iOS playing hi res with Roon and no external DAC?

alessandro_niola · May 20, 2018, 7:21am

Good morning
I am playing some MQA using my iPad and to my surprise the signal path is showing as lossless with an MQA 88.2 authentication.
Here is the path, marked as lossless :
Source : Tidal FLAC 44.1kHz 24 Bit 2ch, MQA 88.2khz
Authentication: MQA Studio 88.2Khz
This Tablet: Roon Advance Audio Transport
Apple iPad: Headphones

I knew that iOS devices were limited to 24/48 but this does not seem to be the case.
Anyone here experienced something similar?

thanks
Ale

Martin_Webster · May 20, 2018, 8:55am

I can’t replicate this. Anything over 24/48 undergoes conversion on my iPad (11.1.3.)

alessandro_niola · May 20, 2018, 9:45am

Thanks @Martin_Webster
Aren’t the 2nd and 4th screenshots showing a lossless path for hi res files ?

Martin_Webster · May 20, 2018, 9:58am

Yes, that’s correct. However, these are MQA and when unfolded they are 96/24 (2 x 48) not the authenticated sample rate.

The oddball is the native 96/24 which undergoes some conversion.

alessandro_niola · May 20, 2018, 10:05am

Good point on native 96/24
but for MQA I would expect the same behaviour given the iPhone DAC limitation to 24/48…

Martin_Webster · May 20, 2018, 11:37am

I’m not sure what’s happening here. It would see that iOS is limited to 48/28, but I’d expect that to be indicated with the MQA files too. There are hints online that 96/24 is now supported, but I can’t find anything conclusive from Apple on this topic.

AndersVinberg · May 20, 2018, 3:43pm

Screenshots 2 and 4 show MQA authentication to 96k (“yes, this is genuine MQA source file”) but it doesn’t show MQA unfolding to 96k because Roon knows that the endpoint can’t do that.

Martin_Webster · May 20, 2018, 3:53pm

Of course no unfolding takes place … thank you.

With a DragonFly we have an extra step in the Signal Path:

alessandro_niola · May 20, 2018, 4:55pm

ok, so what miss is the “MQA ore decoder” step, I see.
But I would not expect a “lossless” tag in this case because there is a quality ross from source to endpoint.

AndersVinberg · May 20, 2018, 5:03pm

Yeah, but not in Roon.
You could argue that the original source was 96k and MQA folded it down to 48k and leaving it like that is a loss.
But Roon describes its world, and from the time Roon got the 48k stream it was delivered losslessly.
Without the possible improvement, because of the iOS bottleneck. But the system didn’t introduce any losses.

Anyway, a USB connected DAC solves it.

alessandro_niola · May 20, 2018, 5:06pm

Thanks, I do have a USB DAC which is MQA capable, but I was just wondering why the signal path was looking like that without the DAC.

however I am not sure Roon describes its world only.
When you stream to a Sonos you will see roon downsampling to 16 bit as that is the maximum format accepted by the end point. The signal path will be green/high quality.
Same for a native high res file using an IOS device as an endpoint.

So when I use an iOS device without the USB DAC I would expect Roon to authenticate the MQA, downsample it to 16/48 and show the signal as high quality.

Am I wrong?

Martin_Webster · May 20, 2018, 5:54pm

I’m learning that Roon understands quite a bit about connected endpoints and adjusts the settings for best results. In this case, your iPad can play 48/24 so no need to downsample.

If you look at the last image I posted (from my MacBook) the source file is 48kHz (TIDAL FLAC 48kHz 2ch, MQA 192kHz) and Roon decodes to 96kHz 24bit. If I play this on my iPad (last image from previous post) there is no decoding stage so Roon is passing through 48kHz 24bit.

alessandro_niola · May 21, 2018, 7:15am

thanks Martin, that clarifies my doubt!