I came across a page with some info about how to use the Standby switch on tube amps and thought I'd share it with you.

Here is the link to the page: http://www.musictoyz.com/gearhead/gear14.php

Quoting...

"My advice for long tube life in amplifiers with a STANDBY switch: When first turning on the amplifier,

1. Place the STANDBY switch in the OFF position.

2. Switch the POWER switch ON.

3. Wait at least one minute before moving the STANDBY switch to the ON position.

Turn off the amplifier with the POWER switch leaving the STANDBY switch in the ON position. This bleeds the high voltage within the amplifier. With the next start up, repeat the procedure described above."

I found this pretty useful, especially the last part about how to turn off the amp because usually I come across instructions on how to turn ON a tube amp but not how to turn OFF the tube amp.
For example, it seems I personally was doing it wrong. If I understood the info above correctly, when one is turning off a tube amp, one should leave the Standby switch ON. I used to turn the Standby switch OFF before turning off the amplifier.

Maybe that's why I ended up with the sound on my amp coming and going and what seems to be a weaker sound. I guess we never stop learning new things!