The announcement on January 5 that Tidal would begin streaming MQA files (and suggestions that many other streaming services would soon follow suit) was accompanied by an unexpected twist—that MQA decoding can be performed in music-player software rather than exclusively in an MQA-compliant DAC. That is, you can listen to decoded MQA with your existing DAC.
MQA had previously asserted that MQA decoding would take place only in MQA-equipped DACs. Although technically possible to perform MQA decoding in music-player software such as Tidal, Roon, Audirvana, etc., MQA prohibited that scenario in part because software decoding doesn’t deliver the full sound quality that MQA is capable of. MQA is an end-to-end system that ties together the analog-to-digital converter in the studio with the digital-to-analog converter in the listener’s playback system. Software decoding, in which the “unwrapped” MQA file is output as a 96kHz/24-bit stream, doesn’t allow this end-to-end connection because the software player doesn’t know what DAC it is driving. The full implementation of MQA (decoding in a DAC rather than in software) offers better performance because it can correct for known limitations and flaws in the particular DAC chip, among other benefits.
In addition, software decoding is limited to a maximum sample rate of 96kHz. Files that were originally at 176.4kHz, 192kHz, or 384kHz will unwrap only to a maximum of 96kHz, not the original sample rate. There is no such limitation with an MQA-equipped DAC.
For whatever political or business reasons, you can now listen to MQA without an MQA DAC, but with the knowledge that the sound will be better when decoded by an MQA-equipped DAC.
In addition to allowing you to hear MQA-decoded files without an MQA DAC, software decoding offers the possibility of a two-step MQA decoding process. In this scenario the music-player software performs the first decoding step and the MQA DAC performs the final steps to realize the full MQA performance. Many DACs or portable DACs operate with this two-step decoding process. Such DACs are more properly called MQA “renderers” rather than MQA decoders. The “half-decoded” signal output from your computer to your DAC contains all the information the DAC needs to complete the full MQA decoding.