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19
Technical Description, con’t
but the inaudible
ultrasonic dis-
tortion is also
undesirable,
since it can
damage valuable
Loudspeaker
System tweet-
ers. You will
never experi-
ence the harsh
and damaging
distortion due to
clipping.
The Power
Guard circuit is
a waveform
comparator, monitoring both the input and output wave-
forms. Under normal operating conditions, there are no dif-
ferences between the shape of these waveforms. If an am-
plifier channel is overdriven, there will be a difference be-
tween the two signal waveforms. When the difference ex-
ceeds 0.3% (equivalent to 0.3% harmonic distortion), the
Power Guard activates the PG light and a dynamic elec-
tronic attenuator at the amplifier input reduces the input
volume just enough to prevent any further increase in dis-
tortion. The Power Guard circuit acts so fast that there are
absolutely no audible side effects and the sonic purity of
the music reproduction is perfectly preserved. The MC207
Power Amplifier with Power Guard is not limited to just
the rated power output, but will actually produce distortion
free output well above its rated power due to the McIntosh
philosophy of conservative design.
Figure 20
With Power Guard
Power Supply Circuits
To compliment the design of the MC207, there is a high
current power supply for the seven power amplifier chan-
nels. Refer to figure 21. The very large Power Transfomer,
has toroidal windings on a toroidal core and can supply
over 35 amps of continuous current. Refer to figure 22
(golf ball is for size comparsion). It is enclosed in the leg-
endary McIntosh Potted Enclosures and weighs over
12.06kg. The super size main filter capacitors can store
over 430 Joules of energy for the seven amplifier channels,
necessary for the wide dynamic range that “Digital Audio”
demands. Refer to figure 23. The power amplifier draws
high current from the AC power line. Therefore, it is im-
portant that they plug directly into the wall outlet.
Also, most owners desire one power switch for the
whole audio system. The MC207 is equipped with a circuit
that provides remote Power Control from a McIntosh A/V
Figure 21
Block Diagram
of the
Power Supply
Figure 22