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WARNING: TO PREVENT FIRE OR SHOCK
HAZARD, DO NOT EXPOSE THIS UNIT TO
RAIN OR MOISTURE.
The Mclntosh you have purchased has a serial number located on
the rear panel of the chassis.
Record that serial number here
for future references. The model and serial number are important
to you for any future service.
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Your C 32 Stereo Preamplifier will
give you many years of pleasant and
satisfactory performance. If you
have any questions, 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 Service...
Fill in the Application NOW.
Contents
INTRODUCTION 2
HOW TO INSTALL 2
HOW TO CONNECT 4
USING THE FRONT PANEL CONTROLS 8
USING THE PUSHBUTTONS 11
BALANCING YOUR STEREO 12
LISTENING TO YOUR STEREO 12
PERFORMANCE LIMITS AND RATINGS 13
PERFORMANCE CHARTS 14, 15
TECHNICAL DESCRIPTION 16
BLOCK DIAGRAM 19
THREE YEAR SERVICE CONTRACT
An application for a FREE THREE YEAR SERVICE CONTRACT is included with this manual.
The terms of the contract are:
1. Mclntosh will provide all parts, materials and
labor needed to return the measured perfor-
mance of the instrument to the original per-
formance 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 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 un-
authorized repair the SERVICE CONTRACT
will be cancelled. Damage by improper use or
mishandling is not covered by the SERVICE
CONTRACT.
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. For your protection Mclntosh selects only
dealers who have technical competence to
guide purchasers fairly, and provide service
when necessary. To receive the SERVICE
CONTRACT your purchase must be made
from a Mclntosh franchised dealer.
6. Your completely filled in application for a
SERVICE CONTRACT must be postmarked
within 30 days of the date of purchase of the
instrument.
7. To receive the SERVICE CONTRACT all in-
formation on the application must be filled
in. The SERVICE CONTRACT will be issued
when the completely filled in application is
received at Mclntosh Laboratory Incorporated
in Binghamton, New York.
Copyright © 1977 by Mclntosh Laboratory Inc.
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gain and differences in input level.
The C 32 uses active circuitry, electrically independent
of the volume control. Close conformity to Fletcher Munson
Equal Loudness Curves is attained regardless of volume
control position.
Active Filter Circuitry
Loudness, equalizer, and band pass filters of the C 32
are all constructed with ion implanted junction field effect
operational amplifiers (popularly called "Op Amps").
These new devices amplify with a 6 dB better signal to
noise ratio than bipolar input op amps.
Program Equalizers
To adjust for program limitations and personal prefer-
ences the C 32 LISTEN program line has a five band boost/
cut program EQUALIZER based on resonant circuit opera-
tional amplifier. The preamplifier is flat when the EQUAL-
IZER controls are at the 12 o'clock position. EQUALIZER
center frequencies of 30, 150, 500, 1500 and 10,000 Hz
were chosen to cover the audio spectrum in approximately
equal two octave bandwidths. Maximum boost and cut is
12 dB at band centers.
HF and LF Filters
The HF and LF filters are selected by pushbutton switches
in a manner electrically similar to the program EQUALIZERS
and are pushbutton switch selected. The HF filter attenu-
ates all frequencies above 5 kHz, reaching a rate of 12 dB
per octave, at 7 kHz (at which point attenuation is 3 dB
below the 5 kHz level). The LF filter attenuates all fre-
quencies below 50 Hz, at a rate of 12 dB per octave.
All program EQUALIZERS and HF/LF filters are bypassed
when the EQ OUT pushbutton switch is depressed. The
EQ OUT switch also removes subsonic and supersonic fil-
ters below 20 Hz and above 20,000 Hz, extending total
frequency response to 10 Hz to 100,000 Hz.
The Expander
To overcome the compression imposed in radio broad-
casting and recording, and to reduce hum, scratch and hiss,
the C 32 has a logarithmic program expander in the
LISTEN program line. Controls are provided to adjust the
operating point, attack time and expansion ratio.
Signal from the equalizer circuit is applied to a voltage
controlled amplifier (VCA) which operates as a variable
gain block. Control voltages for this VCA are developed
from a sample taken from the output of the equalizer. The
electronic processing of this sample is detailed. It includes
band shaping, logarithmic amplification, full wave rectifi-
cation, level setting, expansion ratio regulation, attack
timing, level setting and DC amplification. The resulting
voltage controls the gain of the VCA to cause logarithmic
gain reduction below set level and logarithmic expansion
above set level.
A switched bypass link provides a program path around
the expander, to maintain a constant signal level with the
expander in or out of the circuit. The gain of the amplifier
block incorporated in the link approximates the gain of
the expander circuit.
The Record Program Line
The C 32 is designed to permit simultaneous recording
on up to three tape recorders of any program input selected
on the RECORD switch regardless of what is being heard
on the LISTEN program line. The RECORD switch selects
its input from the same inputs, but entirely independently
from the LISTEN switch. As this selection is by means of
high impedance FET Analog switches, switching to or over
an input in use on the LISTEN program line does not cause
any audio interference.
Output from the RECORD switch is fed through tape
interlock switches to the three pairs of tape recorder output
jacks. In the event that one of the tape recorders is chosen
as an input signal to the RECORD program line, its asso-
ciated tape interlock is opened to prevent feedback through
that tape recorder back into the C 32 input.
Monitor Amplifier/Headphone Circuits
The C 32 contains a stereo power amplifier which pro-
vides adequate power to drive electrostatic headphones.
The upper HEADPHONE output jack is connected directly
to this MONITOR AMPLIFIER output, making the full 12
watts per channel power available to drive those head-
phones which require it. The lower HEADPHONE jack is
fed through a network designed to match low impedance
dynamic headphones.
In addition, the MONITOR AMPLIFIER may be switched
to either program line, controlled and connected with
enough flexibility that several other uses for it are possible.
Some of these are:
1. As a preamplifier/power amplifier in a completely
separate stereo system.
2. To power rear channel speakers when used in a 4-
channel discreet system.
3. To operate speakers in another area.
4. To feed a 600 ohm line.
On the rear panel are two green AC power outlets and
a slide switch marked AUTO/MANUAL. Plug the AC power
cables from the turntable into the green TURNTABLE
POWER outlets on the rear panel. When the switch is in
the AUTO position, power to the black AC power outlets,
can be controlled by the front panel POWER switch or
by the current drawn by a turntable plugged into the
green TURNTABLE POWER outlets. The current sensing
green AC power outlets will control the AC power to the
entire system from the AC power on/off switch on the
turntable. When the turntable is turned off with its own
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