Two Notes VB-101 - Manual (Page 14)

Warning regarding the proper use of a loadbox with a tube amplifier
2 What output volume for my amplifier ?
The correct use of your amplifier with a loadbox requires some precautions. Because of the silence
maintained while you are playing, it is much easier to accidentally run your amplifier beyond the
reasonable limits set by the manufacturer than when you are using a speaker cabinet. This can lead
to faster tube wear and, in some cases, more serious inconveniences.
During the first tests at high volume on the amplifier, monitor the color
of the tubes and the general state of the amplifier. Tubes glowing red
or any appearance of smoke are signs of a problem that may lead to
partial or complete destruction of the amplifier.
Keep in mind that the "sweet spot" — the perfect running point of the amplifier, the one that will
give you the tone you’re looking for — is rarely obtained at maximum volume. Furthermore, the
volume control of the amplifier is usually logarithmic, which means that the volume goes up quickly
on the first half of the potentiometer rotation, reaches its maximum at 12 o’clock, and will not change
much beyond that point. Therefore, you can reach the maximum volume of your amplifier even if
the volume potentiometer is not set at maximum.
When reaching the maximum output power of your amplifier, you will hear a lot of distortion,
which may not sound as good as you could hope. Actually, most amplifiers sound rather bad a
maximum volume. Always keep in mind that your amplifier may not have been conceived to be
used at maximum volume for a long stretch of time. Running an amplifier at high volume will cause
premature wear of the tubes and possible malfunctions or damages at the output stage.
The fact that the volume control of your amplifier is not set at maximum
does not mean your amplifier is not running at maximum volume. A
good habit is to keep the usual volume setup you would use in re-
hearsal or on stage, rather than just following what the volume poten-
tiometer indicates.
14 Two Notes Audio Engineering Torpedo VB-101