Mclntosh MC50 Solid State Power Amplifier Owner’s Manual
- June 13, 2024
- Mclntosh
Table of Contents
MC50
OWNER’S MANUAL
THE McINTOSH MC 50 SOLID STATE POWER AMPLIFIER
MC50 Solid State Power Amplifier
READING TIME 20 MINUTES
Price $1.25
Your MC 50 Solid State Power Amplifier will give you many years of pleasant
and satisfactory performance. If you have any questions please contact:
CUSTOMER SERVICE
Mcintosh Laboratory Inc.
2 Chambers Street
Binghamton, New York 13903
Phone: 607-723-3512
WARNING: TO PREVENT FIRE OR SHOCK HAZARD, DO NOT EXPOSE THIS UNIT TO RAIN
OR MOISTURE.
Take Advantage of 3 years of FREE Factory Service…
Fill in the Application NOW.
THREE YEAR FACTORY SERVICE CONTRACT
An application for a FREE THREE YEAR FACTORY SERVICE CONTRACT is included with
this manual.
The terms of the contract are:
- Mcintosh will provide all parts, materials and labor needed to return the measured performance of the instrument to the original performance limits free of any charge. The SERVICE CONTRACT does not cover any shipping costs to and from the authorized service agency or the factory.
- Any Mcintosh authorized service agency will repair all Mcintosh instruments at normal service rates. To receive the free service under the terms of the SERVICE CONTRACT, the SERVICE CONTRACT CERTIFICATE must accompany the instrument when taken to the service agency.
- Always have service done by a Mcintosh authorized service agency. If the instrument is modified or damaged, as a result of unauthorized repair the SERVICE CONTRACT will be cancelled. Damage by improper use or mishandling is not covered by the SERVICE CONTRACT.
- The SERVICE CONTRACT is issued to you as the original purchaser. To protect you from misrepresentation this contract cannot be transferred to a second owner.
- For your protection Mcintosh selects its dealers carefully. Only one dealer in ten qualifies for a Mcintosh franchise. To receive the SERVICE CONTRACT your purchase must be made from a Mcintosh franchised dealer.
- Your completely filled in application for a SERVICE CONTRACT must be postmarked within 30 days of the date of purchase of the instrument.
- To receive the SERVICE CONTRACT all information on the application must be filled in. The SERVICE CONTRACT will be issued when the completely filled in application is received at Mcintosh Laboratory Incorporated in Binghamton, New York.
Copyright © 1972 By Mcintosh Laboratory Inc.
Installation
Adequate ventilation extends the troublefree life of electronic instruments.
It is generally found that each 10° centigrade (18° F) rise in temperature
reduces the life of electrical insulation by one half. Adequate ventilation is
an inexpensive and effective means of preventing insulation breakdown that
results from unnecessarily high operating temperatures. The direct benefit of
adequate ventilation is longer, trouble-free life.
The suggested minimum space for mounting the MC 50 is 14 inches long X 8%
inches wide X 9% inches high. Always allow for air flow by either ventilation
holes or space next to the bottom of the amplifier and a means for the warm
air to escape at the top.
It is recommended that the MC 50 be mounted in a normal or horizontal
position. However with adequate ventilation, the amplifier can be mounted in
any position except upside down. If the amplifier is to be installed on a
vertical surface it is recommended that
the autoformer be on the down side. This position permits greater air flow
around the transistors and component parts extending the trouble-free life of
the amplifier.
How to Connect
INPUT
The input sensitivity of the MC 50 is 0.5 volt for 50 watts output. The
input impedance is 200,000 ohms. There is a GAIN control in the input circuit
to permit the use of input voltages up to 30 volts. The input jack marked 0.5
VOLT INPUT is located below the GAIN control. Plug the shielded lead from the
program source in the INPUT jack.
OUTPUT
Speakers are connected at the barrier strips marked OUTPUT on the sloped
panel of the amplifier. Use lamp cord, bell wire, or wire with similar type of
insulation to connect the speakers to the amplifier. For the normally short
distances of under 50 feet between the amplifier and speaker, #18 wire or
larger can be used. For distances over 50 feet between the amplifier and
speaker use larger wire.
The loudspeaker impedance is usually identified on the loudspeaker. Connect
one of the leads from the loudspeaker to the screw marked COM on the OUTPUT
barrier strip. Connect the other lead from the loudspeaker to the screw marked
with the number corresponding to the speaker impedance on the OUTPUT barrier
strip.
The only adverse effect on the operation of a McIntosh amplifier when it is
improperly matched is a reduction in the amount of distortion-free power
available to the loudspeaker. Close impedance matching is desirable for
maximum distortion-free power.
SPEAKER CONNECTIONS
Use this table to determine proper speaker connection:
If the speaker impedance is between:| Connect the speaker leads between COM
and:
---|---
3.2 to 6.5 ohms| 4 ohms
6.5 to 13 ohms| 8 ohms
13 to 26 ohms| 16 ohms
For 25 volt line operation connect one of the leads to the screw marked COM on
the OUTPUT barrier strip. The other lead is connected to the screw marked 16
on the OUTPUT barrier strip.
AC POWER
The MC 50 operates on 105 voit to 130 volt, 50 to 60 Hz. The amplifier will be
turned on and off if its power cord is plugged in one of the auxiliary AC
power outlets on the program source.
FUSE
The MC 50 is fused with a slo-blo type fuse rated at 1.5 amperes. For maximum
protection always replace with fuses of the same rating, never larger. The AC
power outlet on the MC 50 is not fused.
Adjustments
For maximum flexibility set the amplifier gain control as follows: turn the volume control on the program source equipment (i.e. tape recorder, tuner, preamplifier, etc). to the 12 o’clock position. Turn the gain control on the MC 50 until the loudness of the sound from the speaker is just a little louder than you normally like to listen. The volume control on the program source equipment now has the most convenient amount of loudness change in either direction from the 12 o’clock position.
How to Connect
Performance Limits
PEP FORMANCE GUAR ONTEE
Performance Limits are the maximum deviation from perfection permitted for a
Mcintosh instrument. We promise you that the MC 50 you buy must be capable of
performance at or exceeding these limits or you get your money back. Mcintosh
is the only manufacturer that makes this guarantee.
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 entertainment products.
POWER OUTPUT
50 watts minimum sine wave continuous average power output, operating into 4
ohms, 8 ohms, or 16 ohms load impedance, which is:
14.1 volts RMS across 4 ohms
20.0 volts RMS across 8 ohms
28.3 volts RMS across 16 ohms
OUTPUT LOAD IMPEDANCE
4 ohms, 8 ohms, or 16 ohms; separate terminals are provided for each output
RATED POWER BAND
20 Hz to 20,000 Hz
TOTAL HARMONIC DISTORTION
0.25% maximum harmonic distortion at any power level from 250 milliwatts to 50
watts from 20Hz to 20,000 Hz
INTERMODULATION DISTORTION
0.25% if instantaneous peak power output is 100 watts or less for any
combination of frequencies 20 Hz to 20,000 Hz
FREQUENCY RESPONSE
20 Hz to 20,000 Hz +0 —0.25 db
10 Hz to 100,000 Hz +0 —3.0 dB at one watt output
NOISE AND HUM
90 dB below rated output
RATINGS
OUTPUT VOLTAGES
25 volts for distribution lines
DAMPING FACTOR
25 at 4 ohms output
50 at 8 ohms output
17 at 16 ohms output
INPUT IMPEDANCE
200,000 ohms
INPUT SENSITIVITY
0.5 volt. Level control provided for higher input voltage
GENERAL INFORMATION
POWER REQUIREMENTS
120 volts, 50/60 Hz, 15 watts at zero signal output, 120 watts at rate output
SEMICONDUCTOR COMPLEMENT
12 silicon transistors
12 silicon rectifiers and diodes
MECHANICAL INFORMATION
SIZE
5½ inches high (13.97 cm), 8 inches wide (20.32 cm),
12½ inches deep (31.75 cm)
CHASSIS
Chrome and black
WEIGHT
20 pounds (9.07 kg) net, 24 pounds (10.89 kg) in shipping carton
SPECIAL FEATURES
The amplifier is completely stable when connected to any loudspeaker system or
even to any reactive loads. The MC 50 has special circuits to prevent damage
by short circuit or open circuit of the output load, or by any amount of
output impedance mismatch.
Thermal cutouts are mounted on the output transistor heat sinks to provide
protection in the event of inadequate ventilation.
Typical Performance Charts
Technical Description
A two stage preamplifier with three transistors increases the input voltage
16db.
There are 13 transistors in the power amplifier section. The two stage
preamplifier is fed to a pair of matched transistors arranged as an emitter
coupled amplifier with two inputs and one output. The signal from the
preamplifier section connects to one of these inputs. Both AC and DC negative
feedback are applied to the other input. This large quantity of feedback is
used to reduce noise and distortion. The signal is then fed to a voltage
amplifier. The voltage amplifier is followed by two driver transistors.
The output section is arranged as a series pushpull amplifier. The power
transistors used in the output section of your MC 50 are selected for their
high power dissipation capability, wide frequency response, and large “safe
operating area.” In addition, each power transistor is given four separate
tests before it is put in your MC 50. This additional testing makes sure your
MC 50 will deliver its rated power from 20 Hz to 20,000 Hz with low distortion
and complete reliability.
The power transistors are mounted on oversized anodized heat sinks. The heat
sinks assure that under normal operation the transistors will operate at a low
temperature. If temperatures increase due to a shorted speaker, or restricted
ventilation, an automatic temperature sensing device turns off the power to
the MC 50. The device operates automatically at a preset temperature. The MC
50 will turn on again when the temperature has returned to normal limits.
This additional feature gives your MC 50 completereliability under the most
extreme operating conditions.
The output stages are matched to the load by the McIntosh autoformer. The
Mcintosh autoformer is carefully wound using Mcintosh trifilar winding and
interleaving techniques. Trifilar winding and interleaving gives the
autoformers exceptional bandwidth. The autoformers properly match the power
transistors to 4, 8 and 16 ohm loads at all audio frequencies.
The use of the Mcintosh designed trifilar autoformer makes the Mcintosh solid
state amplifiers the only amplifiers that deliver FULL POWER AT ALL SPEAKER
IMPEDANCES. You have not been power penalized for your choice of loudspeakers
when using the Mcintosh MC 50.
Another of the advantages of the autoformers is the 25 volt output for a
constant voltage distribution system. With the MC 50 several sets of speakers
can be operated independently throughout your home.
To further insure reliability a special power output SENTRY MONITORING CIRCUIT
prevents failure of the power output transistors due to excessive mismatch of
the output. When your MC 50 operates normally the SENTRY MONITORING CIRCUIT
has no effect on signals passing through the power amplifier. If the power
dissipation should rise above normal operation, the SENTRY MONITORING CIRCUIT
restricts the drive to the output transistors. The SENTRY MONITORING CIRCUIT
acts instantaneously for any input signal or load combination. This
arrangement assures complete circuit reliability. Only Mcintosh gives you this
degree of protection.
There are three separate power supply sections. One positive and one negative
high current supply is used for the output stages. The other positive supply
is used for the driving amplifier stages. All supplies are full wave and use
silicon rectifiers. Adequate filtering is used to assure an absolute minimum
of hum. The power output stage filter capacitors have very high capacity,
which allows full power output below 20 Hz. The power transformer is generous
in size and runs cool, even under heavy use.
Block Diagram
McINTOSH PROTECTION
FIRST PROTECTION—-
In these dark days of hurry up—percentage analysis—production rush—and
limited personal responsibility the McIntosh policy of ‘Performance Limits” is
a bit of bright blue sky. Every Mcintosh instrument— every one—is tested to be
equal to or better than the performance limits advertised. When a performance
limit of 0.25% harmonic distortion is established for an instrument, Mcintosh
means that every, each, all of the instruments manufactured must be capable of
performance to that limit—or better—or your full purchase price is refunded.
One of the reasons Mcintosh can make this promise is: we 100% test every
product for maximum performance. We are not content knowing that 10% of our
products are tested and meet the performance requirements established by our
engineering group. We must know that every one meets its requirements. This
vigorous pursuit of excellence takes time. At Mcintosh more time means more
care, more protection for you. There’s no production rush at Mcintosh.
The Mcintosh investment in professional testing instruments is staggering. On
a percentage basis McIntosh probably invests more of its sales dollars in
testing facilities that anyone else in a like business. For instance, Mcintosh
has one professional distortion analyzer for every 10 employees. This kind of
statistic is repeated for all sorts of test instruments. As new testing
instruments are produced that update the MclIntosh ability to know, Mcintosh
invests in them—wave form analyzers—real time analyzers—lowest distortion
signal generators—etc., etc. Even so far as a small FM transmitter so that the
entire transmission/reception system can be analyzed.
“What does this mean to me?” you ask. Only through this impressive investment;
through continuous testing and research; through product analysis; and endless
measurement can we promise and deliver to you reliability, long life,
performance, highest value, and freedom from service.
SECOND PROTECTION
Mcintosh Laboratory has great
belief in its engineering, product development, manufacturing and quality
control. To offer you strong evidence of this confidence Mcintosh offers you a
FREE THREE YEAR SERVICE CONTRACT. During the first three years you can’t spend
one dime for service. Mcintosh quarantees parts and labor. It costs you
nothing. The extended life of a Mcintosh, the conservative ratings, and the
sophisticated appearance make a Mcintosh instrument a greater value when you
are ready to trade.
McINTOSH LABORATORY INC.
2 CHAMBERS ST., BINGHAMTON, N. Y. 13903
607-723-3512
Design subject to change without notice.
Printed in U.S.A.
038-794
Documents / Resources
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Mclntosh MC50 Solid State Power
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[pdf] Owner's Manual
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