6
1� METER Control Knob
output.
• WATTS - the meter responds to all output.
• HOLD - the dual meter needles will hold the
highest peak until a higher peak is reached.
If no higher peak is reached, the needles will
lower their levels at a rate of approximately
6dB per minute.
Note: When in the WATTS or HOLD position, the meter
and tube lights will be powered On or Off by a
preamplifier or A/V control center connected by a
power control cable if that unit has power control
capabilities.
2� Dual Power Output Meter
Shows both the vacuum tube and solid state
scale is displayed on the top and indicated by
the longer needle. The solid state scale is on the
bottom and indicated by the shorter needle.
3� Standby LED
Indicates that the MC451 is connected to AC
power and ready to be turned on via the front
panel knob or rear panel power control.
In the unlikely event of a fault in the MC451’s
control knob to OFF, wait one minute, then turn
-
ues to occur, the MC451 should be serviced.
4� POWER GUARD SGS
®
(Screen Grid Sensor)
LED
vacuum tube warm up.
current in the KT88 output vacuum tubes. If the
attenuates the input signal in real time to keep
the vacuum tubes operating at safe levels.
5� POWER GUARD
®
LED
over temperature.
time, then makes unobtrusive adjustments to
prevent distortion and potential speaker damage.
6� POWER Control Knob
regardless of any power control connection.
• REMOTE- the MC451 can be powered on
center connected by a power control cable.
• ON- the MC451 will be powered on
regardless of any power control connection.
7� Vacuum Tube Input Stage
Sentry Monitor™ provides protection by
monitoring current in the output transformer.
In the event of a large impedance mismatch,
a short circuit at the output terminals or tube
failure, Sentry Monitor will activate to prevent
potentially destructive levels of current from
When Sentry Monitor is activated, the MC451
To reset the Sentry Monitor protection circuitry,
to ON. If Sentry Monitor continues to engage,
8� Vacuum Tube Output Stage
Note: Because of the high voltage involved with all vacuum
tubes, they should only be replaced by an authorized
McIntosh dealer or service agency.
Front Panel Displays and Knobs