At the moment, I use DSP and up-sample MQA using ‘The power of 2’ and set to ‘maximum sample’ in the DAC setting in Roon, and also select ‘Smooth Minimum Phase’ filter. I’m using my Holo Spring DAC set to ‘NOS’ mode.
Critical listening, I notice this setting produce the most natural sounding; especially for vocals, it takes out the slight edgy away. I’m not sure this process is doing some kind impulse optimisation (de-blurring). I also find out that actual ‘rendering’ process is actually ‘up-sampling + de-blurring filter’ applied before going to the DAC, Let me quote from the article above.
'The first unfold of the file, gives you the file as recorded in the studio, this is what Roon and Tidal do. Two things happen at this moment, the unfolding of the file (for example from 16 bits/44.1kHz to 24 bits/88.2 kHz) and to apply a correction of the impulse behaviour of the ADC. Older recordings are known, especially those recorded at 44.1 kHz or 48 kHz used to have steep filters which impacted the impulse behaviour. As a result these filters cause pre and post ringing which create a less natural sound.
The second unfold is geared toward correcting the impulse of the digital to analogue converter. This process is dedicated because every single DAC has its own behaviour. Especially the oversampling DAC’s use steep filtering but this all depends per DAC, more or less. Aforementioned filters are always applied just “above” the music and do have a negative impact on the impulse behaviour. To solve this one can suppress the filter by using up-sampling technology, as an example the unfolded file of 96 kHz is being up-sampled to 192 kHz or even 384 kHz sampling. As a result the filter is being detached from the music and the filter becomes less steep, but still steep. Up-sampling often creates artifacts, but these are considered less annoying than steep filtering’.
@brian , will be possible for Roon to do its custom ‘renderer’ inside DSP just for MQA?