A little UP please. ; )

If I use the optical audio out port of my TV, convert the signal to analog and then run the signal over a cat6 cable to finally connect it to my amp with an analog red and white RCA plug, would I loose the 5.1 sound and be stuck with simply a stereo sound?

Thanks,

Another alternative question: if I use a regular HDMI over cat6 balun, and use the HDMI ARC port of my TV, could I use that setup to transfer the sound of my TV to my amp (I would put the transmitter in the back of my TV and the receiver in the back of my amp)? A regular HDMI over cat6 balun would be way cheaper, but would it keep the 5.1 sound parameters?

Thanks!

Yes. You’ll be getting only stereo. 
 

I’ve not answered anything upstream, because you’re trying to do things I’ve never needed to do. I understand the concept, but I’ve never seen HDMI-ARC work across CAT-6 baluns before. I’d be awfully tempted to pull the audio off the stream before it reaches the TV, and ignore the apps on the TV itself. If I needed those apps, I’d run them on a streaming box such as Apple TV, etc. There’s just to many potential failure points if you run the audio from the TV across all those extra connections. 
 

In all honesty, I’d also think that Sonos may not be the ideal solution for you. You seem to want to use a Sonos CONNECT to be part of your home theater solution, but the CONNECT is only a stereo device, and can’t handle a 5.1 signal. If you were trying to use Sonos, I’d suggest rather than using your Onkyo, you go with a Sonos sound bar (there are three choices), a SUB and a pair of Sonos speakers as surrounds. Then the sound bar could be under the TV and directly connected, and the SUB and surround speakers would connect wirelessly.  Then I’d repurpose the Onkyo as a music only solution.

If you’re looking for more advice on dealing with the audio signal from your TV to your Onkyo, there are more generic websites for home theater users that may have more experience to provide you answers. Most users here are Sonos users, and consequently may not have the experience to assist you. 

Hi,

Thanks for the reply.

I understand your point. I'm using Sonos connect to use my HT speakers as Sonos skeapers when not using them as HT surround sound, ie when I only want to listen to Spotify for instance and not watching a movie. When watching a movie and wanting 5.1 sound, I use my Onkyo amp. I also have other pairs of speakers linked to a connect amp for Spotify in other rooms of my house.

Does that make more sense? At least regarding my usage of the Sonos ecosystem?

Thanks,

Then the CONNECT as you have it right now, or the Port, which is the ‘new’ version, is all you need to get he Sonos ecosystem available to your Onkyo. Simply take the analog out from the CONNECT/Port and connect it to your tape in on the Onkyo. Then connect the tape out on the Onkyo to the analog in on the Sonos, and you’re done. Anything playing on the Onkyo will also play on your Sonos, with the normal delay expected on the Sonos line in, and anything playing on the Sonos system will play in sync across both your Sonos speakers and the speakers connected to the Onkyo.

This is a pretty standard setup, used by many Sonos customers. 

Ok, thanks. I do not wish to play the sound from the Onkyo on the Sonos speakers, just the other way around (sound from the Sonos that needs to be played on the Onkyo). This already works. It's more the question of the TV sound being played on the Onkyo that remains. But as suggested, maybe I'm not in the right forum for that. ; )

Thanks

From what I know about those baluns, most don’t have the capability to handle HDMI-ARC, and I suspect your Onkyo can’t handle it either. 

Hi,

Thanks again for the help. My Onkyo amp does handle HDMI ARC, but thanks for the info regarding the baluns. I might try to look for an optical over cat6 baluns. That would keep the 5.1 parameters, right?

Optical carries Dolby Digital just as well as HDMI-ARC. 

Thanks