McIntosh MC207 - Manual (Page 19)

19
Technical Description, con’t
rience 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 differ-
ences between
the shape of
these waveforms. If an amplifier channel is overdriven,
there will be a difference between the two signal waveforms.
When the difference exceeds 0.3% (equivalent to 0.3% har-
monic distortion), the Power Guard activates the PG light
and a dynamic electronic attenuator at the amplifier input
reduces the input volume just enough to prevent any further
increase in distortion. 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 pre-
served. 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.
Power Supply Circuits
To compliment the design of the MC207, there is a high
current power supply for the seven power amplifier chan-
Figure 20
With Power Guard 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 legendary
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 important that they plug di-
rectly 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 Con-
trol Center. When the A/V Control Center is switched On a
digital “1” (+5V) signal operates the power relay in the
MC207. The MC207 also has a remote Power Control in-
Figure 21
Block Diagram
of the
Power Supply
Figure 22