21
Autoformer
All solid state power amplifier output circuits work best
into what is called an optimum load. This optimum 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 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 re-
duced life expectancy for the amplifier.
The special Balanced Dual “C” Core Autoformer creates
an ideal match between the power amplifier output stage
and the loudspeaker. Refer to figure 20. A McIntosh ampli-
fier with an Autoformer can be used to safely drive multiple
speakers without reducing the life expectancy of the power
amplifier.
There is absolutely no performance limitation with an
Autoformer. Its frequency response exceeds that of the out-
put circuit itself, and extends well beyond the audible range.
Its distortion level is so low it is virtually impossible to
measure.
In the rare event of a power amplifier output circuit fail-
ure, the McIntosh Autoformer provides absolute protection
from possible damage to valuable loudspeakers. The un-
equaled expertise of McIntosh in the design and manufac-
turing of Autoformers is legendary in the high fidelity indus-
try. McIntosh Engineers know how to do it right.
Power Output Meter
The McIntosh MC2KW Power Amplifier has a huge hand
built Output Watt Meter that responds 95% full scale to a
single cycle tone burst at 2kHz. Refer to figure 21. Voltage
and current output are electronically measured, multiplied
and fed to a special circuit that accelerates the pointer
movement in the upward direction. When the pointer
reaches its peak it pauses only long enough for the human
eye to perceive its position, then drops. It is almost 10 times
faster than a professional VU meter.
A front panel switch is provided to change the meter to
the Watts Hold Mode of operation. This allows fast upward
movement of the pointer but greatly increases Hold Time at
the peak of its travel. The highest power output of the
source material is thus recorded.
Protection Circuits
The MC2KW Power Amplifier incorporates the McIntosh
Sentry Monitor Output Transistor Protection Circuit. Refer
to Figure 22.
There is abso-
lutely no com-
promise in sonic
performance
with this circuit,
and it ensures
safe operation of
the amplifier un-
der even the
most extreme
operating condi-
Figure 20
Figure 21
Figure 22
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