Sound Quality Over Network and Locally - The 'Digital' Question

First post so hope it is in the right place. I’ve read around this but can’t find quite the right answer. Am currently trialling Roon and want to make sure it is right for me. I love the metadata side of it, but driving myself a little mad on Sound Quality.

Mainly the question comes down to optical digital quality. Until getting Roon I was streaming from Plex on a Mac Mini to a Google Chrome Audio, optical out in to a (slightly vintage but nice sounding) Cambridge DAC. Roon doesn’t support GCA so I have used an old Apple TV 3 to test, in to the same DAC. It’s very subtle but I don’t think the sound quality is as good.

However when I play Roon on the Mac Itself, through a UAD apollo direct to the device but with no DSP on some quite revealing monitors, I’m pretty sure it sounds better than Plex or VLAC playing the same files over the system audio.

So two questions are:

Is it possible ATV 3 sounds worse than GCA, isn’t an optical out just transferring the bits? Appreciate this is a little controversial. Either way can I assume an RPI with a DAC would solve at least most of this issue…?

Is it possible that Roon sounds better than Plex on the same system with same output card. Is that somehow because it is going direct to the device and bypassing system audio? Or am I just trying to convince myself to spend money :slight_smile:

Hope this makes sense, thanks in advance for any help.

The ATV3 resamples all 44.1kHz Airplay transmissions internally to 48kHz – that’s quite an ugly conversion. I am not surprised that you are hearing a difference.

A Pi with a Digi+ PRO board will sound at least as good as the GCA – most likely better (less jitter, better clocking). A Pi with a DAC Hat will sound as good as the DAC Hat is. :slight_smile:

Interesting thanks. Any comment at all on the local playing, is there something there that relates to OSX system audio or…?

Your answer is in your question, you think it sound’s better. That is really all that matters. It’s hardly expectation bias as you correctly identified by the same ears the issues with the ATV.

Trust your ears


It’s not the sampe rate conversion that does the most damage, its the lossy AAC-conversion that takes place when streaming to an AppleTV.
AirServer Lossless Quality audio reciever

Interesting, is that how Roon handles it?

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No – lossy AAC is used only when a video is played over Airplay. The article describes a way to force lossless audio when using AirServer.

AFAIK, that audio-only stream (which is employed by Roon) uses lossless ALAC compression @ 44kHz/16-bit.

Perhaps you are correct Rene, but I just assumed that the sending device is responsible for sending the correct format to either of these.
Once upon a time there was a whitepaper available from Apple but it is no more… :confused:

Thanks for the help, going to try it with and RPI