Balanced Audio Technology VK-5 Owner's Manual - page 7
Mute function:
The VK-5 has two mute modes: manual and automatic. Putting the Mute switch in Mute
position will always override the automatic function and disable the outputs.
When the unit is powered up it automatically self-mutes until the proper operating points of
the circuitry are reached. It will then automatically go into Play mode, provided the Mute
switch is in the Play position.
Changing the power switch position from On to either Off or Sleep even for short time, will
make the unit reset its power sequencing circuit and mute its output. It will then require
about 45 seconds for the unit to become operational again.
The mute function is coupled to a low line voltage sensor. When line voltage drops below an
allowable value (for example during a brown-out condition) the unit will automatically mute
and remove the plate voltages from gain stages. Once the line voltage recovers to a normal
level, the VK-5 will resume its operation.
If the line voltage is insufficient for normal operation during turn-On, the unit will not
proceed beyond Sleep mode until the line voltage reaches a proper level.
Overcurrent Protection:
Both channels in the VK-5 are protected from certain overload conditions via electronic
current-sensing circuits. If an overcorrect condition is detected in either channel (for
example, a short in one of the regulator tubes), the unit will immediately be disabled, its high
voltage supplies disconnected and the output muted. The protection circuit may be reset by
turning the unit Off for a short period of time. However, if the fault condition remains, the
unit will again be disabled and therefore require professional service.