McIntosh MC 7270, Руководство пользователя

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THE MclNTOSH (EXCLUSIVE) POWER GUARD
DIGITAL DYNAMICS PROTECTION CIRCUIT
Improved recordings and recording techniques have im-
posed higher power demands on today's amplifiers. Poor-
ly designed amplifiers can present music listeners with a
form of harsh unpleasant distortion due to amplifier
overload (hard clipping). Clipping, which looks and acts
like non musical square waves, is caused when the
amplifier is asked to produce more power output with
low distortion than it is capable of or designed to deliver.
Amplifiers, when driven to clipping, can deliver up to 40%
harmonic and intermodulation distortion that decreases
the pleasure and enjoyment you get from listening. This
form of distortion (clipped signal) also produces extra heat
energy which will damage most speakers. Mclntosh
leadership in engineering has developed the Power Guard
circuit which - (1) dynamically prevents power amplifiers
from being overdriven into hard clipping - (2) assures that
the amplifier will produce its maximum output without in-
creased distortion - (3) protects your speaker from ex-
cessive heating. Power Guard is a patented Mclntosh
design (U.S. patent #4048573).
The MC 7270 has a circuit that compares the wave
shape of the output signal to the input signal. If the
disparity between the two signals, due to overdrive, ex-
ceeds an average of 0.3% (equivalent to 0.3% total har-
monic distortion) an amber POWER GUARD indicator il-
luminates. With any further increase in distortion the
POWER GUARD circuit operates to limit the amplifier in-
put dynamically so that the amplifier cannot be over-
driven. POWER GUARD eliminates amplifier output clip-
ping. POWER GUARD only operates when the amplifier is
asked to deliver more power than that for which it was
designed. While the power output remains within these
limits the POWER GUARD indicators do not illuminate.
12 FRONT PANEL CONTROLS