How do I rename an AirPlay device in Audio MIDI Setup on Mac?

This is more an oddity or annoyance than a problem hampering functionality and I'm sure it was caused by Spotify originally but I can't get rid of it. I was testing playing Spotify from my iPhone to a streamer/amplifier stereo set up. Afterwards, when I opened Spotify on my iMac and tried to connect to the streamer via Airplay, I went to select the device to play through and the amplifier icon appeared but with the name iPhone. This occurs even when my iPhone is switched off, and when I select the amplifier icon named iPhone the system plays perfectly. That is now permanent, I can't seem to do anything to change or delete the name or the icon. And it's not just occurring within the Spotify app. I checked in the Audio Midi Setup and the choice of Airplay devices includes 'iPhone' referring to the amplifier not the phone and there's no way I can find to change it to the amplifier name (NAD M10 v.2). The only suggestion I've come across is to delete the Spotify app and start again, but since the incorrect name is embedded in the Audio Midi Setup options I assume that I actually need to rename the relevant option. Is there any way I can do this? Any thoughts appreciated.

[Re-Titled by Moderator]