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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 com-
ponent selected for use in a
McIntosh is quality tested not only
for performance but for maintain-
ing that performance over the
long life expected of a McIntosh.
At McIntosh, everyone and
everything is dedicated to con-
tinuation of proven-McIntosh
quality.
Since 1949, McIntosh has con-
tinuously expanded the boun-
daries 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 re-
search, research that responds to
the demands for quality perfor-
mance 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 pro-
mised - 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 engineer-
ing for cool operation. McIntosh
cool operation requires a com-
bination of careful design of the
output circuit, containing the out-
put circuit in a mechanical hous-
ing that permits the use of gener-
ous 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 auto-
transformer.
The McIntosh output circuit
uses bipolar epitaxial output tran-
sistors in a cleverly inventive
design that keeps the circuit com-
ponents cool, extending the long
trouble-free life of the com-
ponents. The circuit has the abili-
ty 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 oc-
curs without the crossover distor-
tion 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 cap-
ability, the largest for equivalent
power in the industry. The super
sized heat sinks are placed in an
air tunnel chassis design that oc-
cupies 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 impos-
ed higher power demands on to-
day's amplifiers. Poorly designed
amplifiers, of which there are
many, can present music listeners
with a form of harsh unpleasant
distortion due to amplifier over-
load {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 distor-
tion. Distortion decreases the
Oscillogram of output waveform with and wilhout Power Guard.
Input overdriven for each trace 20 dB.
pleasure and enjoyment of listen-
ing. This form of distortion (clip-
ped signal) also produces extra
heat energy which will damage
most speakers. McIntosh leader-
ship in engineering has developed
the Power Guard circuit
which-(1) dynamically prevents
power amplifiers from being over-
driven into hard clipping-(2)
assures that the amplifier will
produce its maximum output
without increased distortion-(3)
protects your speaker from exces-
sive 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 cir-
cuits the meters are made to res-
pond to short intervals with an ac-
curacy 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 vi-
sion characteristics of the human
eye. The peak-reading, peak-
locking 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 con-
tinuous updating as higher powers
are delivered or you may select
from three different peak-reading,
peak-locking decibel indications.
Each selected function is in-
dicated 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 perfor-
mance at seven critical points in
the amplifier's circuits. The Auto-
matic Test System verification
assures operational readiness
before operation starts and limits
any damage should there be com-
ponent malfunction. Each time a
test is verified an LED number in-
dicator 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 ther-
mally and electrically isolated.
Anodizing is an electro-chemical
process that leaves a color dyed
and hardened surface that is im-
pervious 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
2150.
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.
