Here's some interesting reading on standby switches from a well known amp expert who also is a contributor to this forum. If you only buy one book on preamps, this is THE one.
The Valve Wizard The case can be made that they actually do more harm than good when wired in the usual way.
There is another contributor to this forum who has written a very good series of books that agrees with this as well. Standby Switches
The Valve Wizard The case can be made that they actually do more harm than good when wired in the usual way.
There is another contributor to this forum who has written a very good series of books that agrees with this as well. Standby Switches