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14
Figure 18
Input Test Signal
The special Balanced Winding Autoformer creates an
ideal match between the power amplifier output stage and
the loudspeaker. A McIntosh amplifier with an Autoformer
can be used to safely drive multiple speakers without re-
ducing the life expectancy of the power amplifier. Refer to
figure 15.
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 your valuable loudspeakers. The
unequaled expertise of McIntosh in the design and manu-
facturing of Autoformers is legendary in the high fidelity
industry. McIntosh engineers know how to do it right.
Power Output Meter
The McIntosh MC501 has a Output Watt Meter that re-
sponds 95% full scale to a single cycle tone burst at 2kHz.
Refer to figure 16. Voltage and current output are electroni-
cally 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 MC501 incorporates a version of the McIntosh Sentry
Monitor Output Transistor Protection Circuit. Refer to Fig-
ure 17. There is absolutely no compromise in sonic perfor-
mance with this
circuit, and it en-
sures safe opera-
tion of the ampli-
fier under even the
most extreme oper-
ating conditions.
The different types
of protection cir-
cuits incorporated
in the MC501 in-
sure a long and
safe operating life.
This is just one of
the many characteristics of McIntosh Power Amplifiers
that make them world famous.
The MC501 also includes the unique patented McIntosh
Power Guard circuit.
Power Guard eliminates
the possibility of ever
overdriving the amplifier
into clipping. Refer to
figures 18, 19 and 20. An
overdriven amplifier can
produce both audible and
inaudible distortion levels
exceeding 40%. The au-
dible distortion is un-
pleasant to hear, but the
inaudible ultrasonic dis-
tortion is also undesir-
Figure 17
Figure 16
Figure 15