15
than optimum, causes more output current to
flow, which results in extra heat being gener-
ated in the power output stage. This increase
in temperature will result in a reduced life
expectancy for the amplifier.
The special Balanced Dual Core Auto-
former creates an ideal match between the
power amplifier output stage and the loud-
speaker. A McIntosh amplifier with an Au-
toformer can be used to safely drive multiple
speakers without reducing the life expectancy
of the power amplifier. Refer to figure 17.
There is absolutely no performance limita-
tion with an Autoformer. Its frequency re-
sponse exceeds that of the output circuit itself,
and extends well beyond the audible range. Its
distortion level is so low it is virtually impos-
sible to measure.
Technical Description
ThermalTrak
DC BIAS
OUTPUT
MUTE
THERMAL
SENSORS
BALANCED
AMP
POWER GUARD
ATTENUATOR
INPUT MODE
SWITCH
-
AMP
+
AMP
UNBALANCED
OUTPUT
UNBALANCED
INPUT
BALANCED
INPUT
BALANCED
OUTPUT
+
+
-
-
ThermalTrak
DC BIAS
Block Diagram
of the
Power Amplifier
Figu re 14
Figu re 16
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
MC1.25KW contributes to low operating tempera-
tures. More than 2800 square inches of heatsink area
keep the MC1.25KW operating safely with convection
cooling. No fans are needed. Refer to figure 16.
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
loudspeaker requires. In the case of more than one
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
Fig u r e 17
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