To power the amplifier on press the red Power button. The Mute LED will start blinking red and the Power
LED will light blue, indicating that the amplifier is going through the power on cycle. The Mode LED will
indicate the last used mode: green for Tetrode mode and red for Triode mode.
During standby mode the user can also change tetrode triode mode by pressing the mode button once to toggle
between modes, and the Mode LED will change between red and green to indicate the mode that the amplifier
will power up in.
The power on cycle takes about 30 to 45 seconds. During this time the deck LEDs next to the output tubes
blink about 20 seconds into the power on cycle, indicating that the auto bias system is adjusting the bias voltage
of the output tubes. The top deck LEDs will each stabilize in turn indicating that the output tubes have reached
their operating points, which is required before the Mute relay is released to allow signal.
If at any time during this sequence the Power LED turns off and the Mute LED flashes fast red then there is a
fault, either Red Tube or Power. See the Fault section.
When the Power on cycle is completed the Mute LED turns off and the Power and Mode LEDs remain on.
If there are any low tubes that cannot be biased the Mute LED will blink slow green, but the amplifier will still
operate.
The amplifier is now ready to play music.
Mute and Unmute
While the amp is powered on, the user can mute the amplifier by pressing the Mute button on the front panel or
applying a signal to the Mute Trigger. The Mute LED turns solid red and the amplifier’s input is muted. The
deck LEDs next to the output tubes are turned off while the amplifier is in mute.
To unmute the amplifier, press the Mute button again, and the Mute LED will blink red to indicate that the amp
is unmuting. The deck LEDs will all blink to indicate that the tubes are being biased. When the unmute cycle is
completed and the tubes are all at their operating points, the Mute LED is turned off. The deck LEDs are
steady if no music is playing, with occasional flickers as the output tube bias is adjusted.
MB-450 Series III Signature Monoblock Owner’s Manual
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