16
(equivalent to 0.3% harmonic 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 au-
dible side effects and the sonic purity of the music repro-
duction is perfectly preserved. The MC202 Power Ampli-
fier 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 MC202, there is a high
voltage power supply for both channels. Refer to figure 19.
The power amplifiers draw high current from the AC
power line. Therefore, it is important that they plug directly
into the wall outlet.
Also, most owners desire that there be one power
switch for the whole audio system. The MC202 is equipped
with a circuit that provides remote Power Control from
your McIntosh Preamplifier or Control Center. When you
turn on your preamplifier a digital 1 (+5V) signal oper-
ates the power relay in the MC202. The MC202 also has a
remote Power Control Out Jack. The Power Control signal
from this jack is delayed by a fraction of a second so that
the turn on power surge of the next power amplifier occurs
at a later time. This helps prevent power circuit overload
that could trip circuit breakers or blow fuses, a very impor-
tant feature in a high power Home Theater System employ-
ing three MC202 Power Amplifiers.
The MC202 can provide greater than 50 amperes peak
output current to drive uneven speaker loads. Some poor
speaker designs have input impedance that dip to 1 or 2
ohms at various frequencies and the MC202 has the output
current reserve to drive them. The MC202 has main filter
capacitors that guarantee an excellent signal to noise ratio
and the energy storage necessary for the wide dynamic
range that Digital Audio demands.
Figure 19
Block Diagram of the Power Supply
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