The McIntosh
Tuner-Preamplifier unit concept accommodates all regular inputs of tuner,
phono, tape, etc., and allows the
selection of the right power amplifier needed for your system. The MX 113
is the most advanced version of this remarkable AM-FM/FM Stereo Tuner
preamplifier with switchable selectivity. It has performance beyond any other
manufacturer's equipment available today.
Special
Features
Multiple
"selectivity" switchable from the front panel. An elegant solution to
a tough problem.
Linear Phase
(constant delay) IF amplifier for low distortion at even high selectivity and
low distortion.
Steggered
tuning condenser elements to improve RF front and behavior, less interstage
coulping, lower spurious effect, higher Q circuits.
Tremendous
accomodiation of strong RF input signals - up to 10 volts without overload -
overcoming an aggravating limitation of conventional tuners.
Highest
spurious rejection 90 dB (IHF) and highest image rejection 95 dB (88 to 108
MHz). This means you receive the stations at the right place on the dial only.
You don't receive the same stations or some mixture as you tune across the
dial.
Ultra Sonic
"muting" provides smooth inter channel FM noise suppression. Has complete
connection to McIntosh Maximum performance Indicator to maximize your listening
pleasure.
McIntosh
developed a special detecting circuit used in the multiplex section. An
advantage of this circuit is the elimination of the critical adjustments
necessary with commonly used matrixing circuits. The circuit detects the L - R
side-bands, then automatically matrixes the recovered information with the L +
R carrier signal. This yialds the left and right program output with maximum
separation.
TUNING
MECHANISM AND DIAL DRIVE
In the MX
113, the unique design and careful manufacture of the mechanical assembly gives
smooth flywheel tuning. By controlling the relationship of mass and mechanical
resistance, and by dividing 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. For added ease and increased tuning accuracy, a
section of the dial pointer is illuminated.
FM SECTION
The Radio
Frequency (RF) section houses the complete FM-RF front-end and part of the AM
RF circuit. A seven-section variable capacitor is the heart of the RF section.
Four sections of the variable capacitor are in the FM front end and the
remaining three are in the AM section. By interleaving the sections
(AM-FM-AM-FM-etc.) spurious responses are significantly reduced. The four FM
sections of the variable tuning capacitor provides a high degree of RF
selectivity and excellent spurious rejection. Using the latest "state of
the art" field effect transistors with a welldesigned variable tuning
capacitor has provided the MX 113 with an excellent RF front-end ….
FM-IF AND
DISCRIMINATOR SECTION
The MX 113
uses linear-phase IF filters. Each filter was designed from a FORTRAN computer
program for minimumphase and constant delay. The mathematical complexity of the
filter design procedure is almost beyond belief. Using numerical integration in
the S-Plane, an "IBM" 1130 high speed computer spent eighteen minutes
on the mathematics for the design of the IF filter. It would have taken a human
engineer, working twenty-four hours a day, seven days a week, and working
error-free three-hundred years to perform the same mathematical calculations!
...
FM STEREO
MULTIPLEX SECTION
Mclntosh has
developed a special detecting circuit used in the multiplex section. A
particular advantage of this circuit is the elimination of the critical
adjustments necessary with commonly used matrixing circuits. The circuit
detects the L - R sidebands, then automatically matrixes the recovered
information with the L + R carrier signal. This yields the left and right
program output with maximum separation. ...
AM SECTION
The AM-RF
amplifier circuit includes a three section variable tuning capacitor in the
metal enclosed shielded RF module which also houses the FM-RF front end. A
three section variable capacitor is used for greater spurious rejection. The RF
amplifier is unique. The circuit has constant sensitivity, constant
selectivity, high image rejection across the complete AM band. Ordinary AM-RF
circuits cannot do all of these simultaneously. This circuit design achieves
equal sensitivity even at the low end of the band. Spurious, image, and
intermediate frequency rejection are all superior. The same circuit delivers
equal selectivity across the entire band. The Mclntosh circuit is unique in a
superheterodyne AM receiver ...
...The AVC
(automatic volume control) system was designed to prevent bursting or thumps
when the AM is tuned through a strong signal. Distortion at low audio
frequencies is minimized by using two AVC filter sections instead of the
conventional one.
PHONO
PREAMPLIFIER
There are
three transistors in each channel 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
provides precision RIAA frequency compenation 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.
...
L + R
AMPLIFIER
The L + R
amplifier consists of a single transistor connected as a voltage amplifier.
Negative feedback is used around the summing amplifier to maintain low
distortion and provide a low impedance for the center channel output.
POWER SUPPLY
The power
supply of the MX 113 has received very special attention.
Three
separate rectifier circuits are used. First, a fullwave rectifier supplies DC
to all audio circuits. The second full-wave rectifier supplied DC to all tuner
and multiplexdecoder circuits. The third supply provides DC to the AM circuit.
The power supplies are elaborate in design. They use electronic filtering to
insure the lowest possible background hum level, maximum stability, and
extremely good regulation.
Specifications
FM
Section
Useable
Sensitivity: 2.5 microvolts at 100% modulation (± 75 kHz deviation) for less than 3% total noise and harmonic
distortion,
Signal
to noise ratio: 70 dB at 100%
modulation,
Harmonic
Distortion:
Mono : Will not exceed
0.3% at 100% modulation ±75 kHz deviation.
Stereo : Will not exceed 0.5% at 100% modulation ±75 kHz deviation.
Frequency
Response: ±1dB from 20 Hz to 15,000 Hz
with standard de-emphasis
Capture
Ratio: 1.5 dB
Spurious
Rejection: 90 dB
Image
Rejection: 95 dB at 88 to 108 MHz (IHF)
Stereo Separation: Exceeds 35 dB at 1,000 Hz
Selectivity:
Switch
Setting : OUT /IN
Adjacent
Channel : 6 dB /15 dB
Alternate
Channel : 58 dB /88 dB
Tuning Indicator: D'Arsonval movement meter with increased sensitivity
Stereo Indicator: Stereo light activated by 19,000 Hz pilot signal only
AM Section
Sensitivity: 75 microvolts at 1,000 kHz (using external antenna input).
Signal To Noise Ratio: 45 dB
Harmonic Distortion: 1% at 30% modulation
Frequency Response: Down 6 dB at 3,500 Hz
Selectivity:
Switch
Setting : OUT/ IN
Adjacent
Channel : 35 dB/45 dB
Image Rejection: 65 dB; 540 kHz to 1600 kHz
Preamplifier Section
Frequency Response: ±0.5 dB, 20 to 20,000
Hz.
Distortion: Will not exceed 0.1%
at 2.5 volts output, 20 to 20,000 Hz.
Input
Sensitivity & Impedance:
Phono 1
and Phono 2: 2 millivolts for 2.5 volts output at 1,000 Hz, 47,000 ohms;
Auxiliary
and Tape: 0.25 volts for 2.5 volts output; 250,000 ohms.
Voltage
Amplification:
Phono
1, Phono 2 to Main output: 62 dB, to Tape
output: 42 dB.
Auxiliary,
Tape to Main output: 20 dB, to
Tape output: 0 dB.
Output:
Main: 2.5
volts with rated input. Up to 10 volts can be developed without increase in
distortion. FM will produce 10 volts output at 100% modulation.
Tape:
0.25 volts with rated input. Phono signal to 10 millivolts produces 1.2 volts
output. FM will produce 1 volt output at 100% modulation. L + R 2 volts with
rated input
Hum
& Noise:
Phono
1 and Phono 2: 72 dB below 10 millivolt input; (equivalent to less than 3 microvolts at the input terminals)
Aux-Tape:
85 dB below 2.5 volts output, (unweighted)
Bass
Control: -18 dB to + 16 dB at 20 Hz
Treble
Control: ±20 dB at 20,000 Hz
LF
Filter: Flat or roll off below 50 Hz, down 12 dB at 20 Hz
HF
Filter: Flat or roll off above 5,000 Hz, down 12 dB at 20,000 Hz.
Power
Requirements: 120 volts, 50/60 Hz, 30 watts
Transistor
Complement:
2 - JFET
3 - MOSFET
30 - Silicon Planar
31 - Diodes
2 - Integrated Circuits (each contains the
equivalent of 16 transistors and 8 diodes)
Mechanical
SIZE:
Front panel
: 16 inches wide (40.64 cm) by 5-7/16
inches high (13.81 cm);
Chassis
: 15 inches wide (38.1 cm) by 13 inches
deep (33.02 cm), including PANLOC shelf and back panel connectors;
Knob
Clearance : 1½
inches (3.81 cm) in front of mounting panel.
WEIGHT: 26 pounds (11.79 kg) net, 38 pounds (17.24
kg) in shipping carton.
FINISH: Front panel: Anodized gold and black with
special gold/teal panel nomenclature illumination.
CHASSIS: Chrome and black.
MOUNTING: Mclntosh developed professional PANLOC
Features & Facilities
Volume
Control: Precision "tracked" at al l listening levels. (0 to —65
dB). Does not change stereo balance as loudness is changed. The AC power ON/OFF
switch is coupled with this control.
Balance
Control: Natural balance at center position, attenuation of left or right
channel by rotating control.
Loudness: Loudness compensated or flat
response—Loud- ness position
boosts low frequencies for low level listening. Operates as a function of
volume control position. Full compensation is obtained at lower volume levels
and flat response is obtained at full volume.
Selectivity: Increases
the ability of the tuner to separate a weak (distant) station from a strong
(local) station on adjacent channels.
Mode: Selects
either stereo or mono operation
Phase
Control: Electronically reverses phase in the left channel to correct
"out of phase" program sources. MUTING: Suppresses the background
noise and hiss normally heard between FM stations.
Tape
Monitor: Pushbutton; compares recorded tape with program source while
recording.
Muting
Adjust: Modifies the noise rejection threshold on
FM Dial Scale Intensity: Modifies the brightness of the illumination of the front
panel