With optical audio output missing in the ATV4, I noticed audio quality not quite as good as ATV3's direct optical output to my stereo receiver. Especially true when listening to iTunes music. Now have optical input coming from the TV where ATV4 is connected. Tweaking some of the ATV4 audio settings seems to have brought it back to about the same level as ATV3. This included surround sound set to stereo instead of auto, turning off sound effects, set audio mode to 16 bit, and turning Siri off. Some of this may not have done anything, but I wanted to remove as much ATV interference as possible in keeping the audio signal unaffected. Anyone else notice this or try any audio tweaking? Granted, my system is not surround sound but only stereo.