Specifications

milliwatts up to 150 watts, the rated power output of
the MC7150; the additional indication to the right of
the 150 watts mark, is 600 watts. While the MC7150
cannot reach this power level continuously it is possible
for short interval peaks to considerably exceed the 150
watts continuous rating.
HOLD
In the HOLD position, the meter needle locks to the
highest power peak in a sequence of peaks. The meter
is driven to maximum power, electronically held there
until a higher peak passes through the amplifier, which
moves the meter needle to a new indication. If no
further peaks are reached the meter needle will very
slowly return to its rest position (decay rate: 6dB per
minute).
POWER
The POWER switch turns the MC7150 ON or OFF.
The switch does not control the power outlet on the
back panel. If you wish to control the AC power from
a preamplifier control center, leave the switch in the ON
position. Be sure the AC cord of the MC7150 is plugged
into the controlled outlets on the rear of the preamplifier
control center.
OFF: In the OFF position the AC power to the
amplifier is turned off.
Power Guard Operation
Mclntosh Exclusive Digital Dynamic Protection Circuit
Improved recordings and recording techniques have
imposed higher power demands on today's amplifiers.
Poorly 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 (clipping signal) also
produces extra heat energy which will damage most
speakers. Mclntosh leadership in engineering has
developed the Power Guard circuit which - (1) dynami-
cally prevents power amplifiers from being overdriven
into hard clipping - (2) assures that the amplifier will
produce its maximum output without increased
distortion - (3) protects your speaker from excessive
heating. Power Guard is a patented Mclntosh design
(U.S. patent #4048573).
The MC7150 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, exceeds an average of 0.3% (equivalent to
0.3% total harmonic distortion) an amber POWER
GUARD indicator illuminates. With any further increase
in distortion the POWER GUARD circuit operates to limit
the amplifier input dynamically so that the amplifier
cannot be overdriven. POWER GUARD eliminates
amplifier output clipping. 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.
Rear Panel Information
LEFT AND RIGHT OUTPUT
For stereo operation, output connections for
impedances of 2, 4 and 8 ohms are provided on secure,
screw type, gold plated terminals.
INPUT
In the stereo mode of operation both input jacks
accept signal.
AC POWER
The MC7150 is rated for 120 volts, 50/60 hertz.
It uses 0.5 amperes when there is no signal output and
up to 7 amperes with both channels delivering rated
power. A 7 ampere fuse protects the MC7150 electri-
cally. The AC power outlet provided for auxiliary
equipment is neither fused nor switched.
Technical Description
The MC7150 is a stereo power amplifier designed
to operate with loudspeakers having a nominal im-
pedance of 2, 4 or 8 ohms.
It features a new circuit design that holds
harmonic distortion far below the amplifiers remarkably
low noise floor. Only by using special spectrum analysis
measuring techniques is the distortion measurable at
all.
DESIGN PHILOSOPHY
The secret to this performance will sound very
simple, but it is more difficult to carry out than it may
seem. The principle used in the design of the MC7150
was to arrange every stage of voltage or current
MclNTOSH LABORATORY INC., 2 CHAMBERS STREET, BINGHAMTON, NEW YORK 13903
MC7150 Product Preview/Page 4