I’m either not understanding your post properly, or…
The Sonos Amp’s Sub output should be connected to the Nobsound’s audio input, as near as I can tell. You state you have it connected to Sub Out of the Nobsound, which is what I think the Sub should be connected to, not the Sonos Amp.
Essentially, Sonos Amp Sub out to Nobsound Audio input.
Then Nobsound’s Sub Out gets connected to your Sub (but I don’t seem to be able to find images to tell me how it gets connected to the Sub).
Your Sonance speakers get connected to the Sonos speaker posts, ignoring the Nobsound.
There are likely settings on the Nobsound that I’m not familiar with to make it a Sub only device, check its manual.
Hey bruce
So after messing around for an hour I found this
Sonos amp sub out needs to be plugged into the red and white audio in RCA ports on the back of the Nobsound amplifier and it works fine
I had a single RCA male to male going from sub out on the Nobsound amplifier to sub in on the Sonos amp and that’s not how it works.
Well, I’m glad you figured it out.