It's safe to say that most of the lore around the proper way to turn a tube
amplifier on or off is apocrypha with little basis in practical application. Which
makes sense if you think about it. If tube amplifiers were really such fragile
objects that they require a special procedure to turn them on or off, careless
musicians would be damaging their gear all the time. In practice, musicians
regularly use vintage tube amplifiers that haven't seen any kind of service in
decades that continue to function reliably.
The universal absence of a standby feature on tube hifi gear should be another
clue that such a feature is not strictly necessary for preventing damage to the
amplifier.
Around here, we tend to leave the
STDBY
switch in the up position and only flip it
to the down position when the amp is already on and we want to temporarily
mute its output. This is, in fact, the intended function of the
STDBY
switch.
Can I change the power switch setting while the amp is on?
Yes. This feature is hot switchable.
You might hear a little bit of a pop.
There is no
need to power off the amplifier or engage standby.
Can I unplug or plug in speakers while the amp is on?
When plugging in or unplugging speakers, the amp should be powered off or the
standby should be engaged.
Can I change the output impedance setting while the amp is on?
When adjusting the impedance selector switch, the amp should be powered off or
the standby should be engaged.
What if I plug a speaker cabinet into the AUX output with nothing
attached to MAIN?
The
MAIN
output uses a shorting jack that shorts the amplifier's output when no
speaker is connected in order to prevent damage to the amplifier in the event
that a user mistakenly powers the amplifier on without a speaker connected to
the output. Therefore, if you plug a single speaker cabinet into the
AUX
output
with no speaker attached at the
MAIN
output, the amplifier's output will remain
shorted and little or no signal will reach the connected speaker.
What if I run the amp with no speaker attached?
Generally speaking, it's not a good idea to run a tube amp without an attached
speaker load. This can cause damage to the power amplifier tubes or the output
transformer.
The output transformer is a fairly expensive part that you don't want