Revox Re:source MK3 - Manual (Page 19)

5.1 Decoder Module 3 Re:source
18
3 None
The setting None deactivates the
speaker output. There is no
signal at the output available.
This setting is selected if you
want to work without this
speaker. This setting is only
available for the Center and rear
surround speakers.
Speakers with
the setting None
do not appear in
the amplifier
menu. In the
above example, the Center is
deactivated.