Nah, not that simple. Much recorded music by nature has very little ultrasonic content, so your 95 percent figure of merit might produce spurious results on many recordings.
And how would your bandwidth methodology assess this previously noted MQA example?
AJ
… the day the music died 
it’s not about ‘wavelenths’.
Imagine if digital audio was more clever implemented, with 20 - 20 khz audible frequency, and an independent sample rate not tied to frequency? And then some clever lossless compression on top of that. In a way, MQA is an effort to achieve this (but not sure they succeeded very well).
Not sure this is possible, but coming from the IT world it seems to strange with audio files that pack so much information that is not audible, like it was made for dogs or something 
Fine, so it needs work. Come up with something!
This graph does not show any music content above the audio due to sharp cut-off of the digital filter. It is probably made from a 44.1k master. The noise start to rise above 22.05k is ultrasonic noise and aliasing caused by MQA leaky filter.
A better example is below, showing PCM 192k that extends above 48k bandwidth.
There’s some ultrasonic music contents above 20k bandwidth.
MQA support is now live.
Wow! Very nice. Can’t wait to try it out later when I get home. Thank you so much!
Just to clarify, if using a non-MQA Streamer like an Auralic Aries, Roon will do the first MQA unfold just like the Tidal desktop app?
Yes it will.
The Aries, or any other streamer for that matter, would essentially be completely transparent to the process. Roon will see the DAC via the Aries. If the DAC is a fully-decoding MQA DAC, and no DSP is applied in Roon, then Roon will stream the data undecoded. If you apply any form of DSP in Roon, Roon will:
1- Unfold the data to 2x the original data’s sample rate
2- Preserve the MQA rendering information on the side
3- Apply the DSP to the unfolded (but not rendered) stream
4- Reattach the MQA rendering info to the stream
5- Send that to the DAC via the Aries
If the DAC is MQA compatible, either full compatibility of just renderer, it will render the stream using the MQA-specified filters. The DAC will not (need to) do the first unfold since that already happened in Roon.
BTW… Do we know for a fact that any full-decoding DAC will indeed work as a renderer if a first-unfold is performed in software? I don’t think this is obvious.
The Explorer 2 isn’t at the moment but will when (if) a firmware fix is released.
Yes, the Pro-Ject S2 DAC shows MQB on it’s screen when the DAC is set to MQA renderer mode.
The same way it’s been working when Tidal Desktop App and A+ have been doing the 1st unfold.
Yes I realize the mistake in my original post. I should have stated that I have an Aries and a non-MQA DAC, the Chord Dave. So I will now get the benefit of the first unfold from Roon.
Many MQA USB DAC do. Lumin does when used with Roon. Does your DAC support it?
For those that do not support this feature, Roon Labs have said they’re chasing the manufacturers to get this fixed.
https://kb.roonlabs.com/Roon_x_MQA
I will check when I have a sec. Easy to tell as it would tell me the filter being used is M1.
Actually prob doesn’t matter as the E2 never turns off the MQA filter regardless!
One thought comes to mind: is it now possible to configure Roon to upsample non MQA music, but to disable that for MQA tracks ? Or will that come in a later build?
@Alastair_Roberts It already does that.
My Meridian 818v3 MQA DAC is set up as Decoder and Renderer. Sample Rate Conversion is set to Max PCM rate (Power of 2).
That’s fantastic! Can’t wait to try all of this.
I think (and I have) a slightly different question… Lets say I have a full-MQA decoding DAC (I do, dCS Rossini).
So the questions are:
Can I set DSP to upsample standard PCM to max-power-of-two while leaving MQA untouched?
Can I set Roon to unfold MQA and NOT upsample it (ie letting the DAC do the upsampling via rendering) while upsampling PCM to max-power-of-two?
If I do any other DSP in Roon (such as convolution) - can I still do the same as in ‘2’ - ie MQA --> unfolded --> Convolution (possibly at a very high rate) --> rendering in the DAC?
