McIntosh MC-50 User's Manual

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Standard Y Ercelenco because …
The Mcintosh “will to perfection” requires that we probe
constantly into the unknown to bring the performance of our
electronic equipment closer to perfection than ever before.
This requires a constant and relentless search for low noise,
broad band conservative design with an ever lower distortion
factor. This is not required of ordinary equipment of average
designs. It is, for us, a costly but worthwhile scientific and
engineering effort. Our continuing research benefits our cus-
tomers with the almost complete lack of obsolescence and
the most reliable equipment ever made. It also means the
lowest long-range cost to you. Nearly all of the Mcintosh
equipment ever made is still useable, or in use, though it
may have been made twenty years ago.
CONTENTS
GENERAL DESCRIPTION ......... 2
TECHNICAL DESCRIPTION . ...... 2-3
BLOCK DIAGRAM . 1111111110 4
SPECIFICATIONS ....... . . 5
CONTROL PANEL INFORMATION .. 7
HISTACLATMIOÓN кана к поселок р 0.2 7
TYPICAL HOOKUP ... ......... 8
CONNECTING =. =... .. 9
PERFORMANCE CHARTS ... ..... 10
OPERATING =... ... « 31
GUARANTEE закопать й ой ва шо: . 12
Thank Th...
for purchasing the Mcintosh MC 50. To
insure your enjoyment please read this
manual carefully and follow instructions.
We know you will enjoy countless hours
of musical pleasure from this instrument.
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TECHNICAL DESCRIPTION
A two stage preamplifier with three transistors increases the input
voltage 16 dB. The two stage preamplifier is fed to a pair of
matched transistors arranged as an emmiter 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 push-pull 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 to 20 kHz with low distortion
and complete reliability.
The power transistors are mounted on an oversized anodized heat
sink. The extra large heat sink assures that under normal opera-
tion the transistors will operate at a low temperature. If tempera-
tures increase due to a shorted speaker, or restricted ventilation,
an automatic temperature sensing device turns off 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 complete reliabil-
ity under the most extreme operating conditions.
The output stages are matched to the load by the Mcintosh auto-
former. The Mcintosh autoformer is carefully wound using Mcln-
tosh trifilar winding and interleaving techniques. Trifilar winding
and interleaving gives the transformers exceptional bandwidth.
The autoformers properly matched 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 autoformer is the 25 volt output
for a constant voltage distribution system. With the MC 50 sev-
eral sets of speakers can be Operated independently throughout
your home.
To further insure reliability a special power output SENTRY MONI-
TORING 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 SEN-
TRY MONITORING CIRCUIT restricts the drive to the output
transistors. The SENTRY MONITORING CIRCUIT acts instantane-
ously for any input signal or load combination. This arrangement
assures complete circuit reliability. Only Mcintosh gives you this
degree of protection.
Melnfosh
MC 50
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PERFORMANCE
CHARTS
POWER vs FREQUENCY
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0.25% HARMONIC DISTORTIQN \
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10 50 100 500 1K 5K 10K 50K 100K
FREQUENCY IN HERTZ
| EQUIVALENT POWER OUTPUT vs
INTERMODULATION DISTORTION
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PERCENT HARMONIC DISTORTION
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PERCENT INTERMODULATION DISTORTION
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1 10 20 30 40 50 60 70 80 20100 1 10 20 30 40 50 60 70 80 90100
POWER OUTPUT IN WATTS RMS POWER OUTPUT EQUIVALENT WATTS AMS
SPECIFICATIONS
MC 50
ELECTRICAL SPECIFICATIONS:
POWER OUTPUT:
50 RMS watts continuous into 4, 8, or 16 ohms.
HARMONIC DISTORTION:
Less than 0.25% at 50 watts power output
from 20 Hz to 20 kHz. Typical performance is
less than 0.1% at rated power. Distortion de-
creases as output power is reduced.
INTERMODULATION DISTORTION:
Less than 0.25% if instantaneous peak power
output is 100 watts or less for any combina-
tion of frequencies 20 Hz and 20 kHz.
FREQUENCY RESPONSE:
20 Hz to 20 kHz +0, —0.1 dB at 50 watts
10 Hz to 50 kHz +0, —0.5 dB at 50 watts
7 Hz to 100 kHz +0, —3.0 dB at 25 watts
NOISE AND HUM:
90 dB or more below rated output.
OUTPUT IMPEDANCE:
4 8, and 16 ohms.
OUTPUT VOLTAGES:
25 volts
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 volts. Level control provided for higher
input voltage.
POWER REQUIREMENTS:
117 volts AC 50/60 Hz, 15 watts at zero sig-
nal output, 120 watts at 50 watts output.
SEMICONDUCTOR COMPLEMENT:
12 Silicon Transistors
12 Silicon Rectifiers and Diodes
MECHANICAL SPECIFICATIONS:
SIZE: 5% inches high, 8 inches wide, 12% inches
deep.
CHASSIS: Chrome and black.
WEIGHT: 20 pounds net, 24 pounds in shipping
carton.
SPECIAL FEATURES
The amplifier is completely stable when con-
nected to any loudspeaker system or to any re-
active load. The MC 50 has special circuits to
prevent damage by short circuit or open circuit
of the output loads, 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.
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CONTROL PANEL INFORMATION
OUTPUT GAIN
1.5 A SLO-BLO
117 Y 50-60 Hz 15-110 WATTS
117 V AC 400 WATTS
INPUT
The input jack is located below the GAIN control.
The input sensitivity of the MC 50 is 0.5 volt for 50 watts output. The in-
put 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.
OUTPUT
Output connections are provided on the output barrier strip for the normal
speaker impedances of 4 ohms, 8 ohms, and 16 ohms. Connection at the
terminal strips may be made for a constant voltage output of 25 volts.
FUSE
The MC 50 uses a 1.5 ampere slo-blo type fuse. The auxiliary AC outlet
is not fused.
AC OUTLET
The auxiliary AC outlet can be used to supply power to other equipment
in the system. The outlet will provide a maximum of 400 watts of power.
The AC outlet is not fused.
LINE VOLTAGE
The MC 50 operates on any line voltages between 117 volts and 130 volts,
50 to 60 Hz.
AC POWER
The MC 50 operates on 117 to 130 volt, 50/60 Hz. The amplifier will be
turned on and off if its power cord is plugged in one of the auxiliary AC
outlets on the program source.
INSTALLATION
Adequate ventilation extends the trouble-free 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 un-
necessarily high operating temperatures. The direct benefit of
adequate ventilation is longer, trouble-free life.
The suggested minimum space for mounting the MC 50 is 20
inches long x 9% inches wide x 11% 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 ampli-
fier 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 autoformers be on the down side. This position permits
greater air flow around the transistors and component parts
thereby extending the trouble-free life of the amplifier.
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TYPICAL HOOK UP
REMOTE MONOPHONIC
SPEAKER
LEFT MAIN
SPEAKER
CENTER CHANNEL
SPEAKER
RIGHT MAIN
SPEAKER
LEFT REMOTE
SPEAKER
RIGHT REMOTE
SPEAKER
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PREAMPLIFIER
MC 50 MC 50 MC 50 _
CENTER CHANNEL LEFT CHANNEL RIGHT CHANNEL pS ms
L E A M P L | F | E R AMPLIFIER DUTPUT MAIN SPEAKERS MOTE SPEAKERS INPUTS
AMPLIFIER AMPLIFIER e IR | Soo 0 e-
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CONNECTING THE MC50
1.5 A SLO-BLO
117 Y 50-60 Hz 15-110 WATTS
OUTPUT
GAIN
INPUT The shielded cable from the program source is
plugged into the INPUT jack.
OUTPUT Speakers are connected at the output barrier strip
on the sloped panel of the amplifier. Use lamp
cord, bell wire, or wire with similar type of insula-
tion to connect the speakers to the amplifier. For
the normally short distances of under 50 feet be-
tween 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 itself. Connect one lead 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 Mc-
Intosh 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.
Use this table to determine proper speaker connection:
If the speaker impedance
is between:
3.2 to 6.5 ohms
6.5 to 13 ohms
13 to 26 ohms
Connect the
speaker leads
between COM and:
4 ohms
8 ohms
16 ohms
INPUT
10
BLOCK DIAGRAM MC 50
GAIN
PRE -AMP.
AC
LINE
©
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POWER
INPUT AMP.
FEEDBACK
NETWORK
AMP.
©
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BIAS
“|NETWORK
CLASS B OUTPUT STAGE
POWER CONTROLLER
© ©
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QUTPUT
AUTOFORMER
POWER
TRANSFORMER
FUSE
FEEDBACK
NETWORK
O € --
CLASS B OUTPUT STAGE
POWER SUPPLY
AND
FILTER
16 A
8 2 SPEAKER
an OUTPUT
COM
OPERATING THE MC50 STEREO AMPLIFIER
SETTING THE GAIN CONTROL.
Turn the volume control on the source
equipment to the 12 o'clock position
(half rotation). Turn up the GAIN con-
trol on the MC 50 until the loudness in
the room is about as loud as you like to
listen. This setting allows the volume
control on the source equipment the
greatest range of operation and loud-
ness change.
11
Your MC 50 power amplifier will give you many years of pleasant and satis-
factory performance. If you have any questions concerning operation or
maintenance please contact the dealer from whom you purchased this
instrument or: —
CUSTOMER SERVICE
Mcintosh Laboratory Inc.
2 Chambers Street
Binghamton, N. Y. 13903
Our telephone number is
MC50 GUARANTEE NE Edesa
Mcintosh Laboratory Incorporated guarantees this equipment to be pa
capable of performance as advertised. We also guarantee the me-
chanical and electrical workmanship and components of this equip-
ment to be free of defects for a period of 90 days from date of
purchase. This guarantee does not extend to components damaged
by improper use nor does it extend to transportation to and from
the factory.
3 YEAR FACTORY SERVICE CONTRACT
An application for a FREE 3 YEAR FACTORY SERVICE CONTRACT
is included in the pack with this manual. The FREE 3 YEAR FAC-
TORY SERVICE CONTRACT will be issued by Mcintosh Laboratory
upon receipt of the completely filled out application form. The terms
of the contract are:
Transportation charges are excluded.
This agreement is given to the original purchaser only and is
not transferable.
The application for the contract must be filled out completely
If the instrument has been modified or damaged by unauthor-
ized repair the contract will be cancelled.
To receive free service, the contract must be presented to the
factory authorized service agency, when the equipment is pre-
sented for repair.
If the application is not received at Mcintosh Laboratory, only the
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A service offered under the standard 90 day guarantee will apply on NE
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12 SERVICE BY FILLING IN THE APPLICATION NOW
Melntosh
McINTOSH LABORATORY INC.
2 CHAMBERS ST., BINGHAMTON, N. Y. 13903
607-723-3512
Design subject to change without notice.
Printed in US A