When faceplate has a Stby switch hole I always install the switch. I improve it installing a resistor over its contacts and when Mains is switched On there begin to flow low HV current and elecgrolyts pre-charge slightly and this depends of resistor value. Tube cathodes don't "poison" so switch comes true Standby Amp can be played as well but sound is quiet and very distorted. Obviously that Stby switch resistor could be used as a "bedroom brown sound effect" when its value is select so that current floaw comes higher?Ok, gotcha. I don’t put standby switches in my amps anymore after learning what KF points out. I’m not sure how the MV would handle being close to the power switch and/or pilot light. I guess it depends on the light but it may be susceptible to more hum there.
When amp does not have a stby switch tubes can produce so bad sounds first minute or so that possibly there is a danger to destroy the loudspeaker but work just fine when they have reach operation temperature. I have been challenged speaking against "Leo" what comes "grounding" but what comes to Stby I think he was right!!! Yes I understand that indirect/delayed heating rectifier tubes were designed but still direct heating rectifiers are often favored and they and stby switches belong to the same phase in tube technology.