McIntosh MX-110 Owners manual

STEREO TUNER

PREAMPLIFIER

CONTENTS

MX 11O

GENERAL DESCRIPTION 1
TECHNICAL DESCRIPTION 1
FRONT PANEL FACILITIES 5

INSTALLATION 10

CONNECTING 10

AC Connections 10
AC Power Connection 10

Input Connections 11
Output Connections 12
Antenna Connections 12

OPERATING INSTRUCTIONS 13

Balancing a Stereo System 13

Adjusting Phase 14

Balancing Loudness Between

Program Sources 14

Adjusting the Balance Control After the

System has been Balanced 15

Adjusting for Special Effects 15

Listening to Monophonic FM Program 15
Listening to MPX Stereo 16
Listening to a Stereo Record 16
Listening to Monophonic Records 16

Listening to Tape Decks 16

Listening to Stereo Tape Machine 17
Operating Curves 18

GUARANTEE 20

OWNER'S MANUAL

MX11O

MX110 TUNER PREAMPLIFIER

GENERAL DESCRIPTION

The MX110 combines in one unit an ex-

tremely low-distortion preamplifier with a

highly sensitive FM multiplex stereo tuner.

Every desirable feature of a tuner and a pre­amplifier is included in this design. Inter­station noise suppression, tuning indicator,

FM multiplex indicator, individual channel
bass controls, individual channel treble con­trols, electronic phase switch have all been
engineered into the MX110. The INPUT
SELECTOR gives you a choice of six different

program sources. The MODE SELECTOR is a

newly developed control which makes it very
easy to balance a stereo system. It is de­signed to add left to right for monophonic
operation, to control the left to right stereo

perspective or to compare the left and right
channels of a stereo program. The loudness
of the phono channels and the auxiliary
channel may be balanced to the tuner loud-

TECHNICAL DESCRIPTION

The radio-frequency amplifier of the
MX110 is a "cascode" type circuit. The cir­cuit is specially designed to amplify weak
signals with less noise and distortion. By
carefully tuning this RF amplifier during
manufacturing and controlling other circuit

constants, spurious response rejection is

improved. The high-frequency oscillator me-

chanical layout is engineered for minimum

response to temperature variations. In fact

the combination of mechanical and elec­tronic design is so unusually good in this
circuit that automatic frequency control is

not needed in the MX110. The mixer output
is amplified by four flat-topped intermediate

frequency amplifiers. The transformers used

in the LF. amplifiers are designed for maxi­mum adjacent channel rejection, for electri-

cal stability, and for electrical and mechanical

resistance to shock and vibration.

ness. These adjusting controls are located on

the top of the MX110 behind the front panel.

By releasing the PANLOC buttons on the

front panel, you can slide the MX110 out of

its mounting until the second latch engages.

The top mounted LEVEL set controls are

now available.

The Mclntosh designed PANLOC system

is the first professional installation technique

to be used on stereo instruments. The

PANLOC system gives you absolute ease of
installation, operation, and maintenance.

The Mclntosh MX110 is a beautifully
engineered control center for the finest
stereo sound systems. The extreme care in

manufacturing, in layout design and in ther­mal engineering promises the usual Mclntosh
extra values of reliability, performance, and
long life.

The R.F. and I.F. circuits of the MX110 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 MX110. A VHF
television antenna which is suitable for FM

reception can be connected to the MX110.

In the MX110, a new type of mechani­cal tuning assembly gives smooth flywheel
tuning. By controlling the relations between
mass and mechanical resistance, and divid­ing work loads 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 smooth, quiet
action and extended life with virtually no
wear, a teflon lined dial pointer carriage and
nylon pulleys are used in the dial cord as­sembly.

1

MULTIPLEX DECODER

The multiplex decoder uses a special

Mclntosh developed detecting circuit. One of
the advantages of this circuit is the elimina­tion of the critical adjustments necessary
with commonly used matrixing methods. This
circuit detects the L+R sidebands and auto-

matically matrixes the recovered informa­tion with the L+R main carrier signal. This
circuit then yields the left and the right

program with maximum separation.

A temperature stabilized 19KC amplifier
locks-in a highly stable push-pull synchro­nous oscillator. Apart from other advantages,

this method provides greatest noise immu-

nity. Balanced detectors cancel 19KC and

The MX110 audio amplifier consists of
three negative-feedback amplifying sections
in duplicate for the left and right stereo chan-

nels and a separate L+R monophonic ampli­fier. The first section in each channel is a
feedback preamplifier used to amplify and
compensate for the input signals coming
from phonograph pickups or tape heads.

Level set controls are connected into the out-

put circuit of this preamplifier section when
the INPUT SELECTOR is switched to PHONO

1 or PHONO 2. These controls may be used
to maintain uniform loudness between phono
and tuner inputs. Skillful layout, grounding,
and shielding for low-hum pickup, metal film

resistors, low-noise tubes and extreme care
in manufacturing combine to reduce noise
and hum in the input amplifiers.

The second amplifier section in each chan-

nel is a cathode follower. The sharp cut-off

38KC components in the output and insure
low distortion.

A three-section sharp cut off filter rejects
SCA interference and reduces susceptibility
to spurious signals.

The MX110 has an MPX stereo indicator
that lights when the dial pointer crosses a
station broadcasting MPX stereo. A unique
circuit using a transistor operates the MPX
stereo indicator. The transistor is controlled
by a differential detecting circuit that am­plifies the 19KC pilot signal. This circuit auto­matically discriminates between the 19KC
signal and noise.

AUDIO

(18db per octave) rumble and high-frequency
filters are associated with this section. Input­level set controls for the auxiliary inputs are

associated with this section. All the level set

controls are conveniently accessible

The third amplifier section is a two stage
negative feedback amplifier. The variable
bass and treble controls are included in the

feedback loop to maintain the lowest possible

distortion. For example a wave meter analy­sis of the three amplifier sections of the
MX110 shows less than 1/10 of 1% dis-

tortion at 3 volts output. The MODE SELEC­TOR, balance controls and left and right out-

puts are associated with the third amplifier
section.

The L+R monophonic amplifying section
is a feedback summing amplifier. It supplies
monophonic output as well as L+R output.

POWER SUPPLY

The power supply of the MX110 has re­ceived very special design attention. Three
separate rectifier circuits are used.

First, a full-wave rectifier supplies D.C. to

the heaters of all audio stages.

A second bridge rectifier supplies D.C. to
the anodes of the audio stages.

Then a third full-wave rectifier supplies

2

D.C. to the tuner stages.

This elaborate power supply design in­sures the lowest possible background hum
level and also the maximum stability. In
addition to this careful work the power trans­former uses special magnetic shielding to
minimize possible hum pickup in the MX110
as well as in any other equipment used with it.

MECHANICAL SPECIFICATIONS

Dimensions

Chassis: 16 inches wide; 57/16 inches high;

13 inches deep including connectors.
Front Panel: 16 inches wide; 57/16 inches high.
Knob Clearance: 1½ inches.

Weight

Chassis: 27½ pounds.
Shipping Weight: 36 pounds.

TUNER SPECIFICATIONS

Sensitivity

Better than 2.5 microvolts at 100% modula-

tion.

R.F. Amplifier

Cascode.

LF. Amplifiers

Four.

Limiters

Two.

LF. Bandwidth

200KC flat top.

Finish

Anodized gold and black (front panel).

Installation

Convenient, professional PANLOC.

Frequency Response

Within ± 1db 20 to 20,000 cycles. (Including

75 microseconds deemphasis.)

Hum

Greater than 70db or more below 100%

mod. (Audio tubes have D.C. on the fila­ments.)

Drift

Less than 25 KC.

Ant. Input Impedance

300 balanced, 75 ohms unbalanced.

LF. Transformers

Mechanically captive.

Muting

LF. injected.

Tuning Indicator

Tuning is indicated by an electron ray tube.

MULTIPLEX DECODER SPECIFICATIONS

MPX Decoder

Hum Level: Better than 60db below 100%

stereo modulation.

Distortion: Less than 0.3% (Multiplex De-

coder only).

Channel Separation: Better than 30db at

1000 cps.

AUDIO SPECIFICATIONS

Inputs

Total 5 each channel:

AUX.;

PHONO 1 MAG. or XTAL;

PHONO 2 MAG.;
TAPE HEAD;
TAPE MONITOR.

Radiation

Substantially below F.C.C. requirements.

Distortion

Less than 0.6% distortion at 100% modula-

tion, ± 75KC deviation above 2.5 micro-

volts at antenna.

Suppression of Pilot (19KC), and Carrier

(38KC): Greater than 40db below 100%
modulation.

Front Panel Stereo Indicator Light: Acti-

vated by 19KC pilot carrier only.

Outputs

Main Stereo Outputs, 1 Tape Stereo Output,

1 L+R Output.

AC AUX

Outlets

1 unswitched, 2 switched.

3

Controls

Input Selector: Total 6 positions: AUX,

MPX, FM, PHONO 1, PHONO 2, TAPE
HEADS.

Mode Selector: Total 7 positions: L TO L&R,

R TO L&R, STEREO REV., STEREO, MONO,

L+R TO L, L+R TO R.

Tone: Dual treble and bass negative-feed-

back controls with slip clutch for independ-

ent adjustment of each channel. Bass

Boost: 15db at 50 cycles. Bass Cut: 18db

at 50 cycles. Treble Boost: 15db at 10,000
cycles. Treble Cut: 15db at 10,000 cycles.

Balance: Turn to right to emphasize the

right channel. Turn to the left to emphasize
the left channel.

Phase: 2 positions: NORMAL or REVERSED:

Changing phase does not increase distor-

tion. H.F. Cutoff Filter: 2 positions: Flat, or

5KC cutoff. (20db per octave.) L.F. Cutoff
Filter: 2 positions: Flat, or 50 cycles cutoff.
(20db per octave.)

Loudness: Fletcher Munson compensation.

Tape Monitor: 2 positions: IN and OUT. For

comparison of recorded tape with program
source after recording.

Tuning: Flywheel tuning—no backlash.

Muting: 2 positions: IN or OUT for intersta-

tion noise suppression.

Level Set: Three left and three right controls.

2 for AUX, 2 for PHONO 1, and 2 for

PHONO 2. These controls are located back

of the front panel on the top of the MX110.

AC Power—Concentric with BALANCE con-

trol: ON-OFF.

ELECTRICAL

Frequency Response

±½db 20 to 20,000 cycles.

Distortion

Less than 0.2% at rated output.

Hum and Noise

High-level inputs: 80db below rated output.

Low-level inputs: less than 3 microvolts at
input terminals.

Input Sensitivity

AUX: 0.3 volt at 200K.

PHONO 1:3 millivolts at 47K.

PHONO 2: 3 millivolts at 47K.

TUBE COMPLEMENT

1 6DS4 R.F. -1 amplifier (nuvistor)
1 12AT7 R.F.-2 mixer
1 6AB4 Oscillator
1 6AU6 IF-1
1 6AU6 IF-2
1 6AU6 lF-3/Limiter 1

1 6CS6 IF-4/Limiter2

1 12AT7 Muting/L+R Amplifier

1 6HU6/EM87 Tuning Indicator

1 6D10 FM AUDIO/Left and Right

1st Audio Amplifier

1 6U8 MPX Amplifier and 19KC

Separator/Indicator control

SPECIFICATIONS

TAPE HEAD: 3 millivolts at 220K.
TAPE MONITOR: 0.3 volt at 100K.

Outputs

MAIN: 3 volts 2 in parallel each channel.
L+R: 3 volts.

TAPE: From FM at 100% modulation 0.9

volt from PHONO when cartridge output

is 9.0 millivolts—0.9 volt; with rated input

—0.3 volt.

POWER REQUIREMENTS: 105-125 volts AC

50/60 cycles; 75 watts.

FUSE: 1 amp. Slo-Blo.

1 12AU7
1 12AX7
1 12AX7

1 12AX7

1 6U8
1 6U8

2 Diodes

1 Diode

1 Diode
4 Diodes
2 Diodes

MPX 38KC Oscillator

Phono Preamplifier Left
Phono Preamplifier Right

Left and Right 2nd Audio
Amplifier
Left 3rd Audio Amplifier
Right 3rd Audio Amplifier
Discriminator
Muting and Tuning Eye
Detectors
AGC Clamp

Balanced MPX Detectors
Balanced Det. for Indicator

Light

4

2 Silicon

Diodes

1

MA113

DC Filament Supply
Transistor-Indicator Light
Switch

FRONT PANEL INFORMATION

4 Selenium

Rectifiers

High and Low Voltage Supply

Figure 1. MX110 Front Panel.

DIAL SCALES

The MX110 has two scales. The 88 to 108
scale is marked in megacycles. The 0 to 100
scale is the logging scale. The logging scale

can be used to accurately retune any station.
You may find it easier to keep a record of
your favorite stations by use of the logging

scale.

INDICATORS

The MX110 has two indicators. They are

just below each end of the logging scale. On
the right end is the MPX STEREO indicator.
On the left end is the tuning indicator.

Figure 2. MPX Stereo Indicator.

The MPX STEREO indicator will light up if

the dial pointer crosses a station broadcast-

ing MPX stereo. A special circuit is used to

operate this panel indicator. This circuit
automatically detects the 19KC MPX stereo

signal while rejecting noise pulses of equal
intensity. For listening to MPX stereo, refer to
OPERATING INSTRUCTIONS on page 00.

The tuning indicator off tune.

The tuning indicator on tune.

Figure 3. Tuning Indicator.

The tuning indicator uses the movement
of two electron beams inside a vacuum tube
to show when a station is precisely tuned.

The beams move toward each other as the
station comes into tune. The station is pre­cisely tuned when the beams come closest

together. The action of this indicator is sub­stantially independent of the signal strength
of the station. Only the very weakest signals
will not close the beams.

5

VOLUME

Figure 4. VOLUME Control.

The VOLUME control is the large knob
located to the left side of the dial face. The
volume control adjusts the loudness of both
stereo channels and also the L+R mono­phonic channel.

INPUT SELECTOR

Figure 5. INPUT SELECTOR.

1. AUX—The AUX position of the INPUT

SELECTOR connects the back panel jacks
marked AUX through the MX110. Use these

jacks to connect any high level program

source through the MX 110. Connections are
made following the instructions on page 11 in
the section titled CONNECTING. Operating

procedure is on page 13 in the section
titled OPERATING INSTRUCTIONS.

2. MPX—The MPX position of the INPUT

SELECTOR connects the multiplex decoder

to the output jacks of the MX110. Listen to

MPX stereo broadcasts in this position. To

properly connect and operate the MX110,

consult the sections titled CONNECTING on

page 11 and OPERATING INSTRUCTIONS

on page 13.

3. FM—The FM position of the INPUT SELEC­TOR connects FM monophonic programs to

the output jack of the MX110. To properly
operate the MX 110, consult the section
titled OPERATING INSTRUCTIONS on page

13,

4. PHONO 1—The PHONO 1 position of the
INPUT SELECTOR connects the jacks on the
back panel marked PH-1 MAG. and PH-1

XTAL through the MX110. Any stereophonic
or monophonic magnetic phono cartridge

plugged into the PH-1 MAG. jacks is fed

through the MX110. Any constant ampli­tude cartridge such as a crystal or ceramic
device plugged into the PH-1 XTAL jacks is
fed through the MX110. To properly connect
and operate the MX110 for use with phono
cartridges, see the sections titled CON-

NECTING on page 11 and OPERATING

INSTRUCTIONS on page 13.

5. PHONO 2—The PHONO 2 position of the

INPUT SELECTOR connects the jacks on the

back panel marked PH-2 through the MX110.
Any magnetic phono cartridge plugged into
the PH-2 jacks is fed through the MX110. To
properly connect and operate the MX110 for

use with phono cartridges, see the sections
titled CONNECTING on page 11 and OPER­ATING INSTRUCTIONS on page 13 .

6. TAPE HD—The TAPE HD position of the

INPUT SELECTOR connects the jacks on the
back panel marked TAPE HEAD through the
MX110. A tape deck that does not contain
its own playback preamplifier is connected to
the MX110 through this position. To properly
connect and operate the MX110 for use with

tape decks, consult the sections titled CON-

NECTING on page 11 and OPERATING IN-

STRUCTIONS on page 13.

MODE SELECTOR

1. L TO L&R—The MODE SELECTOR in the

L TO L&R position connects the left input to
both amplifiers and both loudspeakers.

2. R TO L&R—The MODE SELECTOR in the
R TO L&R position connects the right input to
both amplifiers and both loudspeakers.

3. STEREO REV-The MODE SELECTOR in

the STEREO REV position connects the left

input to the right loudspeaker and right input

to the left loudspeaker.

6