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Meinfosh mx112
One Moment, Please
Your purchase of a McIntosh instrument shows
that you are a careful discriminating buyer. One who
is interested in quality performance, quality engi-
neering, quality manufacturing, and long trouble free
equipment life. You can protect your investment by
spending a few minutes reading this owner’s manual.
When you bought a McIntosh, you bought count-
less hours of musical pleasure and superior perform-
ance. Enjoy it!
FM-AM TUNER
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CONTENTS
GENERAL DESCRIPTION 2
TECHNICAL DESCRIPTION ..___ 3-5
BLOCK AGAN e y
SPECIFICATIONS ...... . ... 7
INK MORRY N N 8
CABINET INSTALLATION .. 9
CONNECTIONS .............. .. 10-11
FRONT PANEL CONTROLS ...... 12-13
BALANCINS 11 14
USING YOUR STEREO .......... 15
GUARANTEE... .......... 16
INPUT SELECTOR >
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GENERAL DESCRIPTION
Thank you for your
selection of a Mcintosh.
You have selected the very best.
SILER.
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The MX 112 combines in one unit an ex-
tremely low-distortion preamplifier with a
highly sensitive FM multiplex tuner and
an AM tuner for added and complete lis-
tening pleasure. The INPUT SELECTOR
gives you a choice of six different pro-
gram sources.
The Mcintosh MX 112 is a beautifully
engineered tuner/control center for the
finest stereo sound systems.
The MX 112 is completely solid state, with
the exception of the tuning indicator. The
solid state devices used in the MX 112 are
considered “very new” in the state of the
art of solid state physics.
The extreme care in manufacturing, in
layout design and in quality control prom-
Ises the usual Mcintosh extra values of
reliability, performance, and long life.
Other values added to this tuner are:
careful control of circuit constants dur-
during testing, very high sensitivity, and
and excellent spurious response re-
jection.
Every desirable feature of a tuner and
preamplifier is included in this design.
FM interstation noise suppression (mut-
ing), tuning indicator, FM multiplex indi-
cator, individual channel bass and treble
controls, and electronic phase switch
have all been engineered into the MX 112.
The Mcintosh designed PANLOC system
is the first professional installation tech-
nique to be used on stero instruments.
The PANLOC system gives you absolute
ease of installation, operation and main-
tenance.
By releasing the PANLOC buttons on the
front panel, you can slide the MX 112 out
of its mounting until the second latch en-
gages. The top mounted controls for
interstation noise suppression (muting),
phase switching and front panel lighting
are now available.
MX 112
TECHNICAL DESCRIPTION
FM SECTION:
The FM consists of two separate modu-
lar sections:
A THE RF SECTION:
This section houses the complete FM
front-end and part of the AM-RF cir-
cuit.
The FM circuit employs three junc-
tion field effect transistors, two of
which form the very high frequency
amplifier in a series-fed “cascode”
type circuit, giving maximum gain at
minimum thermal noise.
This VHF amplifier is preceded by a
double-tuned circuit and is followed
by a mixer circuit employing the third
junction field effect transistor and a
single-tuned circuit.
The FM local oscillator is designed
for minimum response to tempera-
ture variations, making automatic fre-
quency control unnecessary. The
drift rate is less than 10 parts per
megahertz per degree centigrade.
The RF circuits of the MX 112 are
completely shielded and exceed the
FCC requirements for suppression of
oscillator radiation.
Either a 300 ohm or 75 ohm antenna
may be used with the MX 112.
A VHF television antenna which is
suitable for FM reception can be con-
nected to the MX 112. For maximum
performance we recommend a good
FM yagi or log-periodic antenna with
rotator.
B THE FM-IF AND DETECTOR
SECTION:
This section employs two integrated
circuit devices, each capable of am-
plifying the intermediate frequency
signal from the mixer by a thousand
times (60 db). Lumped selectivity in
the form of two sets of quadruple-
tuned bandpass filters insure good
intermediate frequency skirt selectiv-
ity.
The tuned circuits that make up the
bandpass filters are designed for
electrical stability and for electrical
and mechanical resistance to shock
and vibration.
“Hard” limiting is accomplished by
the use of the two integrated circuits.
The limiting is complete at very low
levels of input signals.
A phase or Foster-Seeley discrimi-
nator is used as the FM detector, and
is designed for extremely low har-
monic distortion in the recovered
output signal. With the “Hard” limit-
ing properties of the preceding two
stages a low capture ratio is obtained.
FM STEREO MULTIPLEX SECTION:
The multiplex section uses a special Mc-
Intosh developed detecting circuit. A par-
ticular advantage of this circuit is the
elimination of the critical adjustments
necessary with commonly used matrix-
ing circuits. This circuit detects the L — R
sidebands and automatically matrixes
the recovered information with the LER
main carrier signal to yield the left and
right program output with maximum sep-
aration.
The 19KC pilot signal is filtered from the
composite stereo input signal, amplified
by a special limiting amplifier, doubled
to the 38KC carrier frequency, and then
amplified again by a limiting amplifier.
The composite signal minus the 19KC
pilot is combined with the 38KC carrier
signal and fed to the special detector cir-
cuit mentioned above. Balanced full wave
detectors are used to cancel the 38KC
components in the output.
A three section phase linear sharp cut off
filter rejects SCA interference without de-
stroying stereo separation.
FM muting, automatic FM stereo switch-
ing, and an FM stereo indicator are also
part of the multiplex section. The FM
muting operates by detecting ultra-sonic
noise which is present when tuning be-
tween stations or when receiving a weak
station. The FM muting operates equally
Well, of course, when receiving mono or
stereo stations. The automatic FM stereo
switching activates the stereo multiplex
circuits when receiving FM stereo. On
mono FM stations this circuit is inactive
and therefore maximum signal to noise
ratio is assured at all times.
The FM stereo indicator is lit when the
tuning dial pointer crosses a station
broadcasting FM stereo. The light does
not indicate when tuning between the
stations.
AM SECTION:
The AM circuit employs only field-effect
transistors for top performance, in-
creased reliability, and temperature sta-
bility.
The use of dual-insulated gate, field-
effect transistors in the RF and Mixer cir-
cuits insures freedom from cross-modu-
lation and overloading by strong local
stations.
A 10kHz whistle filter is connected at the
detector output to attenuate any hetero-
dyne that occurs due to the frequency
separation between adjacent AM carriers.
A highly-sensitive loopstick antenna is
provided. An outside antenna may be
used for added “pulling-in” capabilities.
TUNING MECHANISM and DIAL DRIVE:
In the MX 112, a new type of mechanical
tuning assembly gives smooth flywheel
tuning.
By controlling the relationship of mass
and mechanical resistance, and by divid-
ing the workloads in the dial drive system,
it becomes nearly impossible to detect
any backlash. Yet, the entire dial drive is
a model of mechanical stability.
The tuning capacitor rotors of both AM
and FM sections are mounted on the
same shaft.
For added ease and increased tuning
accuracy, a section of the dial pointer-is
illuminated.
4
PHONO PREAMPLIFIER
There are three transistors in each chan-
nel of the phono preamplifier. The output
of the third transistor is connected by
a negative feedback loop to the emitter
‚of the input transistor. The feedback loop
reduces noise and distortion. It also pro-
vides precision RIAA frequency compen-
sation required for magnetic phonograph
cartridges. Feedback remains in effect
even at 20 Hz, where gain is highest. The
negative feedback also provides a low
output impedance for the tape output.
Phono input overload is virtually impos-
sible. For example, at 1000 Hz, the phono
input can accept 150 millivolts of signal
without overload. Ten millivolts of signal
at the phono input at 1000 Hz will pro-
duce 1.2 volts at the tape output. More
than adequate for recording on tape.
The selector switch connects either the
output of the phono amplifier, the FM
tuner section, the AM tuner section or a
high level input to the main preamplifier.
The high level input impedance is 250,-
000 ohms. The high level input feeds: di-
rectly to the volume control. A loudness
contour circuit is connected to a tap on
the volume control to provide loudness
compensation. Compensation can be
switched in or out. The high level signal
then feeds to a pair of transistors con-
nected as high gain amplifiers.
In the left channel the second transistor
is connected in a balanced output ar-
rangement. This circuit provides equal
amplitude signals so that the output level
does not change when the phase is
reversed. Negative feedback is used
around this pair of transistors to reduce
noise and distortion. The negative feed-
back provides the low impedance need-
ed to drive the highly selective filter net-
works which follow.
The filter networks can be switched in or
out. The high-frequency filter network re-
duces treble response above 5000 Hz.
The low-frequency filter reduces bass re-
sponse below 50 Hz. The slope of the
filters is selected for maximum rejection
of commonly encountered noise. Careful
design keeps the loss of usable program
material to a minimum.
The output from the filter circuits is fed
into the balance control. The output of
the balance control drives the first stage
of the tone control section. The remain-
ing two transistors are connected as a
high-gain amplifier stage. The high-gain
of this stage is used to advantage for the
tone. control negative feedback circuits.
Negative feedback in the tone control
circuits assures low distortion and accu-
rate shape on the tone-control response
curves. Negative feedback is maintained
at all fregencies, even with the tone con-
trols turned to full boost. Overall distor-
tion is low at all frequencies including
frequencies where maximum boost oc-
curs. The negative feedback also pro-
vides the low impedance output required
for the main preamplifier outputs.
CENTER CHANNEL AMPLIFIER
The L+R amplifier consists of asingle
transistor connected as a voltage am-
plifier. Negative feedback is used
around the voltage amplifier to main-
tain low distortion and provide a low
impedance for the center channel
output.
POWER SUPPLY:
The power supply of the MX 112 has
received very special design atten-
tion.
Two separate rectifier circuits are
used. First, a full-wave rectifier sup-
plies D.C. to all audio circuits. The
second full-wave rectifier supplies
D.C. to all tuner and multiplex-de-
coder circuits.
Both power supplies are very elabor-
ate in design. They use electronic fil-
tering to insure the lowest possible
background hum level, maximum sta-
bility, and extremely good regulation.
Melntosh
MX 112
MX 112 BLOCK DIAGRAM |
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SPECIFICATIONS
FM
USABLE SENSITIVITY: Better than 2.5 microvolts at 100%
modulation (+75 kHz deviation) for less than 3% total
noise and harmonic distortion (IHF)
FREQUENCY RESPONSE: +1 dB from 20 Hz to 20,000 Hz
with standard de-emphasis and 19,000 Hz pilot filter
HARMONIC DISTORTION: Mono, less than 0.5% at 100%
modulation +75 kHz deviation
IMAGE REJECTION: Better than 80 dB at 100 MHz better
than 70 dB at 105 MHz
SPURIOUS REJECTION: Better than 100 dB
CAPTURE RATIO: Better than 1.8 dB
DRIFT: Less than 25,000 Hz
ose AND NOISE: Better than 65 db below 100% modu-
ation
TUNING INDICATOR: Electron Ray for simple accurate
center of channel tuning
STEREO INDICATOR: Stereo light activated by 19 kHz
carrier only
AM
SENSITIVITY: Better than 12 microvolts at 1,000 kHz
(using external antenna input)
SIGNAL TO NOISE RATIO: Better than 55 dB
jor DISTORTION: Less than 1% at 30% modu-
ation
FREQUENCY RESPONSE: Down 6 dB at 5,000 Hz and 34
dB at 10,000 Hz
SELECTIVITY: 10,000 Hz at —6 dB
IMAGE REJECTION: 60 dB or greater at 1000 kHz
PREAMPLIFIER SPECIFICATIONS
FREQUENCY RESPONSE: +0.5 db 20 to 20,000 Hz
DISTORTION: Less than 0.1% at 2.5 volts output, 20 to
20,000 HZ
INPUT SENSITIVITY AND IMPEDANCE: PHONO 1 and
piers 2: 2 millivolts at 47,000 ohms for 2.5 volts
output,
AUX TAPE: .25 volts at 250,000 ohms for 2.5 volts
output
MXT112 SPECIFICATIONS
HUM AND NOISE: PHONO 1 and PHONO 2: 70 dB below
10 millivolt input; equivalent to less than 3 microvolts
at the input terminals
AUX-TAPE: 85 dB below rated output
QUTPUT: MAIN: 2.5 volts with rated input. Up to 10 volts
can be developed without distortion
TAPE: 2.5 volts with rated input
L + R: 2.0 volts with rated input
QUTPUT IMPEDANCE: MAIN: 200 ohms, designed to
operate into 47,000 ohms or more
TAPE OUTPUT: About 200 ohms, designed to operate
into 47,000 ohms or more
(L + В): About 1,200 ohms, designed to operate into
47,000 ohms or more
TRANSITOR COMPLEMENT:
4 Junction FET
4 MOS FET
27 Silicon Planar
2 Integrated Circuits (each contains the equivalent of
10 transistors and 7 diodes)
1 6HU6 tuning indicator
20 diodes
POWER REQUIREMENTS: 117/125 volts, 50/60 Hz, 30
watts.
MECHANICAL SPECIFICATIONS
SIZE: Front panel: 16 inches wide by 5%, inches high:
Chassis: 15 inches wide by 13 inches deep, including
PANLOC shelf and back panel connectors; Knob Clear-
ance: 1% inches in front of mounting panel
WEIGHT: 24 pounds net, 36 pounds in shipping carton
FINISH: Front panel: Anodized gold and black with special
gold/teal panel nomenclature illumination
CHASSIS: Chrome and black
MOUNTING: Mcintosh developed professional PANLOC
FACILITIES
BASS CONTROL: —20 dB to + 16 dB at 20 Hz. Clutch
sou aa controls for independent adjustment of each
channe
TREBLE CONTROLS: +20 dB at 20,000 Hz. Clutch
pe controls for independent adjustment of each
channe
LOUDNESS: Flat response, or compensated for low listen-
ing levels
BALANCE: When program material is out of balance, ro-
tation of the balance control returns the program to
natural balance
VOLUME CONTROL: Precision ‘‘tracked” to —60dB so
that proper stereo balance is maintained. AC ON/OFF
switch is coupled with the volume control
TAPE MONITOR SWITCH: Push button; compares re-
corded tape with program source while recording
VOLTAGE AMPLIFICATION:
AUX, TAPE
To MAIN output 20 dB
To TAPE output 0 dB
PHONO 1, PHONO 2
To MAIN output 62 dB
To TAPE output 42 dB
AC OUTLETS:
1 unswitched (Red)
2 switched
LF FILTER: Flat, or roll-off below 50 Hz, 6 dB per octave,
down 12 dB at 20 Hz
HF FILTER: Flat, or roll-off above 5 kHz, 6 dB per octave,
down 12 dB at 20,000 Hz
INPUT SELECTOR: 6 positions: AUX (auxiliary or spare),
TAPE, AM, FM, PHONO 1, and PHONO 2
MODE SELECTOR: Pushbutton, STEREO, or MONO
SECONDARY CONTROLS
PHASE CONTROL: Electronically reverse phase in the left
channel to correct “out of phase" program sources
MUTING ADJUST: Modifies the noise rejection threshold
DIAL SCALE INTENSITY: Modifies the briteness of the
illumination of the front panel
Melntosh
MX 112
IF YOU'RE IN A INPUT SELECTOR
тт
AUX: Any program source requiring flat amplification
is connected to the AUX jacks on the back panel.
TAPE: The output of a tape recorder with its own
electronics is connected to the TAPE jacks on the
back panel.
AM: For listening to the AM section of the MX 112.
FM: For listening to the FM section of the MX 112.
PHONO 1: The output of a record player or turntable
is connected to the PHONO 1 jacks on the back
panel.
PHONO 2: The output of another record player or
turntable is connected to the PHONO 2 jacks on
the back panel.
TREBLE: Modifies the high frequency program ma-
terial to suit your taste. The right channel is the
large knob, the left channel is the small knob.
BASS: Modifies the low frequency program material
to suit your taste. The right channel is the large
knob, the left channel is the small knob.
BALANCE: Adjusts for equal loudness in each chan-
nel when the program source has unequal channel-
to-channel volume.
VOLUME ON/OFF: Turns the MX 112 “ON” and ad-
justs loudness of the sound.
PUSHBUTTONS:
MODE SELECTOR: Push IN for MONO; OUT for
STEREO.
HF: Push IN: Reduces high frequencies to sup-
press unwanted record noise, etc.; OUT: Flat
| LT TY : response. :
wx 112 TUNER PREA ry LF: Push IN: Reduces low frequencies to suppress
CH I Sr unwanted rumble; OUT: Flat response.
E aros ооо „(Ai TAPE: Push IN: Monitor the recorded program
from the tape. Push OUT: Hear the program that
is being recorded.
MUTING: in the IN position the muting is turned on.
Weak stations that may not override noise and
interference are suppressed by the muting. In the
OUT position, the muting is turned off. This allows
conventional FM tuning with the noise and inter-
ference present. Use this position to tune weak
or noisy stations.
LOUDNESS: Push IN: Adjusts bass as volume is re-
duced to compensate for average hearing losses
at low volume.
entr Jon
On the back of the cabinet panel, scribe a vertical line
through the exact center of the area to be cut out.
Place the MOUNTING TEMPLATE #100 against the back
of the panel. Make sure there is at least % inch clearance
between the bottom of the cutout (dashed line on the tem-
plate) and any shelf or brace below the proposed cutout.
Mark the back of the cabinet panel with a pointed instru-
ment through the two “C” locating holes. Drill through the
cabinet panel with a small diameter drill. Be certain the
drill is perpendicular to the panel.
Position the MOUNTING TEMPLATE #100 on the front of
the panel. Align the “C” holes in the template with the
drilled holes in the cabinet panel.
Holding the template in place against the cabinet panel,
mark the “A” and “B” drill holes and the four corner holes.
Join the corner marks with a pencil. The edge of the tem-
plate can be used as a straight edge.
Drill the three holes on each side with a % inch drill being
careful to make them accurate as to location.
Cut out the rectangular opening. Saw on the inside of the
pencil lines.
Secure the mounting strips to the rear of the cabinet
panel using two screws from the hardware package. Use
two % inch long screws for panels under % inch, or two
1% inch long screws for panels % inch thick and. larger.
10.
11.
12.
Insert the screws in the center holes of the cabinet panel
(“B” holes on the template) and tighten into the center clip
of the mounting strips. The screw head should pull into
the wood slightly.
Attach the PANLOC brackets to the back of the cabinet
panel using four screws. (“A” holes on the template.)
Prepare the PANLOC unit for mounting by removing the
four plastic feet that are secured by screws to the bottom
of the chassis.
Insert the power cord through the opening. Carefully slide
the unit into the opening so the aluminum rails on the bot-
tom of the unit engage the grooves in the metal mounting
brackets. Continue to slide the unit until it stops at the
adjust position.
VERTICAL INSTALLATION
In the hardware packet are two helical springs. Fasten the
springs to the small flanges at the rear of the PANLOC
brackets. The flange has a notch and a hole to mount the
spring. The springs assist in the removal of vertically
mounted PANLOC equipment.
DO NOT USE THE SPRINGS ON HORIZONTALLY MOUNTED EQUIPMENT.
CONNECTING A RECORD PLAYER TO
PHONO 1
Connect the “left” channel to the “up-
per” PH 1 input jack.
Connect the “right” channel to the
“lower” PH 1 input jack.
PHONO 2 position is used if two rec-
ord players are used in a system. Con-
nect the “left” channel to the “upper”
PH 2 input jack. Connect the “right”
channel to the “lower” PH 2 input jack.
CONNECTING A TAPE RECORDER TO
RECORD
Connect the MX 112 output jacks
marked TAPE to the high level inputs
of the tape recorder.
CONNECTING A TAPE RECORDER FOR
PLAYBACK
Connect the “left” channel recorder
output to the “upper” TAPE 1 input
jack.
Connect the “right” channel recorder
output to the “lower” TAPE 1 input
jack.
CONNECTING THE MX 112 TO POWER
AMPLIFIERS
Connect the output jacks marked
MAIN to the input of a stereo power
amplifier. The upper jack is connected
to the LEFT amplifier input jack. The
lower jack is connected to the right
amplifier input jack.
The output impedance atthe MAIN out-
put is 200 ohms. Longer cables than
are normally supplied can be con-
nected between the MX 112 and the
CONNECTING YOUR MX I12
amplifiers. The length of the cable is
limited by the capacity of the cable.
The total capacity must not exceed
1000 pF. For instance: cables with a
capacity of 25 pF per foot may be 40
feet long; 13.5 pF per foot cable may
be 75 feet long. The input impedance
of the amplifiers should be 47,000 ohms
or greater.
CONNECTING AN FM ANTENNA
Monophonic installations that are sat-
isfactory on an indoor antenna may
require the use of an outdoor antenna
for equivalent results. Satisfactory
stereo requires about 10 times as
much signal from the antenna.
With the MX 112 one of three an-
tenna systems can be used: (1) the in-
door dipole supplied with the MX 112,
(2) an outdoor FM antenna, or (3) a
VHF-TV antenna. In fringe areas best
results will probably be obtained with
the use of an outdoor FM antenna. In
many areas the indoor dipole antenna
may be satisfactory. The use of a VHF-
TV antenna is also effective in many
installations.
CONNECTING AN INDOOR DIPOLE
ANTENNA
The flexible folded dipole antenna (300
ohm) supplied with the MX 112 is for
indoor use in urban or high strength
signal areas.
Connect the two leads from the dipole
to the terminals marked FM ANT (red).
The flexibility of the thin flat wire as-
sembly permits it to be placed under a
rug, tacked behind the stereo .. . or,
placed in any other convenient loca-
tion. In some cases, it may be neces-
sary to “position” the antenna for best
signal reception. This should be done
before it is permanently located or
tacked down.
CONNECTING AN OUTDOOR FM
ANTENNA
An outdoor antenna is recommended
for optimum performance in all areas.
In fringe (outlying) areas, best results
will be obtained with a highly direc-
tional FM antenna used in conjunction
with a rotator. Rotate the antenna un-
til the best reception is obtained. Con-
nect the 300 ohm antenna to the termi-
nals marked FM ANT (red).
CONNECTING A 75 OHM COAXIAL
ANTENNA
An unbalanced 75 ohm antenna can be
connected to the MX 112 with coaxial
cable. Connect the center conductor
to the left FM ANT (Red) connector.
The shield is connected to the GND
(black) connector.
The Mcintosh designed balun matches
the 75 ohm input to the tuner for opti-
mum performance.
AC OUTLETS
There are 2 black AC outlets and one
red AC outlet. The power to the black
AC outlets is controlled by the front
panel switch. Use these outlets for a
tuner, tape recorder, etc. The red re-
cepticle is on at all times. Use the red
outlet for aturntable or record changer.
The turntable is protected by this ar-
rangement. It is necessary to turn off
the turntable or record changer: with
its own AC switch.
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RIGHT SPEAKER
CONNECTING THE MX112
12
FRONT PANEL CONTROLS
INPUT SELECTOR
AUX: Connects the back panel input jacks
(AUX) to the MX 112. Has flat amplifica-
tion. The gain is 20 dB to the MAIN out-
puts. The gain is 0 dB to the TAPE out-
puts.
TAPE: Connects the back panel input
jacks (TAPE) to the MX 112. Has flat am-
plification. The gain is 20 dB to the MAIN
outputs. The gain is 0 dB to the TAPE
outputs.
AM: Connects the AM tuner portion of
the MX 112 to the output jacks.
FM: Connects the FM tuner portion of the
MX 112 to the output jacks.
PHONO 1: Connects the back panel jacks
(PH 1) to the MX 112. The amplification
has been compensated for magnetic
phono cartridges. The gain is 62 dB to
the MAIN outputs and 42 dB to the TAPE
outputs. The input impedance is 47,000
ohms.
PHONO 2: Connects the back panel jacks
(PH 2) to the MX 112. The amplification
has been compensated for magnetic
phono cartridges. The gain is 62 dB to
the MAIN output and 42 dB to the TAPE
outputs. The input impedance is 47,000
ohms.
BASS
The BASS is a concentric control. The
large outer knob controls the low fre-
quency response in the right channel.
The small center knob controls the low
frequency response in the left channel.
The two knobs are friction coupled. This
permits them to be adjusted together or
independently. Clockwise rotation in-
creases lows and counterclockwise de-
creases lows. Position the control to the
center position for flat response.
TREBLE
The TREBLE is a concentric control. The
outer knob controls the high frequency
response in the right channel. The small
center knob controls the high frequency
response in the left channel. The two
knobs are friction coupled. This permits
them to be adjusted together or inde-
pendently. Clockwise rotation increases
highs and counterclockwise decreases
highs. Flat is the center position.
BALANCE
The BALANCE control adjusts for un-
equal volume in either the left or right
channels. The volume of each channel
can be varied relative to each other with-
out affecting their combined loudness.
Turning the control left accentuates the
left channel by reducing the loudness in
the right channel. Turning the control
right accentuates the right channel by
reducing the loudness in the left channel.
VOLUME ON/OFF: Turning the VOLUME
control totally counterclockwise turns the
MX 112 OFF. The VOLUME control regu-
lates the loudness in both channels. The
VOLUME control has been precision
tracked throughout the listening range
(0 to-65dB) for accurate stereo balance.
PUSHBUTTONS
MODE SELECTOR: STEREO: The left
channel is heard from the left loud-
speaker and the right channel is heard
from the right loudspeaker.
INPUT SELECTOR
MONO (L+R): The left and right chan-
nels are added together and are heard
from both loudspeakers.
LF FILTER: With the push button pushed
in the low frequency response is attenu-
ated below 50 Hz. The slope is 6 dB per
octave. Use of the LF filter reduces un-
wanted low frequency noise such as
rumble. With the push button released,
the response of the MX 112 is flat.
HF FILTER: With the push button pushed
IN the high frequency response is attenu-
ated above 5 kHz. The slope is 6 dB per
octave. Use of the HF filter reduces un-
wanted high frequency noise like hiss or
scratch. With push button released, the
response of the MX 112 is flat
TAPE: The TAPE push button is used to
monitor tape as it is being recorded. With
the push button IN, the recorded tape is
heard. Release the button and the pro-
gram being recorded is heard. Instan-
taneous comparison of recorded material
and the program source is provided by
Т
УГО
MX 112 TUNER PREAMPLIFIER
=e, +. TAME HUTINE-- LOUB- +++
the use of the TAPE push button. IM-
PORTANT: When the MX 112 is operated
with the TAPE push button in the IN posi-
tion, signal from any other source will not
be heard from the loudspeakers. When
not in use make sure the push button is
in the “OUT” position.
MUTING: Muting suppresses the back-
ground noise and hiss normally heard
between stations. With the control in the
IN position the muting is turned on. Weak
stations that may not override noise and
interference are also suppressed by the
muting. In the OUT position, the muting
is turned off. This allows conventional
FM tuning with the noise and interfer-
ence present. Use this position to tune
weak or noisy stations.
LOUDNESS
When the volume is turned down, the
music will seem to lose much of its bass.
As volume is reduced the response of
the human ear to bass decreases more
rapidly than its response to notes cen-
BALANCE
VOLUME
tered in the midtonal range. The LOUD
push button automatically provides the
correct amount of bass and treble boost
required to compensate for this change
in response of the human ear at low-
loudness levels. When the “LOUD” button
is pushed to the IN position, it converts
the volume control to a loudness com-
pensated control. Use the LOUD IN to
listen at low volume and still hear full-
frequency range.
PANLOC
Mcintosh developed PANLOC mounting
brings professional installation tech-
nique to stereo. Depressing the PANLOC
buttons (as with a ball point pen) will
release the instrument. It can then be slid
forward to the “adjustment” position. In
the “adjust” position the top panel con-
trols PHASE, MUTING and DIAL SCALE
INTENSITY can be adjusted.
13
YOUR STEREO
LISTENING TO A STEREO RECORD
1. Turn the INPUT SELECTOR to PHONO 1 or
PHONO 2, whichever is connected to the record
player you wish to hear.
2. Make certain the MODE PUSHBUTTON is in the
OUT or STEREO position.
3. Adjust the VOLUME control to desired volume.
LISTENING TO A MONOPHONIC RECORD
1. Turn the INPUT SELECTOR to PHONO 1 or
PHONO 2, whichever is connected to the record
player you wish to hear.
2. Push the MODE pushbutton IN to MONO.
3. Adjust the VOLUME control to desired volume.
LISTENING TO A STEREO TAPE RECORDER
The TAPE input is used:
1. Turn the INPUT SELECTOR to TAPE.
2. Set the MODE pushbutton to STEREO or MONO,
depending on the program on the tape.
3. Adjust the VOLUME control to desired volume.
To monitor while recording, the tape recorder
must have separate record and playback heads.
The TAPE pushbutton permits monitoring the
tape recordings while in the process of record-
ing. When the TAPE pushbutton is in the IN
position it will play the sound from the tape as it
passes the playback head, a moment after it is
recorded. The recording process continues as
usual. When the TAPE pushbutton is in the OUT
position the program being recorded is heard.
LISTENING TO FM or FM STEREO
1. Turn the INPUT SELECTOR to FM.
2. Adjust the volume to a comfortable level.
3. Rotate the tuning knob to the station of your
choice.
The MX 112 uses a new Mcintosh devel-
oped automatic mono-stereo switching cir-
cuit. The switching is electronic without
switching clicks or transients.
The circuit switches smoothly and silently
when the 19KC multiplex carrier is present.
When the STEREO indicator is lit, the sta-
tion is broadcasting a 19KC carrier. This
signal causes the automatic circuit to
switch the MX 112 to stereo. If a station
is broadcasting monophonic FM program,
the STEREO indicator will remain off and
the tuner will automatically switch to
mono. The ultrasonic muting circuit sup-
presses all noise between stations. It sup-
presses all weaker stations not strong
enough to override the background noise.
The muting threshold setting determines
the strength of the signal which can be
heard with muting in operation. The muting
threshold is carefully adjusted to optimum
at the factory. Casual adjustment of the
muting threshold is not recommended.
While tuning you may notice that the tun-
ing indicator will show a station yet no pro-
gram is heard from the speakers. The mut-
ing circuit in the tuner is rejecting the sta-
tion because there is objectionable noise
with the weak signal from the station. Push
the MUTING pushbutton to the OUT posi-
tion and the station will be heard. Most
programs that can be tuned in this manner
are of poor quality due to interfering noise.
LISTENING TO AM
Set the INPUT SELECTOR to AM.
2. Adjust the volume to a comfortable level.
3. Rotate the tuning knob to the station of
your choice.
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