Specifications

amplification to be as linear as possible.
This linear operation is accomplished by using
several different techniques.
1. Each transistor is selected to have nearly constant
current gain (Beta) over the entire range of currents
at which the transistor must operate.
2. The load impedance presented to each amplification
stage is made to be as uniform as possible for all
signal levels.
3. The input impedance of stages is increased and
linearized where possible by using emitter degener-
ation.
4. Resistors and capacitors in the signal path are
carefully selected to have exceedingly low voltage
coefficients (low change of resistance or reactance
with applied voltage). Precision metal film resistors
and low dielectric absorption film capacitors are
used in all critical circuit locations.
5. Output transistors have matched uniform current
gain, high current gain-bandwidth product, low
output capacitance, and large active-region safe
operating area. These characteristics and the
automatic tracking bias system eliminates cross-
over distortion. The distortion graphs show clearly
that distortion does not increase at low power
output levels.
OVER 58 JOULES OF ENERGY STORAGE
Huge main filter capacitors are used to guarantee
an excellent signal to noise ratio and the energy storage
necessary for the wide dynamic range that "Digital
Audio" demands.
ILLUMINATED, PEAK RESPONDING OUTPUT
WATTMETERS
The MC7150 is the first high fidelity power amplifier
to have REAL OUTPUT WATTMETERS. The power
output in WATTS of any amplifier is determined by
multiplying the output voltage (E) by the output current
(I), El = W. Output meters on other amplifiers are only
voltmeters. Output current is not considered.
Calibration is in watts and is based on the false premise
that all speakers have a fixed impedance regardless of
frequency. In fact, the impedance of many poor
speakers designs varies by as much as 4 to 1. For a
specific output voltage the current varies inversely to
the speaker impedance. So if the speaker impedance
is lower, the output current and power are higher. Since
Mclntosh can not control other manufacturers speakers,
we decided to provide extra output current to drive
these mismatched low impedances and to indicate the
REAL output power required to drive them. Therefore
the meter circuit in the MC7150 electronically measures
both voltage and current, multiplies them and displays
the REAL OUTPUT POWER IN WATTS.
Another important feature of these output
wattmeters is their ability to respond 95% full scale to
a single cycle tone burst at 2kHz. After voltage and
current are measured and multiplied, the product is fed
to a special circuit that accelerates the meter pointer
in the upward direction. When it reaches its peak, it
pauses only long enough for the human eye to perceive
its position, then returns to 0. Response is almost 10
times faster than a professional VU meter.
A front panel switch is provided to change the
meters to the WATTS HOLD mode of operation, fast
upward movement of the pointer but greatly increased
HOLD time at the peak of its travel. The highest power
output of the source material is thus recorded.
OUTPUT AUTOFORMERS
The unequaled expertise of Mclntosh in the
design and manufacture of output transformers is leg-
endary in the Hi Fi industry. In the MC7150 they
provide proper matching for 2, 4 and 8 ohm loads. They
protect your speakers from damage in the event of an
output transistor failure, provide low distortion power
transfer at frequencies well beyond human hearing and
deliver peak output currents in excess of 53 amperes.
PROTECTION CIRCUITS
Some manufacturers of power amplifiers
advertised that their products do not require or use
protection circuits and that such circuits compromise
performance. Mclntosh Laboratory agrees that diligent
measures are required to allow unrestricted performance,
but we also insist that protection circuits are desirable
and necessary to prevent amplifier or loudspeaker
damage due to abnormal circumstance and that they
actually enhance performance. The MC7150
incorporates seven protection circuits to enhance its
performance, assure its reliability and to protect
loudspeakers.
POWER GUARD
Power Guard, a unique feature of Mclntosh
amplifiers, assures that each channel of the MC7150
will deliver full power free of clipping distortion. Clipping
is caused when an amplifier is asked to produce more
power output than its design is capable of delivering
with low distortion. Amplifiers that are overdriven may
deliver large quantities of power when they are clipping
MC7150 Product Preview/Page 5
MClNTOSH LABORATORY INC., 2 CHAMBERS STREET, BlNGHAMTON, NEW YORK 13903