13
Illuminating Color from Green to Blue. Refer to figure
12.
Input Switch
The Input Mode Switch, which is located on the Rear
Panel of the MC2152, allows selec-
tion of either the Balanced or Unbal-
anced Input. Refer to figure 13.
Auto Off Switch
The MC2152 incorporates Power Save Circuitry to
automatically place the MC2152 into the power saving
Standby Mode approximately 30 minutes after there
has been an absence of an audio input signal.
When there is a Power Control Connection be-
tween the MC2152 and a Preamplifier with Power
Save Circuitry, the AUTO OFF
Switch is bypassed (located on the
Rear Panel of the MC2152). Refer
to figure 14.
In the event there is no Power Control Connection
and the Power Save Circuitry is activating inappropri-
ately relative to your specific use of the MC2152, place
the AUTO OFF Switch in the DISABLE position.
Note: If the Power Save Circuitry has switched Power
to the MC2152 OFF, place the POWER in the
OFF Position and then in the ON position to
reset the circuitry.
Sentry Monitor
The MC2152 Sentry Monitor Tube Protection Circuit-
ry provides protection to the Power Amplifier in the
event of an impedance mismatch between the MC2152
and the Loudspeaker(s). It will also activate if there is
a short circuit at the MC2152 Output Terminals (or the
Loudspeaker Terminals) or if a MC2152 Power Output
How to Operate
How to Operate
Power Control
The POWER CONTROL is located on the Front Panel
of the MC2152, set the Control to
the REMOTE Position. Refer to fig-
ure 10. The MC2152 Power Ampli-
fier will turn ON or OFF as the Pre-
amplifier its is connected to (via the
Power Control Connection) turns
On or Off . For manual operation, place the POWER
CONTROL to the ON Position as desired. The LED
indicator located on the Front Panel below the “Mc-
Intosh” Name is illuminated
when the MC2152 is connected
to an active AC Outlet. Refer to
figure 11.
Note: When the MC2152 is first switched On, there is a
Warm-Up period of time during which no sound
will be heard. There is also sequential illumina-
tion (amber color) of the Small Signal Vacuum
Tubes. After the Warm-Up period of time, sound
will be heard and the illumination color of the
Small Signal Vacuum Tubes will change to either
Green or Blue as were previously selected. The
Illumination of Small Signal Vacuum Tubes can
also be switched OFF, by placing the TUBE
LIGHT Control in the OFF position.
Tube Lights Control
The eight Small Signal Vacuum Tubes are Illuminated
by LEDs to indicate the various Operation Modes
of the MC2152 Power Amplifier.
Refer to the Left and Right Channel
Charts located on page 12. When
the MC2152 Power Amplifier is in
the Normal Mode of Operation, the
default LED Illuminating Color is
Green in color. Rotating the TUBE
LIGHTS CONTROL clockwise will change the LED
Notes: 1. The impedance of a Loudspeaker actually varies as
the Loudspeaker reproduces different frequencies.
As a result, the nominal impedance rating of the
Loudspeaker (usually measured at a midrange fre-
quency) might not always agree with the impedance
of the Loudspeaker at low frequencies where the
greatest amount of power is required. Contact the
Loudspeaker Manufacturer for additional informa-
tion about the actual impedance of the Loudspeaker
before connecting it to the McIntosh MC2152.
2. When the given channel doesn’t return to Normal
Operating after the Power Switch has been switched
back ON, then place the Power Switch in the OFF
position and disconnect the AC Power Cord from
the MC2152. Then contact your McIntosh Dealer for
repair of the Power Ampifier.
Figure 10
Figure 11
Figure 12
Figure 13
RIGHT OUTPUTS
8
Ω
+
4
Ω
+
2
Ω
+
COM
-
LEFT OUTPUTS
COM
-
2
Ω
+
4
Ω
+
8
Ω
+
CLASS 2 WIRING
RIGHT OUTPUTS
8
Ω
+
4
Ω
+
2
Ω
+
COM
-
LEFT OUTPUTS
COM
-
2
Ω
+
4
Ω
+
8
Ω
+
CLASS 2 WIRING
Figure 14
Tube should fail. During normal operation the Sentry
Monitor Tube Protection Circuitry has no effect on the
performance of the Power Amplifier.
In the event a problem occurs, the circuitry will
activate to prevent potentially destructive high levels
of current from flowing in the amplifier. The illu-
mination color of the Small Signal Vacuum Tubes of
the affected channel will change from Green or Blue
to Red. To reset the Sentry Monitor Tube Protection
Circuitry first note the position of the POWER Switch.
If the POWER Switch is set to the REMOTE position,
switch Off the Preamplifier for approximately one
minute and then switch the Preamplifier On. When
the POWER Switch set to the ON position, place the
POWER Switch to the OFF position for approximately
one minute, then place the POWER Switch to the ON
position.
