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%. Mclntosh
has extended the life of its amplifiers by engineering for cool operation. Long life of a Mclntosh is not
just a claim.
fiers produced since 1949 are still in service today.
More
than
80% of the
Mclntosh ampli-
Mclntosh 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 Mclntosh de-
signed and manufactured auto-transformer.
The Mclntosh output circuit uses bipolar epitaxial
output transistors in a cleverly inventive design
that keeps the circuit components 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. AH this occurs without the
crossover distortion found in conventional solid
state output circuits. (The amplifier circuit is a patented Mclntosh design U.S. patent #3526847.)
The Mclntosh output stages are mounted on heat
sinks that have maximum surface area 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. Cooling air, flowing through the air tunnel,
easily dissipates any life limiting heat generated.
Here's a third benefit of the Mclntosh autotransformer. It not only provides the output transistors
an ideal load and is the path that conducts any DC
away from the loudspeaker, it 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 Mclntosh autotransformer perfectly matches the output circuit to
1, 2, 4 or 8 ohms. In mono, (Mclntosh stereo ampli-
fiers can be interconnected for mono and deliver
twice the power) the autotransformers provide
matching ½,1, 2, 4, 8 or 16 ohms. In addition, in
either stereo or mono, the autotransformer provides a 25 volt output that may be used to feed
multiple loudspeakers for background music and
the like. Truly, the Mclntosh autotransformer is an
engineering marvel that enhances amplifier performance without any technical or performance
drawbacks.
VERSATILE MclNTOSH POWER
AMPLIFIERS DELIVER FULL POWERALWAYS
The superior Mclntosh output circuit demands a
superior method of coupling the amplifier output
to the loudspeaker load. The Mclntosh designed
and manufactured autotransformer is a silent giant
that insures better performance and protection
and superior interaction between amplifier and
speaker. Its use provides many unseen benefits.
The autotransformer interconnection insures com-
plete stability of the amplifier. Other amplifier circuits need additional component considerations to
prevent instability with its subsequent threat to the
life and performance of the amplifier. It is the ideal
method of matching the output circuit to the loudspeakers. Transistors, used in amplifier output circuits, are designed to work into an optimum low
impedance load. Frequently amplifier performance
will
be
compromised
tions with frequency or by the use of multiple
speakers which modify the impedance as seen by
the output of the amplifier. Without the Mclntosh
autotransformer, variables, such as these, can
cause restricted performance, output transistor
heating and then circuit failure.
A second benefit of the Mclntosh autotransformer
is the protection provided in the event of a failure in
the output circuit. Should any direct current com-
ponent appear at the output, the autotransformer
will
conduct
ground. Your expensive loudspeakers are protected from this potentially damaging circumstance.
the
by
speaker
speaker
damaging
impedance
DC
varia-
directly
to
THE MclNTOSH (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 deliver up to 4O% harmonic distortion.
Distortion decreases the pleasure and enjoyment of
listening. This form of distortion (clipped signal)
also
produces extra
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 increased distortion —(3) protects your
speaker from excessive heating. Power Guard is a
patented Mclntosh design (U.S. patent #4048573).
heat
energy
which
will
damage
MC
2155/MC
POWER METERS
2255
USE
McINTOSH
The lack of accurate performance in ordinary meters has presented difficult and complex problems.
Ordinary meters are incapable of indicating the
short interval information in a sound wave. Short
interval information can have a duration of onehalf 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. Mclntosh engineering solved both problems by developing new electronic circuits the
meters
will
respond
to
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, peak-locking
meter circuit is a patented Mclntosh design (U.S.
patent #4065682).
A variety of information can be displayed on the
meters, power in watts, to lock and hold only the
highest power indications, or three different peakreading peak-locking decibel indications.
THE McINTOSH AUTOMATIC TEST
SYSTEM
The Mclntosh Automatic Test System provides per-
formance 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 mal-
function. You are informed when each test is veri-
fied by an LED number indicator.
THE McINTOSH "ALWAYS IN STYLE"
The appearance of a Mclntosh 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 panels are
selected to be free from bubbles, flow marks and
other faults. It is reverse silk screened with thermal
setting epoxy screen inks which practically become
a part of the glass. A brightly polished and anodized frame surrounds the glass. Knobs, meticuously machined of solid aluminum then anodized
and thermally and electrically isolated, compliment the overall appearance.
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.
The aluminum "Pro-Panel" on the MC 2150 and
MC 2250 is a combination of anodized gold and attractive baked enamel. Its versatility permits ease
of custom installation, installation in the Mclntosh
furniture cabinet or can be easily converted to professional rack mounting with accessory adapters.
The deletion of the meters and their associated
controls and circuits are the only electrical differences between these high performance models.
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 comple-
ment
any
decorative
scheme
and
will
remain
in
"good taste".
ince 1949, Mclntosh 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 Mclntosh
research, research that responds to
the demands for quality performance improvements. The U.S. Patent
Office has granted Mclntosh 30 patents which recognize these unique
and pace setting electronic designs.
Current Mclntosh amplifiers use one
or more of these U.S. Patents:
4065682; 4048573; 3526847; and
3526846.
But, patents only verify the engineering superiority and design integrity.
QUALITY
ance promised —and performance
delivered —over a long trouble-free
life. The Mclntosh reputation for
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. Mclntosh engineers
developed the Sentry Monitory Circuit which monitors operating conditions of the output stages of the
amplifier. If a Mclntosh 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
(#3526846).' Mclntosh 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
is
expressed
McINTOSH
in
perform-
QUALITY
QUALITY is acknowledged world
wide: QUALITY performance, QUAL-
ITY appearance, QUALITY manufac-
ture, and QUALITY protection. Each
component selected for use in a Mclntosh is quality tested not only for
assures
you of
long term
enjoyment
PERFORMANCE PROTECTION
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. Mclntosh
protects your investment.
Protection
3. In ordinary solid state circuits
failure
damaging direct current components to flow to the loudspeakers.
With the Mclntosh 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. Mclntosh protects your in-
vestment.
Protection
4. Mclntosh gives you a moneyback
performance guarantee. We promise
you that when you purchase a new
Mclntosh from a Mclntosh franchised
in the
output
stage
can
cause
performance but for maintaining
that performance over the long life
expected of a Mclntosh. At Mclntosh,
everyone and everything is dedicated to continuation of proven —
McINTOSH QUALITY.
through
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.
Mclntosh is the only manufacturer
that makes this statement. Mclntosh
protects your listening and your investment.
Protection
5. To assure you of the Mclntosh belief in design for long life, Mclntosh
goes beyond the ordinary guarantee.
You are offered a Mclntosh 3 Year
Service Contract which protects you
from
the
cost
of
years. Should your Mclntosh instru-
repair
ment fail, Mclntosh 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. Mclntosh protects
your investment.
for
three
full
PERFORMANCE GUARANTEE
Performance Limits are the maximum deviation from perfection permitted for a Mclntosh instrument. We
promise you that the amplifier you buy must be capable of performance at or exceeding these limits or you get
your money back. Mclntosh is the only manufacturer that makes this guarantee.
MC
MC
2255
MC 225O
MC 2155
215O
(Stereo, Both Channels Operating)
POWER OUTPUT
(Mono)
POWER BAND WIDTH
TOTAL HARMONIC DISTORTION
(250 mW to Rated Power,
20 Hz to 20
OUTPUT LOAD
kHz)
IMPEDANCE
Mono
INTERMODULAR ON DISTORTION
(250 mW to Rated Power)
FREQUENCY RESPONSE
(20 Hz to 20 kHz, at 1 Watt)
NOISE AND HUM
(Below Rated Output)
OUTPUT VOLTAGE
(For Distribution Systems)
DAMPING FACTOR
INPUT IMPEDANCE
INPUT SENSITIVITY
POWER REQUIREMENT
SEMICONDUCTOR COMPLEMENT
Transistors
Diodes
Integrated Circuits
DESIGNED AND ENGINEERED
UNDER THESE
U.S. PATENTS
Panel Height
SIZE Panel Width
Depth
FINISH
WEIGHT
In Carton
HEAT SINK AREA
250 Watts Minimum
Per Channel
500 Watts Minimum
20 Hz to 20 kHz
0.02% Maximum
Stereo
1, 2, 4, 8 Ohm
½, 1, 2, 4, 8, 16 Ohm
+ 0,
25 Volts
greater than 30
50,000 Ohm
0.75 or 2.5 Volts
120V,
0.7 to 12 Amp
4065682
4048573
3526847
3526846
7-1/8" (18.1cm)
16-3/16" (41.1cm)
14-1/2" (36.8cm)
Black Glass Panel,
Gold/Teal Nomenclature,
Gold and Black Knobs
82# (37.2kg)
96# (43.5kg)
1080
0.02%
-0.25
-95 dB
50/60
85
47
14
sq. in
dB
Hz
250 Watts Minimum
Per Channel
500 Watts Minimum
20 Hz to 20 kHz
0.02% Maximum
1, 2, 4, 8 Ohm
½, 1, 2, 4, 8, 16 Ohm
0.02%
+ 0,
-0.25
dB
-95 dB
25 Volts
greater than 30
50,000 Ohm
0.75 or 2.5 Volts
120V,
50/60
76
37
Hz
9
0.7 to 12 Amp
4048573
3526847
3526846
6-31/32" (17.7cm)
16" (40.6cm)
14-1/2" (36.8cm)
Gold Panel
Gold and Black
Knobs
80# (36.3kg)
94# (42.6kg)
1080
sq. in.
150 Watts Minimum
Per Channel
300 Watts Minimum
20 Hz to 20 kHz
O.02% Maximum
1, 2, 4, 8 Ohm
½, 1, 2, 4, 8, 16 Ohm
0.02%
+ 0,
-0.25
dB
-95 dB
25 Volts
greater than 30
50,000 Ohm
0.75 or 2.5 Volts
120V,
50/60
0.7 to 6 Amp
Hz
81
47
14
4065682
4048573
3526847
3526846
5-7/16" (13.8cm)
16" (40.6cm)
14-1/2" (36.8cm)
Black Glass Panel,
Gold/Teal Nomenclature
Gold and Black Knobs
65# (29.5kg)
7 7# (35kg)
772 sq. in
150 Watts Minimum
Per Channel
30O Watts Minimum
20 Hz to 20 kHz
0.02% Maximum
1, 2, 4, 8 Ohm
½, 1, 2, 4, 16 Ohm
0.02%
+ 0,
-0.25
dB
-95 dB
25 Volts
greater than 30
50,000 Ohm
0.75 or 2.5 Volts
120V,
50/60
0.7 to 6 Amp
4048573
3526847
3526846
5-7/32" (13.2cm)
16" (40.7cm)
14-9/16" (37cm)
Gold Panel
:, Gold and Black
Knobs
58" (26.3kg)
71" (32.2kg)
772 sq. in
Hz
72
37
9
Franchised Dealer:
O39487
Printed in U.S.A.
2
CHAMBERS
The continuous improvement of its products is the policy of
Mclntosh Laboratory Incorporated who reserve the right to
improve design without notice
McINTOSH LABORATORY INC.
ST.,
BINGHAMTON,
N.Y.
13903-2699
607-723-3512
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