McIntosh MC301 Owner's Manual page 15

conditions with the benefits of lower distortion and
cooler operation. Precision metal film resistors and
low dielectric absorption film capacitors are used in
all critical circuit locations.
The output signals of the two balanced circuits
are coupled together in the unique McIntosh MC301
Output Autoformer. It provides low distortion power
transfer at frequencies from below 20Hz to well
beyond 20,000Hz with optimum impedance points of
two ohms, four ohms and eight ohms. The unequaled
expertise of McIntosh in the design and manufactur-
ing of autoformers is legendary in the high fidelity
industry.
The high efficiency circuit design of the MC301
contributes to low operating temperatures. More than
800 square inches of heat sink area keep the MC301
operating safely with convection cooling.
UNBALANCED
INPUT
UNBALANCED
OUTPUT
+
AMP
INPUT MODE
POWER GUARD BALANCED
SWITCH
ATTENUATOR
AMP
-
AMP
+
BALANCED
INPUT
-
+
BALANCED
OUTPUT
-
Block Diagram
of the
Power Amplifier
are needed. Refer to figure 17.
Autoformers
All solid state power amplifier output circuits work
best into what is called an optimum load. This op-
timum load may vary considerably from what a
No fans loudspeaker requires. In the case of more than one
ThermalTrak
DC BIAS
THERMAL
SENSORS
MUTE
ThermalTrak
DC BIAS
Figure 15
Figure 17
Technical Description
loudspeaker connected in parallel, the load to the
power amplifier may drop to two ohms or even less. A
power amplifier connected to a load that is lower than
optimum, causes more output current to flow, which
results in extra heat being generated in the power out-
put stage. This increase in temperature will result in a
reduced life expectancy for the amplifier.
The special Balanced Winding Autoformer creates
an ideal match between
the power amplifier
output stage and the
loudspeaker. Refer to
figure 18.
There is absolutely
no performance limi-
tation with an Auto-
former. Its frequency re-
sponse exceeds
that of the out-
put circuit itself,
and extends well
beyond the au-
dible range. Its
distortion level
is so low it is
OUTPUT
virtually impos-
sible to measure.
In the rare event of a power amplifier out-
put circuit failure, the McIntosh Autoformer
provides absolute protection from possible
damage to your valuable loudspeakers. The
unequaled expertise of McIntosh in the design
and manufacturing of Autoformers is legend-
ary in the high fidelity industry. McIntosh
engineers know how to do it right.
Figure 18
15