3G Audio Differences
Dolby Digital Encoding
The Just Add Power 3G 718AVP and 749AVP accept Dolby Digital inputs via HDMI.
They then convert the signal into stereo-encoded Dobly PLII. This allows you to get 2 channel analog audio, 5.1 audio on an AVR and 2 channel on a TV that is using its built in speakers.
Atmos - Lossless Encoding
The Just Add Power 707POE, 747POE, 717HIFI transmitters can encode and pass along lossless audio formats. They do not break out analog audio.
Dolby Digital Decoding
Both 3G 518AVP and 508POE can decode and output the Dobly PLII converted 5.1 as well as 2 channel audio. It is up to the AVR to decode the PLII back into 5.1 audio.
Atmos - Lossless Decoding
To get ATMOS you must be using a the 707POE, 717HIFI or 747POE Transmitter. The 508POE and 518AVP can both output ATMOS. They do not decode it but pass it through.
2 Channel Analog Audio
The 718AVP & 749AVP Transmitters as well as the 518AVP Receiver all have a 3.5mm analog audio with volume and lipsync correction.