I’m not sure I understand. You can’t control the Port’s own internal volume level using a receiver’s physical control. You’d be controlling the downstream equipment’s amplification, in the conventional way. The Port would be just another input to the receiver. 

Thank you for taking the time to reply. Much appreciated

The Port is connected to a receiver, CD, Phono. I can control the Sonos volume from the internal Sonos volume control slider in the app. Since all the devices feed into the Port through the receiver, i hoped to be able to control the volume of songs using the receiver volume control knob, rather than having to open the app. Your answer suggests what i wish for isn’t possible… is that so? If it is, it is good to know and stop looking for a solution. 

I see that when playing a blue tooth connected mobile device through Sonos one can control the volume with the volume control toggle on the mobile device----hoped it worked that way with volume control on receiver. 

When the Port is a source for your receiver you should be able to change the volume by using the knob on the receiver, just like you would when playing a CD on a CD player. On the Port the volume would be set to fixed.

You state: “The Port is connected to a receiver, CD, Phono.” This is confusing to me. Can you tell us on what port on your receiver the Sonos Port is connected? Can you also explain how you’ve connected the CD and phono to the Port?

Or am I not understanding you right and you want to change the volume for other Sonos devices with the knob on the receiver. That is impossible.

It sounds as though the receiver is before the Port, feeding any of the named sources into the Port’s Line-In? Again, the receiver’s volume control would normally have no effect on a line level output, unless the Port is somehow connected to a ‘preamp out’ on the receiver.

More details of the topology are indeed required. 

Possibly move the Port from the RX’s Line Out to the Pre-Amp Out?

That would put it behind the receiver's volume control.

Not optimum sound as you will be feeding the Port a lower level signal than expected and see increased noise as the Port internals boost the incoming lower level signal back to higher levels. You can fiddle this for the least impact by balancing the RX and Port volume settings but it can be frustrating to do.

Thanks for your replies. He is on camping trip now and will have to look at your suggestions after he returns. :-) 

Sorry for my limited knowledge of the terms you are using. Would the “pre-amp out” be a set of jacks on the back of the receiver or the back of the Port?