Exactly the same problem as mentioned in the ‘Port Line-Out very low volume’ topic but alas unanswered there - there appears to be confusion between using the Port to drive the HiFi or the Hifi to feed into Sonos… I guess the latter is more common, and I am unusual (but not unique) in using Sonos to drive the HiFi.
I have a TEAC series 300 component HiFi and a Play:5 in the same room. If I group both to expand the sound stage (not exactly surround sound but...) there is a great disparity between the Sonos Setting for the Play and the (much greater) volume setting for the Port. The HiFi volume is set to a normal listening level for the other Hifi components - CD, cassette, DAB, and switching between them requires no volume adjustment. Switching to Sonos requires either the the Port Sonos volume to be set near max, or the HiFi volume greatly increased, which causes consternation if you switch to another source without readjusting… Also if you increase the group volume, the Play volume overtakes the Port/Hifi volume fairly swiftly, necessitating more adjustment. (the volumes increase disproportionally). If the HiFi volume is set to ‘normal’ the Sonos Port volume maxes out swiftly and the HiFi is drowned out by the Play:5 with its additional volume headroom/freeboard.
The Port has an input sensitivity adjustment. Why can it not have a similar output matching adjustment to augment or attentuate?
It looks like the only option that I have is to fit an additional preamplifier between the Port and the aux input on the HiFi to augment the Port output to match that of the other HifI components (2V RMS apparently). The expensive work around I had with my old Connect was to use a matching TEAC DAC whose output was on a par with the rest of my TEAC Series 300 components. Alas the Port does not have the digital output that I used… The Connect is now obsolete for S2 purposes and has been upgraded to the Port.