BHK Preamp Remote Buttons

New BHK preamp. Remote control questions.
There are two On buttons, top left by Off and above In4. What is the difference between them? I know the manual says one is Display and Standby and says preamp only on the lower one, but I would like detailed information on what they do and how they differ.
Top left off button manual says Display and Standby. If I want the preamp to stay on, but keep the tubes off, what do I do? Please be detailed in steps and sequence.
Does the Off button turn everything off completely, or is there still a little juice running through the preamp?
Why is it necessary to press the mute , button above Preamp volume control, before every change of input? If i do not, i get a loud impulse or click noise from my speakers. Is this normal? If not, how can i stop this from happening?
Thanks for your help

The two off buttons are redundant. They should do the same thing. If you want the pre to remain on but the display to be off, hit the dim button. There is no way for the pre to remain on but have the tubes off. When you put the pre in standby, you won’t get any sound and shuts the tubes off. It does keep a portion of the SS circuitry on in order for the warm up period to be shorter. I notice a little click through my my speakers as well when changing the inputs, but it shouldn’t be loud. If you’re running single ended to your amp, it will be marginally louder. I run balanced.