McIntosh MPI-4 Owners manual
THE MclNTOSH MPI 4 MAXIMUM PERFORMANCE INDICATOR
Reading Time 40 Minutes
Price $1.25
Your MPI 4 Maximum Performance
Indicator will give you many years of
pleasant and satisfactory performance.
If you have any questions concerning the
operation or maintenance of this
instrument, please contact:
CUSTOMER SERVICE
Mclntosh Laboratory Inc.
2 Chambers Street
Binghamton, New York 13903
Phone: 607-723-3512
Take Advantage of 3 years
of FREE Factory Service . . .
Fill in the Application NOW.
contents
GUARANTEE ... 1
GENERAL ... 2
INSTALLATION ... 2, 3
HOW TO CONNECT . . . 3-5
FRONT PANEL INFORMATION ... 6-8
LEVEL SET PANEL INFORMATION ... 8
REAR PANEL INFORMATION ... 9
INITIAL SETUP ... 9, 10
HOW TO USE THE MPI 4 ...
PERFORMANCE LIMITS ... 18, 19
TECHNICAL DESCRIPTION ... 19, 20
BLOCK DIAGRAM ... 21
10-18
Guarantee
Mclntosh Laboratory Incorporated guarantees this instrument
to be capable of performance as advertised. We also guarantee
the mechanical and electrical workmanship and components to
be free of defects for a period of 90 days from date of purchase.
If such defects occur, Mclntosh Laboratory or one of its authorized
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:
For Three Years from date of purchase—
1. Mclntosh 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.
2. Any Mclntosh authorized service agency will repair all Mclntosh 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.
3. Always have service done by a Mclntosh 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.
agencies will repair the defect at no cost to the purchaser. This
guarantee does not extend to components damaged by improper
use nor does it extend to transportation to and from the factory
or service agency.
4. 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.
5. The SERVICE CONTRACT is given to purchasers who live
in the 50 United States or Canada only.
6. For your protection Mclntosh selects its dealers carefully.
Only one dealer in ten qualifies for a Mclntosh franchise,
To receive the SERVICE CONTRACT your purchase must be
made from a Mclntosh franchised dealer.
7. Your completely filled in application for a SERVICE CON-
TRACT must be postmarked within 30 days of the date of
purchase of the instrument.
8. 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 re-
ceived at Mclntosh Laboratory Incorporated in Binghamton,
New York, If the application is not received at Mclntosh
Laboratory, only the service offered under the 90-day guarantee will apply.
Copyright © 1973 By Mclntosh Laboratory Inc.
1
General
installation
The MPI 4 is a laboratory-grade instrument. It provides
the facility to continuously monitor the quality of the performance of a stereo system. The MPI 4 can sample and dis-
play signals from the tuner, preamplifier and power amplifier without reconnecting cables. Signals are displayes on an
oscilloscope screen calibrated with scales for tuning,
measuring and testing.
As a tuning aid, the instrument is a guide to exact FM
station selection and precise tuning. The screen displays
FM signal strength, modulation percentage and mulitpath
interference. Audio signals may be viewed for stereo balance, strength, phase and channel separation. Output power
of the power amplifier can be seen at any instant during
program performance, or stored to develop a trend over
several minutes.
With the addition of test records, the MPI 4 can show
compliance and trackability of a phono pickup, frequency
response of the preamplifier and power amplifier, audio
distortion and stereo speaker balance.
In one of its operational modes, the MPI 4 becomes a
"dual trace" oscilloscope. When operated in the dual trace
mode the left and right stereo channels appear simul-
taneously and separately on the screen for direct comparison. The instrument also has "triggered sweep." It permits
the viewer to choose a single tone and lock it on the screen
for careful inspection.
In a search for convenient equipment-mounting tech-
nique, Mclntosh developed the PANLOC system. Pressing
the two PANLOC buttons on the front panel of the MPI 4
releases the unit to slide in or out of its mounting. This
allows easy access to cable connections at the rear. It
brings top panel controls into view for easy adjustments,
adjustments.
Ventilation extends the trouble-free life of an instru-
ment by preventing excessive internal temperature and
insulation breakdown. To accomplish this, allow cool air
to enter at the bottom of the instrument and warm air to
escape at the top. The MPI 4 Maximum Performance Indicator may be mounted in any position. It requires a
mounting space 15 inches deep (38.1 cm), 17½ inches
wide (44.45 cm), and 6 inches high (15.24 cm).
To mount in the Mclntosh cabinet follow the instructions enclosed with the cabinet. For any other installation,
remove the instrument, PANLOC brackets, parts bag and
mounting template from the carton. Remove the MPI 4
from the plastic bag and place it upside down on the
shipping pallet. Then remove the four plastic feet fastened
to the bottom of the chassis.
1. POSITION TEMPLATE AND MARK
Position the plastic mounting template over the area of
the cabinet panel where the MPI 4 is to be installed.
Be sure that the edges of the equipment marked on the
template clears any shelves, partitions or existing
equipment located behind the panel. With the template
in place mark the six "A" and "B" holes and four smalt
holes locating the corners of the cutout. Next, join the
four corner marks with pencil lines. The edge of the
template is used as a straight edge.
2. DRILL HOLES
With the drill perpendicular to the panel, drill the
six "A" and "B" holes using a 3/16 inch drill. THE
SIX HOLES MUST BE DRILLED BEFORE MAKING
THE CUTOUT.
2
3. SAW CUTOUT
Carefully cut the rectangular opening on the inside of
the pencilled rectangle.
How to connect
4. SECURE MOUNTING STRIPS
Install the mounting strips (supplied in the hardware
package) on the inside of the cabinet panel. Insert
two screws (supplied in the hardware package) into
the center holes ("B" holes on the template). Use the
¾-inch long screws for panels under ½-inch thick or
1¼-inch screws for panels ½-inch thick or over. Place
a mounting strip on the back of the cabinet panel.
Align it with the three holes in the panel and tighten
the screw. The screw head should pull slightly into the
wood panel. Attach the other mounting strip by repeating the procedure.
5. MOUNT THE PANLOC BRACKETS
Attach the PANLOC brackets to the cabinet panel
using four screws of the proper length. Place the template over the mounting screws. The screws should
be centered on the "A" and "B" holes in the template.
If necessary, loosen the screws and push the mounting
brackets into alignment then retighten.
6. INSTALL THE UNIT
Thread the power cord through the opening in the
cabinet panel. Carefully slide the instrument into the
opening so the rails on the bottom of the instrument
engage the track on the mounting brackets. Slide the
instrument in until it stops at the ad|ust position
latches. Press the latches in and continue to slide the
instrument until its front panel is flush with the cabi-
net panel. At the bottom front corners are the PANLOC
buttons. Depressing the PANLOC buttons will lock the
instrument firmly in the cabinet panel. Pressing the
PANLOC buttons a second time will release the instru-
ment You can then slide the instrument forward to the
adjust position. Pressing the adjust position latches
will allow the instrument to be removed from the
cabinet.
The MPI 4 may be connected to a stereo receiver (Fig.
1) or to a component system with a separate preamplifier and power amplifier (Fig. 2). Choose which most
closely resembles your system.
AUDIO INPUTS
Low Level Audio Input
Use one of the 6-foot shielded cables supplied, to connect the left channel output on your preamplifier to the
LEFT AUDIO INPUT on the MPI 4 back panel. Similarly,
connect the right channel preamplifier output to the
RIGHT AUDIO INPUT.
SPEAKER INPUT
There are four color-coded push connectors on the back
panel of the MPI 4. Connect these with two pairs of speaker
cables to the left and right output on the power amplifier.
Black Left speaker common terminal
Green Left speaker high terminal
White Right speaker common terminal
Red Right speaker high terminal
Set the SPEAKER IMPEDANCE switch on the MPI 4 back
panel to agree with the speaker system impedance: 4W,
8W, or
16W.
TUNER INPUTS
Signal Strength Input
Mclntosh tuners and receivers provide signal for the
SIGNAL STRENGTH INPUT at a connector marked TP 1
on the back of each tuner. Using the 3-foot low-capacity
shielded cable supplied, connect the TP 1 output to the
SIGNAL STRENGTH INPUT.
TO PREVENT HIGH FREQUENCY LOSSES, THE SPECIAL
3-FOOT CABLES SUPPLIED MUST BE USED. DO NOT
SUBSTITUTE ORDINARY AUDIO CABLE.
For other tuners or receivers which do not provide a
signal strength output, consult the manufacturer or their
authorized service agency.
Deviation Input
Mclntosh tuners and receivers provide signal for the
DEVIATION INPUT at a connector marked TP 2 on the back
of each tuner. Using the 3-foot low-capacity shielded
cable supplied, connect the TP 2 output to the DEVIATION INPUT.
TO PREVENT HIGH FREQUENCY LOSSES, THE SPECIAL
3-FOOT CABLES SUPPLIED MUST BE USED. DO NOT
SUBSTITUTE ORDINARY AUDIO CABLE.
For tuners or receivers which do not provide a deviation output, consult the manufacture or their authorized
service agency.
3
HOW to Connect
FIG. 1 CONNECTING THE MPI 4 TO STEREO RECEIVER
(TYPICAL CONNECTIONS)
STEREO RECEIVER
AC CORD
ENVIRONMENTAL
EQUALIZER. IF
USED
BLACK
GREEN
RED
WHITE
4
FIG. 2. CONNECTING MPI 4 TO COMPONENT SYSTEM
(TYPICAL CONNECTIONS)
STEREO FM TUNER
LEFT
SPEAKER
ENVIRONMENTAL
EQUALIZER
(OPTIONAL)
RIGHT
SPEAKER
5
Front Panel information
FIG. 3 FRONT PANEL
MODE SELECTOR
The MODE SELECTOR pushbuttons select the type of
display seen on the screen of the MPI 4. Each of the five
pushbuttons selects a trace—a glowing line of green light—
which shows a variety of information about signals from
the tuner, preamplifier or power amplifier. To assist the
evaluation of each display, the reticle in front of the
screen is marked with calibration points which are used to
measure signal characteristics. As MODE SELECTOR
buttons are pressed, the screen reticle is illuminated in
these colors:
Mode Color
Multipath Blue
Stereo Red
Level Amber
Sweep Green
MULTIPATH
When properly connected to an FM tuner the MPI 4
will detect and display multipart reception. Multipart
reception is the result of a reflected signal arriving at the
tuner antenna slightly later than the direct signal. By
rotating or repositioning the FM antenna it is possible to
reduce multipath reception. The MPI 4 makes it easy to
know when the FM antenna is oriented for the best reception of any station.
To show multipart reception the MPI 4 displays instantaneous signal strength versus frequency deviation.
Signal strength is shown as vertical deflection of the indicator display beam. Frequency deviation is shown as
horizontal deflection. Multipath reception appears as a
peak or valley in the display.
Multipath reception degrades FM tuner performance in
several ways:
1. Usually there is an increase in background noise
level.
2. Distortion is often heard in the program signal
3. Stereo separation may be reduced.
4. The stereo effect may be completely lost.
5. Stereo indicators may fail to function, or function
erratically.
To overcome multipart reception it is usually necessary
to turn the antenna to receive the FM signal by one predominant path. Rotating a directional antenna is effective
at correcting multipath reception. In areas where a simple
antenna such as a dipole is used repositioning the antenna
can achieve similar results.
In the MULTIPATH mode the MPI 4 is a very effective
tuning indicator:
1. Signal strength is shown by the vertical position of
the display trace. The higher the position of the
trace the greater the signal strength.
2. Correct tuning occurs when the display trace is
centered horizontally on the screen. Since the display trace effectively follows the tuner IF response
curve, centering the trace tunes the detector to
the center of the IF curve.
The display of the signal, when there is no multipath
reception affecting the program, appears as a smooth
curving line, (Fig. 4). The calibration points are the two
100% marks at the bottom of the screen. As the program
material grows louder or softer, the trace expands and
contracts. The 100% points indicate the highest modulation percentage normally transmitted by an FM station.
(A more detailed description appears in the "How to Use
Section.")
STEREO
A stereo program causes a complex display which
varies between a circular shape and an elliptical shape.
A mono program causes the display to be a slanted line.
With an in-phase mono program, the signal falls between
the L + R boundaries; in out-of-phase mono program the
trace falls along the L — R boundaries.
6
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