You spent $500 on a soundbar or $2,000 on a surround sound system, and Plex is sending it stereo PCM. The movie has Dolby Atmos on the file, but your receiver shows “2.0 PCM.” This is one of the most common Plex frustrations — and it’s almost always a configuration problem, not a hardware limitation.
What Audio Passthrough Actually Means
Audio passthrough means Plex sends the original audio stream — bit-for-bit, untouched — directly to your AV receiver or soundbar for decoding. No transcoding on the server, no conversion to a simpler format, no quality loss. Your receiver does the decoding, which is exactly what it was built to do.
Without passthrough, Plex transcodes the audio to stereo PCM or a lower-quality format before sending it. You lose spatial channels, object-based audio (Atmos), and dynamic range. The difference between Atmos passthrough and stereo PCM on a capable system is night and day.
Audio Formats: What Each One Needs
- AAC / MP3 (2.0): Always works. No passthrough needed — it’s already simple stereo
- AC3 / Dolby Digital (5.1): Supported by virtually every device. Passthrough works on HDMI, optical, and ARC
- E-AC3 / Dolby Digital Plus (7.1): Requires HDMI. Optical doesn’t have the bandwidth. Most smart TVs and streaming sticks support this
- DTS (5.1): Widely supported on receivers. Some TV apps (LG, Samsung) don’t pass DTS — they transcode to PCM
- DTS-HD MA (7.1): Lossless. Requires HDMI direct to a receiver. No TV app or streaming stick supports this — only dedicated players (Shield, Apple TV 4K with eARC)
- TrueHD (7.1): Dolby’s lossless format. Same requirements as DTS-HD MA: HDMI direct to receiver
- TrueHD + Atmos: Object-based audio layered on top of TrueHD. Requires HDMI 2.1 or eARC to receiver. NVIDIA Shield Pro is the gold standard client for this
Client-Side Settings
The client is where most passthrough problems live. In Plex player settings:
- Audio output: Set to “HDMI” or “Receiver” (not “Speakers” or “TV”)
- Allow Passthrough: ON
- Passthrough codec toggles: Enable AC3, DTS, EAC3, and TrueHD individually — only enable what your receiver actually supports
- Audio quality: Set to “Original” or the highest available bitrate
On NVIDIA Shield: Settings → Device Preferences → Sound → Advanced → Surround Sound = “Auto” (not “Always” or “Never”).
On Apple TV 4K: Settings → Video and Audio → Audio Format = “Change Format” + select Dolby Atmos. This also requires eARC from TV to receiver or direct HDMI to receiver.
Server-Side Settings
On the Plex server, the key settings are:
- Under Settings → Transcoder: Don’t limit audio streams. Leave “Background audio” disabled unless you specifically want stereo fallback tracks
- Under Settings → Library: Make sure audio tracks aren’t being excluded or deprioritized by the scanner
- In the movie/show detail page: Check the audio track order. If a stereo commentary track is listed first, Plex will select it by default. Manually set the default audio track to the surround track
The HDMI Chain Problem
Audio passthrough can break at any point in the HDMI chain:
- Player → TV → ARC to receiver: ARC only supports DD/DD+ (lossy). You need eARC (HDMI 2.1) for TrueHD/Atmos/DTS-HD. Check your TV specs — many “HDMI 2.1” TVs only have eARC on port 1
- Player → Receiver → TV: This is the best chain for lossless audio. The receiver decodes everything; the TV just displays video
- Old HDMI cables: A cable that can’t handle 48Gbps (HDMI 2.1 Ultra High Speed) may silently drop Atmos metadata. Use certified cables
How to Verify Passthrough Is Working
- Play a movie with a known Atmos or DTS-HD track
- Check your receiver’s display — it should show “Dolby TrueHD”, “Atmos”, “DTS-HD MA”, or similar. If it shows “PCM” or “Stereo”, passthrough is not working
- In Plex, check the Now Playing dashboard — if audio shows “direct play”, passthrough is working. If it shows “transcode”, something in the chain is forcing conversion
- Use Tautulli for detailed playback logs — it will show exactly what audio codec is being played and whether it’s being transcoded
When Transcoding Audio Is Actually Fine
Not every situation needs passthrough. If you’re watching on a laptop, phone, or a TV with built-in speakers, stereo PCM is the correct output. Don’t fight passthrough on devices that can’t decode surround sound — let Plex transcode to stereo and save yourself the troubleshooting. Passthrough only matters when you have a receiver or soundbar that can actually decode the format.
How PlexBeam Handles Audio
When PlexBeam offloads video transcoding to a remote GPU, the audio stream is passed through untouched by default. Your client still receives the original Atmos or DTS-HD track — only the video gets transcoded. This means you get the best of both worlds: 4K HDR video transcoded smoothly on a powerful GPU, with lossless audio delivered directly to your receiver.