the top octave. Is there more to this in MQA's implementation? How many sets of filter coefficients are available?

3) The DragonFly DACs will not normally decode signals higher than a 96kHz sample rate. My understanding is that the software decoding performed in the Tidal software only outputs a maximum sample rate of 96kHz. Does the DragonFly do anything more than fine-tune the filter coefficients?

It would seem that MQA is still under development. Interesting times. As always these posts are my opinions only and not necessarily those of my employer or previous employer.

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Follow Ups
  • RE: But what about...? - Charles Hansen 09:56:48 05/25/17 (0)


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