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McIntosh MC 2155
150 Watt Per Channel
Power Amplifier
Oplional Walnut Veneer
Cabinet
The Word For
EXCELLENCE
Handcrafted with pride in the United States by dedicated highly trained craftspeople.
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The MC 2155...150 WATTS OF PURE PERFORMANCE
The McIntosh reputation for
QUALITY is acknowledged world
wide: quality performance, quality
appearance, quality manufacture,
and quality protection. Each component selected for use in a
McIntosh is quality tested not only
for performance but for maintaining that performance over the
long life expected of a McIntosh.
At McIntosh, everyone and
everything is dedicated to continuation of proven-McIntosh
quality.
Since 1949, McIntosh has continuously expanded the boundaries of power amplifier
technology and performance with
the introduction of each new
design. What is considered to be
"State of the Art" has been the
starting line for McIntosh research, research that responds to
the demands for quality performance improvements. The U.S.
Patent Office has granted
McIntosh 30 patents which
recognize these unique and pace
setting electronic designs. Current
McIntosh amplifiers use one or
more of these U.S. Patents:
4,065,682; 4,048,573; 3,526,847;
and 3,526,846.
But, patents only verify the
engineering superiority and design
integrity. Quality is the desire that
is expressed in performance promised - and delivered-over a long
trouble-free life. McIntosh
superior quality has been long
recognized world wide.
MCINTOSH QUALITY
BEGINS WITH CAREFUL
DESIGN FOR COOL
OPERATION
To achieve long trouble-free life
in an amplifier it is essential to
have cool operation. As little as
one degree (centigrade) rise in
temperature can reduce the
operating life of the amplifier
10%. McIntosh has extended the
life of its amplifiers by engineering for cool operation. McIntosh
cool operation requires a combination of careful design of the
output circuit, containing the output circuit in a mechanical housing that permits the use of generous sized heat sinks to provide
great heat dissipation capability
along with chassis construction
that permits adequate ventilation,
then correctly matching the cool
operating output circuit to the
loudspeakers with a McIntosh
designed and manufactured autotransformer.
The McIntosh output circuit
uses bipolar epitaxial output transistors in a cleverly inventive
design that keeps the circuit com-
ponents cool, extending the long
trouble-free life of the components. The circuit has the ability to recognize the power
demands of the program material
and then to activate only as much
of the output circuit as is needed
to satisfy that demand. All this occurs without the crossover distortion found in conventional solid
state output circuits. (The
amplifier circuit is a patented
McIntosh design U.S. patent
#3526847.)
The McIntosh output stages are
mounted on heat sinks that have
772 square inches of cooling capability, the largest for equivalent
power in the industry. The super
sized heat sinks are placed in an
air tunnel chassis design that occupies the entire space from the
bottom of the amplifier to the top.
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Cooling air, flowing through the
air tunnel, easily dissipates any
life limiting heat generated.
THE MCINTOSH
(EXCLUSIVE) POWER
GUARD MUSIC
PROTECTION CIRCUIT
Improved recordings and
recording techniques have imposed higher power demands on today's amplifiers. Poorly designed
amplifiers, of which there are
many, 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 de-
liver up to 40% harmonic distortion. Distortion decreases the
Oscillogram of output waveform with and wilhout Power Guard.
Input overdriven for each trace 20 dB.
pleasure and enjoyment of listening. This form of distortion (clipped signal) also produces extra
heat energy which will damage
most speakers. McIntosh 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 increased distortion-(3)
protects your speaker from excessive heating. Power Guard is a
patented McIntosh design (U.S.
patent #4,048,573).
THE McINTOSH
POWER METERS
The lack of accurate perfor-
mance in ordinary meters has
presented difficult and complex
problems. Ordinary meters are
incapable of indicating the short
interval information in a sound
wave. The mass of the meter
movement is too great to respond
to the nearly instantaneous
changes in music program
material. That short interval
information can have a duration
as short as one-half of one
thousandth of a second. Even if
the meter were capable of such
high velocity movement, the
human eye could not perceive the
information. McIntosh engineering
solved both problems electrically.
By developing new electronic circuits the meters are made to respond to short intervals with an accuracy of 98%! To permit the eye
to see such high speed motion, the
electronic circuits that drive the
meter pointer are time stretched
so the meter pointer position can
register in the persistence of vision characteristics of the human
eye. The peak-reading, peaklocking meter circuit is a patented
McIntosh design (U.S. patent
#4,065,682).
A variety of information can be
displayed on the meters. You may
elect to observe the delivered
power in watts demanded by the
musical program or you may elect
to lock and hold only the highest
power indications yet have continuous updating as higher powers
are delivered or you may select
from three different peak-reading,
peak-locking decibel indications.
Each selected function is indicated by illuminated
nomenclature on the panel.
THE MCINTOSH
AUTOMATIC TEST
SYSTEM
The McIntosh Automatic Test
System provides positive perfor-
mance protection and extends the
long trouble-free life of an
amplifier. Each time the amplifier
is turned on, the Automatic Test
System electronically measures
and verifies accurate performance at seven critical points in
the amplifier's circuits. The Automatic Test System verification
assures operational readiness
before operation starts and limits
any damage should there be component malfunction. Each time a
test is verified an LED number indicator shows which test is being
performed.
This Automatic Test System
protects your investment.
THE MCINTOSH
"ALWAYS IN STYLE"
The appearance of a McIntosh
speaks eloquently of precision,
quality, premier performance and
long, trouble-free life. Consider
the construction and materials
used in the front panel and knobs.
Each constituent part is selected
for long, wear-resistant life and
stable attractive styling. The
panel of the MC 2155 is select
glass, free from bubbles, flow
marks and other faults. It is silk
screened on the reverse side with
thermal setting epoxy screen inks
which practically become a part
of the glass. Then it is built into a
brightly polished and anodized
frame. The knobs used are
meticulously machined of solid
aluminum then anodized and thermally and electrically isolated.
Anodizing is an electro-chemical
process that leaves a color dyed
and hardened surface that is impervious to attack from common
household cleaning fluids, oils and
acids from the skin and is highly
wear resistant.
This handsome combination of
glass, anodized aluminum and
epoxy requires very little
maintenance to keep that, "Just
new" appearance. The subtle yet
sophisticated styling is designed
to complement any decorative
scheme and will remain in
"good taste".
The MC 2150 front panel is an
attractive combination of textured
anodized aluminum and baked
enamel. The knobs are machined
of solid aluminum then anodized
for permanence.
INSTALLATION
WITH THE MC2155
The quality performance,
quality appearance, qualify
manufacture and quality
protection described for
the MC 2155 are repeated
in the MC
The "Pro-Panel" has an
attractive baked enamel
and gold anodized finish.
Its versatility permits ease
of custom installation, in-
stallation in the McIntosh
furniture cabinet or can be
easily converted to pro-
fessional rack mounting with
The deletion of the meters and
and circuits are the only
high performance models.
2150.
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PROTECTION
1. When ordinary amplifiers
are asked to exceed their design
maximum, or have an accidental
short circuit across the output or
a severe impedance mismatch, the
operating temperature of the output stages can rise very rapidly,
leading to cataclysmic failure.
McIntosh engineers developed the
Sentry Monitory Circuit which
monitors operating conditions of
the output stages of the amplifier.
If a McIntosh amplifier is asked to
exceed its design parameters, the
Sentry Monitor Circuit is activated which protects the output
transistors and helps to prevent
failure. The Sentry Monitor Circuit has been granted a U.S.
patent (#3,526,846). McIntosh protects your investment.
PROTECTION
2. A heat sensing switch attached to the super sized heat sinks
controls the AC power to the
amplifier. As long as temperatures are normal it does not
function; but, should the temperature of the heat sinks rise above
normal, the AC power is disconnected automatically until the
temperature returns to normal
when the AC power is restored.
McIntosh protects your investment.
PROTECTION
3. In ordinary solid state cir-
cuits failure in the output stage
can cause damaging direct current components to flow to the
loudspeakers. With the McIntosh
autotransformer, matching the
output circuits to the loudspeakers, any direct current
component is shunted to ground.
Your speakers are protected
completely from this kind of amplifier failure. McIntosh protects
your investment.
PROTECTION
4. McIntosh gives you a moneyback performance guarantee. We
promise you that when you purchase a new McIntosh from a
McIntosh franchised dealer, it
will be capable of or can be made
capable of performance at or exceeding its published performance
limits or you can return the instrument and get your money
back. McIntosh is the only
manufacturer that makes this
statement. McIntosh protects your
listening and your investment.
PROTECTION
5. To assure you of the
McIntosh belief in design for long
life, McIntosh goes beyond the ordinary guarantee. You are offered
a McIntosh 3 Year Service Contract which protects you from the
cost of repair for three full years.
Should your McIntosh instrument
fail, McIntosh will provide the service materials and labor needed
to return the measured performance at the original performance limits. The SERVICE CONTRACT does not cover any shipping costs to and from the authorized service agency or the factory.
McIntosh protects your investment.
ADAPTABILITY
accessory adapters.
their associated controls
ectrical differences between these two
MC 2150 with optional RMAS
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VERSATILE MCINTOSH
POWER AMPLIFIERS
DELIVER FULL POWER - ALWAYS
The McIntosh auto transformer
is a silent giant in insuring better
performance and protection. Its
use provides many unseen benefits. First, it is the ideal method
of coupling the output circuit to
the loudspeakers which are the
load into which the output of
the amplifier is fed. Frequently
the loudspeaker can compromise
amplifier performance by
speaker impedance variations
with frequency or by multiple
speakers connected to the amplifier. Because transistors, used
in amplifier output circuits are
designed to work into an optimum low impedance load, the
use of the McIntosh autotransformer matches these requirements best. Without the
McIntosh autotransformer, variables, such as these, can cause
output transistor heating, restricted performance and then
circuit failure.
A second benefit of the
McIntosh autotransformer is the
protection provided in the event
of a failure in the output circuit.
Should there be any direct cur-
rent component in the output circuit, the autotransformer conducts any speaker
damaging DC directly to ground.
Your expensive loudspeakers are
protected from this potentially
damaging circumstance.
A third benefit of the McIntosh
autotransformer, which not only
provides the output transistors an
ideal load and is the path that
conducts any DC away from the
loudspeaker, also contributes a
flexibility in loudspeaker connecting capability not otherwise
possible. For safe operation ordinary amplifier output circuits are
usually restricted to operate into
4 or 8 ohms. In stereo, the
McIntosh autotransformer per-
fectly matches the output circuit
to 1, 2, 4 or 8 ohms. In mono, (the
stereo amplifiers can be interconnected for mono operation while
delivering twice the power) the
autotransformers provide matching to ½, 1, 2, 4, 8 or 16 ohms.
And, in addition, the autotrans-
former provides a 25 volt output
in either stereo or mono, that may
be used to feed multiple loudspeakers for background music
and the like. Truly, the McIntosh
autotransformer is an engineering
marvel that enhances amplifier
performance without any technical or performance drawbacks.
The continuous improvement of its products is the policy of
McIntosh Laboratory Incorporated, who reserves the right to improve
design without notice.
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MC2155 / MC2150 PERFORMANCE LIMITS
Performance Limits are the
maximum deviation from perfec-
tion permitted for a McIntosh in-
strument. We promise you that
when you purchase a new
MC 2155 or MC 2150 from a
McIntosh franchised dealer, it
will be capable of or can be made
capable of performance at or exceeding these limits or you can
return the unit and get your
money back. McIntosh is the only
manufacturer that makes this
statement.
PERFORMANCE
McIntosh audio power ratings
are in accordance with the
Federal Trade Commission Regulation of November 4, 1974 concerning power output claims for
amplifiers used in home entertain-
ment products.
POWER OUTPUT
STEREO
150 watts minimum sine wave
continuous average power output,
per channel, both channels
operating into 1 ohm, 2 ohms, 4
ohms, or 8 ohms load impedance,
which is:
12.2 volts RMS across 1 ohm
18.3 volts RMS across 2 ohms
24.5 volts RMS across 4 ohms
34.6 volts RMS across 8 ohms
MONO
300 watts minimum sine wave
continuous average power output
into 0.5 ohm, 1 ohm, 2 ohms, 4
ohms, 8 ohms, or 16 ohms load impedance, which is:
12.2 volts RMS across 0.5 ohm
17.4 volts RMS across 1 ohm
24.5 volts RMS across 2 ohms
34.6 volts RMS across 4 ohms
49.0 volts RMS across 8 ohms
69.3 volts RMS across 16 ohms
OUTPUT LOAD IMPEDANCE
STEREO
1 ohm, 2 ohms, 4 ohms, and 8
ohms; separate terminals are pro-
vided for each output.
MONO-PARALLEL
0.5 ohm, 1 ohm, 2 ohms, and 4
ohms; obtained by connecting
together the appropriate terminals
of both channels.
MONO-BRIDGED
2 ohms, 4 ohms, 8 ohms, or 16
ohms, balanced to common con-
nections.
RATED POWER BAND
20 Hz to 20,000 Hz
TOTAL HARMONIC DISTORTION
STEREO
0.02% maximum harmonic distortion at any power level from 250
milliwatts to 150 watts from 20 Hz
to 20,000 Hz both channels
operating.
MONO
0.02% maximum harmonic distor-
tion at any power level from 250
milliwatts to 300 watts from 20 Hz
to 20,000 Hz.
INTERMODULATION
DISTORTION
STEREO
0.02% maximum if instantaneous
peak power output is 300 watts or
less per channel with both channels operating for any combination of frequencies, 20 Hz to
20,000 Hz.
MONO
0.02% maximum if instananeous
peak power output is 600 watts or
less for any combination of frequencies, 20 Hz to 20,000 Hz.
FREQUENCY RESPONSE (at one
watt output)
20 Hz to 20,00 Hz + 0 - 0.25 dB.
10 Hz to 100,000 Hz + 0.25 - 1 dB.
NOISE AND HUM
95 dB below rated output.
RATINGS
DAMPING FACTOR
Greater than 30
INPUT IMPEDANCE
50,000 ohms.
INPUT SENSITIVITY
Switchable: 0.75 volt or 2.5
volts-level control provided for
higher input voltages.
POWER GUARD
Clipping is prevented and THD
does not exceed 2% with up to 20
dB overdrive at 1 kHz.
GENERAL INFORMATION
POWER REQUIREMENTS
120 volts 50/60 Hz 0.7 to 12 amps.
SEMICONDUCTOR COMPLEMENT
MC2150 MC2155
72 silicon transistors 81
37 silicon rectifiers and diodes 47
9 integrated circuits 14
MECHANICAL INFORMATION
MC 2150 SIZE
16 inches wide (40.7 cm) by
5-7/32 inches high (13.2 cm), by
14-1/2 inches deep (36.8 cm), including connectors. Knob
clearance required is 1 inch (2.5
cm) in front of mounting panel
FINISH
Front panel is anodized gold.
Chassis is chrome and black
WEIGHT
58 pounds (26.3 kg) net, 71 pounds
(32.2 kg) in shipping carton
MC 2155 SIZE
16 inches wide (40.6 cm) by 5 7/16
inches high (13.8 cm), by 14-1/2 inches deep (36.8 cm), including
connectors. Knob clearance re-
quired is 1-3/16 inches (3 cm) in
front mounting panel
FINISH
Front panel is anodized gold and
black with special gold/teal
nomenclature illumination.
Chassis is chrome and black
WEIGHT
65 pounds (29.5 kg) net, 77 pounds
(35 kg) in shipping carton
Franchised Dealer:
039 436
Printed in U.S.A.
MCINTOSH LABORATORY INC.
2 CHAMBERS ST., BINGHAMTON, N.Y. 13903-2699
607-723-3512
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