Pass through highest quality audio always?

[DylanBuffum]

I have Plex Media Server running on a 2012 Mac mini. It contains a wide variety of audio and video, some in high-res formats.

I play the media on a Denon AVR-S540BT, which has a whole slate of options for decoding the digital signal. Some are only available if the original signal is in that format (for example, Dolby TrueHD is only an option for output if the input signal is Dolby TrueHD).

I use a variety of routes to get the audio/video from the server to the AVR.
→ Plex on an Apple TV connected by ethernet
→ Plex on iOS which I airplay to the Apple TV
→ Plex on iOS sent to the AVR by Bluetooth
→ Plex on an Amazon Fire Stick connected to the LAN via WiFi

→ I’m considering an AirPlay dongle as another possible option.

I want to make sure that Plex is always sending the original, highest quality data to the Denon AVR, and let the AVR do the work of properly decoding it according to its settings. If a file is FLAC 2-channel, I want the Denon to get a FLAC file. If the file is AAC 5.1 channel, I want the Denon to get AAC 5.1 channel. If it’s PCM, I want PCM at the end. I’m particularly interested in audio, but video too. If it’s Dolby Digital, I want Dolby Digital to arrive at the Denon.

(1) What are the essential settings on the Server to make sure it’s not degrading or converting the file?

(2) What are the essential settings on the iOS player to make sure it’s not degrading or converting the file?

(3) What are the essential settings on the tvOS player to make sure it’s not degrading or converting the file?

(4) What are the essential settings on the Amazon Fire player to make sure it’s not degrading or converting the file?

Thanks.

I guess I should add that I’m using Plex only to play local media on my LAN, not for any remote access or streaming from the internet.

[FordGuy61]

For movies and TV shows, Plex picks the first audio track that matches your language settings.

If the client can direct play the audio, it does so.

If it cannot, it will transcode the audio to a supported format.

Example: TrueHD audio in a movie.

AppleTV: Plex will direct play the audio. The AppleTV will convert TrueHD to PCM and then pass it to the Denon (Apple does not permit TrueHD passthrough).

Amazon Fire Stick: Amazon does not support TrueHD audio on their devices. TrueHD will be transcoded by Plex Media Server. It will be passed to the attached device as Dolby Digital, Dolby Digital Plus, or PCM, depending on the FireStick settings, Plex app settings, and capabilities of the TV/receiver/etc to which it is attached.