Can I use Avantree TV Headphones / Transmitters while using my 5.1 / Dolby / 7.1 Surround Sound system?

To use your 5.1 Surround Sound system at the same time, all you need to do is to get the Avantree Orbit as a Bluetooth transmitter, taking advantage of its passthrough function as well as the Surround Sound support

If you want to achieve 7.1 Surround Soundand you have an AV Receiver with HDMI Zone 2 output, then you need to add an extra HDMI Audio Extractor to extract the optical audio signal for the TV headphone / Transmitter.

Here is the diagram of the reference connections:

RCA Zone 2 on AVR is not recommended because it normally cannot be in sync with the main zone.