THE C 29 SOLID STATE STEREO PREAMPLIFIER

THE C 29 SOLID STATE STEREO PREAMPLIFIER
THE C 29 SOLID STATE STEREO PREAMPLIFIER
Reading Time: 38 Minutes
Price: $2.00
VARIOUS REGULATORY AGENCIES REQUIRE THAT WE BRING THE FOLLOWING IN
FORMATION TO YOUR ATTENTION. PLEASE READ IT CAREFULLY.
WARNING: TO PREVENT FIRE OR SHOCK
HAZARD, DO NOT EXPOSE THIS UNIT TO
RAIN OR MOISTURE.
The Mcintosh you have purchased is a C 29
Preamplifier. It has a serial number located on the
rear panel of the chassis. Record that serial number
here:
Serial Number
The model, serial number and purchase date are important to you for any future service. Record the purchase date here:
Purchase Date
Upon application, Mcintosh Laboratory provides a
Three-Year
Service
Contract.
Your
Mcintosh
authorized Service Agency can expedite repairs
when you provide the Service Contract with the instrument for repair. To assist, record your Service
Contract number here:
Service Contract Number
Your C 29 Preamplifier will
give you many years of pleasant and
satisfactory performance. If you
have any questions, please contact:
Contents
CUSTOMER SERVICE
Mcintosh Laboratory Inc.
2 Chambers Street
Binghamton, New York 13903
Phone: 607-723-3512
HOW TO INSTALL... 2
HOW TO CONNECT... 4
THE FRONT PANEL CONTROLS
AND HOW TO USE THEM .. .8
TOP PANEL CONTROLS .. .11
SPECIFICATIONS... 12
FACILITIES AND FEATURES .. .13
TECHNICAL DESCRIPTION .. .14
PERFORMANCE CHARTS .. .15
BLOCK DIAGRAM... 17
Take Advantage of 3 years
of Contract Service . . .
Fill in the Application NOW.
MCINTOSH THREE YEAR SERVICE CONTRACT
An application for a THREE YEAR SERVICE CONTRACT is included with this manual.
The terms of the contract are:
ing 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 Mcintosh 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 Mcintosh franchised dealer.
6. Your completely filled in application for
SERVICE CONTRACT must be postmarked within 30 days of the date of
purchase of the instrument.
7. 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 received at Mcintosh
Laboratory Incorporated in Binghamton, New York.
1. M c i n t o s h w i l l provide all parts,
materials and labor needed to return the
measured performance of the instrument to the original performance limits.
The SERVICE CONTRACT does not
cover any shipping costs to and from
the authorized service agency or the
factory.
2. Any Mcintosh authorized service agency will repair Mcintosh instruments at
normal service rates. To receive service
under the terms of the SERVICE CONTRACT, the SERVICE CONTRACT CERTIFICATE must be presented when the
instrument is taken to the service agency.
3. Always have service done by a Mcintosh 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 mishandl-
Copyright 1979 © by Mcintosh Laboratory Inc.
1
that cool air can enter at the bottom of the cabinet
and be vented from the top. With adequate ventilation the instrument can be mounted in any position.
The recommended minimum space for installation
is 15 inches (38.1 cm) deep, 17 inches (43.2 cm) wide,
and 6 inches (15.2 cm) high.
To install the instrument in a Mcintosh cabinet,
follow the instructions that are enclosed with the
cabinet. For any other type of installation follow
these instructions:
1. Open the carton and remove the PANLOC
brackets, hardware package, and mounting
template from the carton. Remove the C 29 from its
plastic bag and place it upside down on the shipping
pallet; unscrew the four plastic feet from the bottom
of the chassis.
2. Mark the cabinet panel.
Place the mounting template in the position on the
cabinet panel where the instrument is to be installed, and tape it in place. The broken lines that represent the outline of the rectangular cutout also represent the outside dimensions of the chassis. Make
sure these lines clear shelves, partitions, or any
equipment. With the template in place, first mark the
six A and B holes and the four small holes that
locate the corners of the cutout. Then, join the four
corner markings with pencil lines, using the edge of
the template as a straightedge.
The PANLOC system of installing equipment conveniently and securely is a product of Mcintosh
research. By depressing the two PANLOC buttons
on the front panel, the instrument slide can be locked firmly in place or it can be unlocked so that the
chassis can slide forward, giving you easy access to
the top and rear panels.
3. Drill Holes
Use a drill with a 3/16 inch bit held perpendicular to
the panel and drill the six A and B holes. Then, using
a drill bit slightly wider than the tip of your saw
blade, drill one hole at each of two diagonally opposite corners. The holes should barely touch the inside edge of the penciled outline. Before taking the
next step, make sure that the six A and B holes have
been drilled.
The trouble-free life of an electronic instrument is
greatly extended by providing sufficient ventilation
to prevent the buildup of high internal temperatures
that cause deterioration. Allow enough clearance so
4. Saw the Panel Cutout
Saw carefully on the inside of the penciled lines.
First make the two long cuts and then the two short
cuts. After the rectangular opening has been cut out,
2
use a file to square the corners and smooth any irregularities in the cut edges.
5. Install the Mounting Strips
In the hardware package you will find two mounting
strips, four 6-32 x 1 1/4 inch fillister head screws and
two 4-40 x 1 1/4 inch inch flat head screws. These are
long enough for any cabinet panel thickness up to
one inch.
Starting at the right-hand side of the panel, insert
a 4-40 x 1 1/4 inch flat head screw into the center
hole in the panel, marked B on the template. On the
back of the panel, align a mounting strip with the
holes in the panel and tighten the screw until the
screwhead is pulled slightly into the wood.
Repeat this procedure to attach the mounting
strip to the left side of the panel.
6. Attach the PANLOC Brackets
Using two of the 6-32 x 1 1/4 inch fillister head
screws in the A holes on each side, attach the
PANLOC brackets to the cabinet panel; the short
flange is mounted against the front (face) of the
cabinet panel. The screws pass through the
PANLOC bracket flange, the cabinet panel, and then
through the mounting strips previously mounted.
7. Install the Instrument
Guide the AC power cord through the panel opening
to the back of the cabinet; then, slide the instrument
into the opening carefully so that the rails on the
bottom of each side of the chassis engage the
tracks on the mounting brackets. Continue to slide
the instrument into the cabinet until it is stopped by
the adjust position latches. Press the latches inward. This permits the instrument to slide into the
cabinet until its front panel is flush with the cabinet
panel. Depress the PANLOC buttons at the lower left
and right corners of the instrument panel to lock the
unit firmly in the cabinet. Depressing the PANLOC
buttons again will unlock the instrument so that it
can slide forward to the adjust position. If you press
inward on the adjust position latches you can
remove the instrument from the cabinet.
3
How to Connect
Rear panel input jacks are provided for 2 stereo
high level sources (AUX 1 and AUX 2), a stereo tuner
(TUNER), 2 stereo turntables (PH 1 and PH 2), stereo
high impedance microphones (MIC), and 2 stereo
tape recorders (TAPE 1 and TAPE 2).
the shorting plugs.
CONNECTING MICROPHONES
Connect the cables from high impedance
microphones directly in the INPUT MIC Left and
Right jacks.
Rear panel output jacks are provided to feed 2
stereo tape recorders (TAPE 1 and TAPE 2), a stereo
600 ohm unbalanced line (LINE) and 2 stereo 2.5 volt
outputs (MAIN).
CONNECTING TAPE RECORDERS
To Record:
Connect a cable from the OUTPUT TAPE 1 Left
jack to the left high level input of the tape recorder.
Connect a cable from the OUTPUT TAPE 1 Right jack
to the right high level input of the tape recorder. Connect a second recorder in the same manner to the
OUTPUT TAPE 2 jacks.
Front panel jacks provide input and output
facilities for a tape recorder using the circuits of the
rear panel TAPE 2 connections. Two headphone
jacks are provided which are fed by a stereo
amplifier in the C 29.
CONNECTING AUX 1 AND AUX 2
Connect the left channel cable from any high level
source (tuner, TV set, tape recorder, etc.) to the INPUT AUX 1 left jack. Connect the right channel cable
to the INPUT AUX 1 Right jack. A second high level
source can be connected similarly to INPUT AUX 2.
To Playback/Monitor:
Connect a cable from the left channel output of a
tape recorder to the TAPE INPUT 1 Left jack. Connect a cable from the right channel output of a tape
recorder to the TAPE INPUT 1 Right jack. Connect a
second recorder in the same manner to the TAPE INPUT 2 jacks.
CONNECTING TURNTABLES
The C 29 has shorting plugs in the phono inputs.
To prevent unwanted noise remove the shorting
plugs only from input jacks that are to be used. Connect the cable from the left channel of the turntable
into the INPUT PHono 1 left jack. Connect the cable
from the right channel of the turntable into the INPUT PHono 1 Right jack. For a second turntable,
connect PHono 2 in the same way, after removing
Front Panel Tape Recorder Jacks:
Tape recorder inputs and outputs are available at
the TAPE IN-OUT jacks on the front panel just to the
left of the TAPE MONITOR pushbuttons. These
jacks make connections to TAPE 2 facilities without
having to go to the rear panel. A metal shielded 1/4
inch stereo phone plug is used. Connections are tip:
left signal, ring: right signal, and sleeve: common
ground.
4
5
AC POWER
TO TURNTABLES
CONNECTIONS FOR TUNERS, TURNTABLES, AND TAPE RECORDERS
AC POWER TO
TUNERS, TAPE
RECORDERS AND
POWER AMPLIFIERS
TUNER
FM ANTENNA
TURNTABLE 1
TAPE
RECORDER
1
TURNTABLE 2
TAPE
RECORDER
2
MICROPHONES
When a tape recorder is plugged into the front
jacks all the facilities normally associated with
TAPE 2 on the rear panel are automatically transferred to the front panel jacks.
The green AC power outlets are on at all times.
Plug the AC power cables from the turntable into the
green TURNTABLE power outlets on the rear panel.
The black outlets are switched on and off when the
preamplifier is turned on or off. These are intended
for power amplifiers, equalizers and other accessories up to 600 watts total capacity.
CONNECTING TO POWER AMPLIFIERS
Connect the jacks labeled "OUTPUTS MAIN" to
the input of a stereo power amplifier. The Left MAIN
jack is connected to the left amplifier input jack. The
Right MAIN jack is connected to the right amplifier
input jack.
The POWER ON pushbutton shares AC power
control with the AC power switch on a turntable,
through a current detecting switch circuit. On the
rear panel the TURNTABLE AUTO/MANUAL switch
selects the mode of operation. When the switch is in
the AUTO position and a turntable is plugged into
one of the green AC power outlets, the AC power to
the preamplifier and to the black AC power outlets
can be controlled by the turntable on/off switch.
When AC power to the turntable is turned on, automatically the preamplifier and the switched black
AC power outlets are turned on. The system will remain on until the turntable is turned off. The POWER
ON pushbutton controls the AC power for any
source other than the turntable.
Cables are supplied to interconnect the C 29 to
the power amplifier. Longer cables can be used if
needed. The length of the cable is limited by the capacitance of the cable. The total cable capacitance
must not exceed 1,000 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 10k ohms or
greater.
A second pair of MAIN OUTPUT jacks have been
supplied to feed a second power amplifier. In the
event it is desired to tape record after the tone, filter,
and volume controls the second set of OUTPUT
MAIN jacks can be connected to the tape recorder
input. The controls are then all available to control
the signal before recording. Remember, any change
in the setting of the controls will change the program to the tape recorder. Since the recording signal
available at the OUTPUT MAIN is much higher than
the output available from the OUTPUT TAPE 1 or
TAPE 2 jacks, it will be easy to over-load the tape
recorder input. In this mode of operation, it will not
be possible to monitor from the tape recorder via the
TAPE MONITOR pushbuttons while feeding the
recorder from the OUTPUT MAIN jacks. Depressing
the TAPE MONITOR pushbutton will disconnect the
program source and may cause feedback oscillation.
In the MANUAL position only the POWER ON
pushbutton will turn AC power on or off.
Some turntables have electronic circuits that
draw current all the time. To use these turntables the
AUTO/MANUAL switch must be in the MANUAL
position. With the AUTO/MANUAL switch in the
MANUAL position, AC power to the system will be
controlled by the front panel POWER pushbutton only.
The green AC power outlets are protected with a
one ampere fuse. Any increase in the value of this
fuse will affect the protection of the sensing circuit
and can cause damage.
CONNECTING PROGRAM SOURCE GROUNDS
A single GROUND post is provided to which
grounds for turntables, record changers, tape decks,
etc. are connected. To prevent hum pickup, the left
and right program cables and the ground wire from
that source should be wound or twisted together.
Make sure the ground wire does not make any connection to the shields of the left and right program
cables between the source and the input of the
preamplifier.
SPEAKER CONTROL RELAY
To control loudspeakers by use of SPEAKERS 1
and 2 pushbuttons on the front panel an accessory
Mcintosh SPEAKER CONTROL RELAY is needed.
Plug the special cable from the SPEAKER CONTROL
RELAY into the C 29 back panel SPEAKER CONTROL RELAY receptacle. In addition to loudspeaker
connections and switching, the SPEAKER CONTROL RELAY has two AC power outlets that provide
additional capacity of 2400 watts. Use these outlets
to supply AC power to amplifiers or other components whenever the total load to be switched by
the C 29 exceeds its rating of 600 watts.
FUSES
A 1.0 AMP fuse protects the preamplifier circuits.
The fuse does not protect additional equipment connected to the back panel AC outlets.
The green AC power outlets are protected with a
one ampere fuse. Any increase in the value of this
fuse will affect the protection of the sensing circuit
and can cause damage.
CONNECTING AC POWER
The preamplifier AC power cord is plugged into a
120 volt 60 Hz wall outlet.
There are two types of AC power outlets on the
back panel: four black and two green.
6
OPTIONAL SCR 2 FOR
PUSHBUTTON SWITCHING
OF MAIN AND REMOTE
SPEAKERS.
POWER
AMPLIFIER
REMOTE
SPEAKERS
MAIN SPEAKERS
POWER AMPLIFIER
SECONDARY
SYSTEM
SPEAKERS
CONNECTIONS FOR POWER AMPLIFIERS AND LOUDSPEAKERS
7
The Front Panel Controls and
How to Use Them
BALANCE and
LOUDness
The BALANCE and
LOUDness controls are
concentric. The BALANCE control (large
outer knob) adjusts for
equal volume of either
the left or right channels. The volume of the channels can be varied
relative to each.
Turning the control clockwise toward MAX
reduces the listening volume, and automatically increases the compensation by boosting bass.
INPUT SELECTOR
The six position INPUT SELECTOR controls the input program. When the INPUT SELECTOR is turned
to:
AUX 1: the output from any high level program
source requiring flat amplification is connected to
the high level input stage. Such a source could be
another tape recorder, or a television set.
left . . . turning the control to the left accents the
left channel by reducing the right channel output.
AUX 2: same as AUX 1
right . . . turning the control to the right accents
the right channel by reducing the left channel output.
LOUDness
Use the LOUDness control for full frequency
range listening at even the softest listening levels.
The LOUDness control (the small center knob of the
concentric control) provides low-frequency boost to
compensate for a hearing characteristic of the
human ear at low listening levels. The ear becomes
less sensitive to low frequencies as volume is reduced. Increased loudness compensation is therefore
desirable at lower listening levels. The loudness
control boosts the low frequencies so that the ear
hears approximately the same musical balance as it
would at higher listening levels.
FLAT: (Maximum counterclockwise rotation) Full
volume with flat frequency response. The loudness
compensation is inoperative in this position.
TUNER: the output from any AM, FM or MPX FM
tuner is connected to the high level input stage. In
the TUNER position the C 29 has flat amplification.
8
PHono 1: the output of a magnetic phono cartridge plugged into PHono 1 is connected to the low
level amplifying stages. The response of these
stages has been shaped to precisely conform to
revised RIAA standards.
loudspeaker and the right program to the right
loudspeaker.
MONO (L + R): Adds the left and right programs
together and connects to both loudspeakers.
L + R to L: Connects the left plus right program to
the left loudspeaker only.
PHono 2: Same as PHono 1
MIC: the output of any high impedance
microphone is connected to the low level input
stage. In the MIC position the C 29 has flat
amplification.
L + R to R: Connects the left plus right program to
the right loudspeaker only.
VOLUME CONTROL
The VOLUME control
is a precision step control manufactured for
Mcintosh Laboratory. It
has 32 steps with a 70
dB range, plus volume
off. Left and right channel tracking are within
1 dB. This extreme accuracy is obtained through
special electronically controlled resistance element
trimming.
MODE SELECTOR
The MODE SELECTOR facilitates the accurate adjustment of a stereo system for some differences
caused by room acoustics, loudspeaker placement
and the other components used in the system.
The MODE SELECTOR switch connects the program to the loudspeaker in seven ways:
L to L and R: Connects the left program to both
loudspeakers.
BASS
Concentric, 11 position, tone control switches adjust the bass.
The outer knob adjusts
the right channel bass
response. The inner
knob adjusts the left
channel bass response.
Left: Adjusts the bass loudness from the left loudspeaker. Clockwise rotation increases the bass
loudness while counterclockwise rotation
decreases the bass loudness. Each step of the tone
control adjusts the bass loudness about 4 dB.
R to L and R: Connects the right program to both
loudspeakers.
Right: Has the same effect on the sound from the
right loudspeaker.
STEREO REV: Connects the left program to the
right loudspeaker and the right program to the left
loudspeaker.
TREBLE
Concentric, 11 position, tone control switches adjust the treble. The outer knob adjusts the right
STEREO: Connects the left program to the left
9
c h a n n e l t r e b l e response. The inner knob
adjusts the left channel
treble response.
TAPE 1 pushbutton and to monitor the copy use
MONITOR TAPE 2 pushbutton.
TAPE COPY T2
T1 pushbutton in: connects the
output from tape recorder 2 to the input of tape
recorder 1 without affecting the program being
heard from the speakers. In this position A copy of
tape program on recorder 2 can be made on recorder
1. To monitor the original use MONITOR TAPE 2
pushbutton and to monitor the copy use MONITOR
TAPE 1 pushbutton.
Left: Adjusts the treble loudness from the
left loudspeaker. Clockwise rotation increases
the treble loudness
while counterclockwise rotation decreases the treble loudness. Each step of the tone control adjusts
the treble loudness about 4 dB.
LF-HF FILTERS
Use the LF-HF FILTERS pushbutton to reduce objectionable low and high frequency noises (below 50
Hz and above 7 kHz). With the pushbutton in, noise
is reduced; out: filters are disconnected.
Right: Has the same effect on the sound from the
right loudspeaker.
TAPE PUSHBUTTONS
SPEAKER 1 and 2
Speakers can be turned on and off when properly
connected with the accessory Mcintosh SPEAKER
CONTROL RELAY. The SPEAKER 1 and 2 pushbuttons control the operation of a SPEAKER CONTROL
RELAY when it is plugged into the C 29 rear
SPEAKER CONTROL RELAY socket.
IMPORTANT: When the C 29 is operated with either
MONITOR pushbutton at the in position, the program heard will be that from the tape recorders only.
Signal from any other source will not be heard from
the loudspeakers. To hear any other source, make
sure the MONITOR pushbuttons are OUT.
The MONITOR switches are mechanically interlocked to prevent simultaneous monitoring from
two tape recorders. If one button is at the in position, it must be pushed again to release it to the out
position before the other button can be pushed.
The SPEAKER CONTROL RELAY controls the
audio to two pairs of stereo loudspeakers. The AC
power to two AC receptacles on the SPEAKER CONTROL RELAY is controlled by the ON-OFF cycle of
the C 29. The total capacity of the SPEAKER CONTROL RELAY AC power receptacles is 2400 watts.
The C 29 is designed so it may be used with two tape
recorders. The four left pushbuttons control the
signal output of these recorders. They permit recordings to be monitored as they are being recorded, or
copying of tapes from one recorder to another while
listening to a separate program or the playback of
either recorder.
POWER ON
The POWER ON pushbutton shares AC power
control, through a current detecting switch circuit,
with the AC power switch on a turntable. On the rear
panel the TURNTABLE AUTO/MANUAL switch
selects the mode of operation.
MONITOR TAPE 1 pushbutton out: The program
source as selected by the INPUT SELECTOR is fed
to the power amplifiers and heard through the
loudspeakers; pushbutton in: Signal from a tape
recorder plugged into INPUTS TAPE 1 is fed to the
power a m p l i f i e r s and heard t h r o u g h the
loudspeakers.
When the switch is in the AUTO position and a
turntable is plugged into one of the green AC power
outlets, the AC power to the preamp and to the black
AC power outlets can be controlled by the turntable
on/off switch. When AC power to the turntable is
turned on, automatically the preamplifier and the
SWITCHED black AC power outlets are turned on.
The system will remain on until the turntable is turned off. The POWER ON pushbutton switch parallels
the automatic turntable power control feature. The
POWER ON pushbutton is used to turn on and off
power when the turntable is not used. The POWER
ON pushbutton must be out or off for the turntable
to control the AC power.
MONITOR TAPE 2 pushbutton: Functions similarly
to monitor Tape 1. It also controls the program from
a tape recorder plugged into the front panel TAPE IN
and OUT jacks. When a tape recorder is plugged into
the front jacks all the facilities normally fed to TAPE
2 on the rear panel are automatically transferred to
the front panel. The tape recorder plugged into the
TAPE 2 IN and OUT jacks on the rear panel is
automatically disconnected.
In the MANUAL position only the POWER ON
pushbutton will turn the preamplifier and black
outlet AC power on and off.
TAPE COPY T1
T2 pushbutton in: connects the
output from tape recorder 1 to the input of tape
recorder 2 without affecting the program being
heard from the speakers. In this position a copy of
the program on tape recorder 1 can be made on tape
recorder 2. To monitor the original use MONITOR
TAPE RECORDER FRONT PANEL CONNECTION
Input and output facilities are available at the
TAPE IN-OUT jacks on the front panel. These front
10
panel jacks make connections without having to get
at the rear panel. When using the front panel jacks,
the rear panel TAPE 2 facilities are disconnected
automatically. A metal shielded 1/4 inch stereo
phono plug is used for best shielding. Connections
follow the industry standards and are tip: left signal,
ring: right signal, and, sleeve: common ground.
PANLOC
Mcintosh developed PANLOC mounting brings
professional installation technique to stereo.
Depressing the PANLOC button will release the instrument. It can then be pulled toward you to the
"adjustment" position. In this position the top panel
controls can be adjusted.
HEADPHONES
The front panel HEADPHONE jack has been
designed to feed low impedance dynamic headphones. Electrostatic headphones generally require
higher power than dynamic headphones and are
connected to the output terminals on the power
amplifier.
Plug headphones into the front panel HEADPHONE jack. Adjust the front panel VOLUME control
for comfortable headphone listening. Additional top
panel HEADPHONE LEVEL controls also adjust the
loudness of the program when using headphones.
See the section below for top panel controls.
An amplifier in the C 29 provides the power that
feeds both the HEADPHONE jacks on the front
panel and the LINE OUTPUT jacks on the rear panel.
Top Panel Controls
To gain access to the top panel controls depress
the PANLOC buttons and pull the preamplifier out to
the adjust position. The controls are now easily
operated.
Best stereo performance is achieved when the
stereo system is properly balanced. For proper
balance each channel must be equal in loudness.
Use the top panel level controls to balance system
loudness.
HEADPHONE & LINE OUTPUT
A control has been provided in each channel to adjust the loudness of the program when using headphones. The controls adjust the output in each channel to the HEADPHONE jack only and do not affect
the program loudness from the loudspeakers. To adjust for comfortable headphone listening first adjust
the VOLUME control to normal room loudness.
Then, while wearing the headphones, adjust the
HEADPHONE LEVEL controls to the desired loudness level.
This procedure reserves the BALANCE control to
adjust for any unbalance in the source material, the
record, etc.
Before attempting to balance the system make
certain the front panel controls are set properly.
Set the MODE SELECTOR to MONO and the
BALANCE control at the center or 12 o'clock position. Turn the tone controls to the center or 12
o'clock position. The HF - LF pushbuttons should be
in the OUT position.
MAIN OUTPUT LEVEL
A control has been provided in each channel that
adjusts the output of the preamplifier. Use these
controls to compensate for minor differences in
room effects, loudspeaker efficiency or amplifier
gain.
With the tuner turned on, turn up the VOLUME
control on the front panel until a comfortable room
loudness is reached. Adjust the top panel MAIN
OUTPUT LEVEL controls until the loudness from
each loudspeaker is equal.
11
Specifications
PERFORMANCE LIMITS AND RATINGS
We promise you that the C 29 you buy, at the time
of your purchase, is capable of performance at or exceeding these limits or you get your money back.
Mcintosh PERFORMANCE LIMITS are the maximum
departure from performance perfection permitted
for a Mcintosh instrument.
SEMICONDUCTOR COMPLEMENT
9 Integrated Circuits
2 Transistors
11 Silicon Diodes
8 Light Emitting Diodes (LED)
1 Silicon Controlled Rectifier (SCR)
1 Dual Light Dependent Resistor Network (LDR)
FREQUENCY RESPONSE
+ 0 - 0 . 5 dB 20 Hz to 20,000 Hz
POWER REQUIREMENT
120 volts, 50/60 Hz, 45 watts
DISTORTION
.02% maximum at rated output level, 20 Hz to 20,000
Hz
SIZE: Front Panel measures 16 inches wide (40.6 cm)
by 5 7/16 inches high (13.8 cm). Chassis measures 14
3/4 inches wide (37.5 cm) by 4 13/16 inches high (12.2
cm) by 13 inches deep (30.0 cm), including PANLOC
shelf and back panel connectors. Knob clearance required is 1 1/4 inches (3.2 cm) in front of the mounting panel.
INPUT SENSITIVITY AND IMPEDANCE
Auxiliary, TUNER, TAPE 1, TAPE 2, 0.25 volts at
100,000 ohms; PHono 1 and PHono 2, 2 millivolts
(1,000 Hz) at 47,000 ohms and 65 pF; MICrophone, 2.5
millivolts at 10,000 ohms
FINISH: Front panel is anodized gold and black with
special gold/teal nomenclature i l l u m i n a t i o n .
Chassis is black.
HUM AND NOISE
Auxiliary, TUNER, TAPE 1, TAPE 2, IHFA 100 dB,
unweighted 90 dB below rated output; PHono 1,
PHono 2 IHFA 90 dB, unweighted 80 dB below 10
millivolts input, equivalent to less than 1.0 microvolt
at the input terminals; MICrophone, 1.5 microvolts at
the input terminals.
MOUNTING: Exclusive Mcintosh developed professional PANLOC
WEIGHT: 19 pounds (8.6 kg) net, 31 pounds (14.1 kg)
in shipping carton
OUTPUT LEVEL AND IMPEDANCE
MAIN: 2.5 volts with rated input, less than 100 ohms
source impedance, to operate into 10,000 ohms or
greater
TAPE: 0.25 volts with rated input, less than 200 ohms
source impedance, to operate into 10,000 ohms or
greater
HEADPHONE/LINE: 0.75 volts into 8 ohm load or 2.5
volts into 600 ohm line, 47 ohm source impedance,
level controls provided
VOLTAGE AMPLIFICATION IN DECIBELS
Auxiliary, TUNER, TAPE 1 and TAPE 2
to MAIN Output
to TAPE Output
0
to HEADPHONE/LINE Output
20 dB
dB
30 dB
PHono 1 and PHono 2 at 1 kHz
to MAIN Output
to TAPE Output
to HEADPHONE/LINE Output
62 dB
42 dB
72 dB
MICrophone
to MAIN Output
to TAPE Output
to HEADPHONE/LINE Output
60 dB
40 dB
70 dB
12
Facilities and Features
BASS CONTROLS
Separate 11 position rotary switches for each
channel, +20 dB to - 2 0 dB at 20 Hz
supplied by an amplifier in the C 29. Headphone
listening can be accomplished without the use of an
external power amplifier.
TREBLE CONTROLS
Separate 11 position rotary switches for each
channel, + 18 dB to - 18 dB at 20,000 Hz
SPEAKER SWITCHES
(Operates with accessory speaker control relay)
Turn two sets of speakers on or off when properly interconnected with the accessory SPEAKER CONTROL RELAY.
BALANCE CONTROL
Natural balance at center position, attenuation of
left or right channel by rotating control
MAIN OUTPUT LEVEL CONTROLS
Permits the balance of the entire system to be
conveniently preset.
PRECISE TRACKING VOLUME CONTROL
A precision step volume control with left to right
tracking accuracy within 1 dB through its entire
range.
SIX SOURCE INPUT SELECTOR
Auxiliary 1 and 2, TUNER, PHono 1
Microphone
HEADPHONE & LINE OUTPUT LEVEL CONTROLS
Adjusts the level and balance of the HEADPHONE/LINE output.
and 2,
MODE SELECTOR
Seven positions: Left channel only to both
speakers, Right channel only to both speakers,
Stereo Reverse, Stereo, Mono, L + R to left speaker
only, and L + R to right speaker only
TAPE MONITOR SWITCHES
Two pushbutton switches. Either of two tape
recorders can be monitored by selecting the TAPE 1
pushbutton or TAPE 2 pushbutton. They are
mechanically interlocked to accept only one
pushbutton at the IN position at one time.
TAPE COPY SWITCH
Two pushbutton switches. Either of two tape
recorders can be connected to copy from tape
recorder 1 to tape recorder 2 or vice versa. They are
mechanically interlocked to accept only one
pushbutton at the IN position at one time.
LF - HF FILTERS
Reduce unwanted high frequency noise (above 7
kHz) and low frequency rumble etc. (below 50 Hz) at
12 dB per octave rate.
FRONT PANEL TAPE JACKS
Allows connection to input and output of a tape
recorder from the front panel. Inserting plugs into
the front panel jacks disconnects the TAPE 2 circuits from the rear panel and uses the TAPE 2
facilities for the front panel jacks.
HEADPHONE JACKS
For listening with either low or high impedance
dynamic stereo headphones. Power to these jacks is
13
Technical Description
AUDIO SECTION
Each channel of the C 29 has four basic sections.
They are: phono amplifier, high level amplifier, filter
amplifier, and headphone amplifier.
frequency filter, a low frequency filter and a 20,000
Hz low pass filter. Each channel of the filter
amplifier again utilizes the same type operational
amplifier as was used in the phono stage and high
level amplifier. The resistive and capacitive
elements form a 12 dB per octave active RC filter.
The high frequency filter is a 7,000 Hz active low
pass filter. The low frequency filter is a 50 Hz active
high pass filter. The filter amplifier also forms a
20,000 Hz active low pass filter to reduce noise outside the useful sound spectrum while leaving the
preamplifier response flat to 20,000 Hz. This low
pass filter is connected at all times to reduce wide
band noise yet maintaining flat frequency response
to 20,000 Hz. The non-linear distortion of the active
filter elements in the C 29 is very low even at cutoff
frequency. This is not always the case with passive
filters that present to the driving source a very low
impedance at cutoff frequency.
PHONO AMPLIFIER
The phono amplifier uses a high technology integrated circuit operational amplifier. Its differential
input stage has been optimized for low noise and
low distortion performance. Open loop gain of this
integrated circuit is 100,000. With high open loop
gain a large amount of negative feedback can be used around the phono amplifier to further reduce
noise and distortion. The feedback network also provides precision RIAA frequency compensation. The
network uses 1% metal film resistors and 5% poly
film capacitors. To achieve low noise performance it
is essential that the feedback network be very low
impedance. As a consequence, the preamplifier
must be capable of operating as a power amplifier to
drive this impedance. The actual power output
capability of this preamplifier stage is more than 100
milliwatts, a great margin beyond that which is required.
HEADPHONE AMPLIFIER
The integrated circuit headphone amplifier is
capable of driving two pairs of dynamic headphones
with less than . 1 % harmonic distortion. The maximum output of the headphone amplifier is 2.5 volts
into 50 ohms or greater. Internal impedance of the
headphone amplifier is 47 ohms. Long shielded
cables can be used without adversely affecting the
frequency response. The headphone level controls
adjust the output level and balance of the headphone amplifier.
Input sensitivity of the phono amplifier is 2
millivolts. The gain of the amplifier is 42 dB at 1000
Hz. The phono amplifier has a very wide dynamic
range. At 1000 Hz the phono input circuit will accept
100 millivolts without overload, a voltage far greater
than the output of any current magnetic phono cartridge. Phono input overload therefore is virtually impossible. A signal level of 10 millivolts at the phono
input at 1000 Hz will produce 1.2 volts at the tape
output. The tape output has a source impedance of
200 ohms, designed to operate into a load impedance of 47,000 ohms or greater.
TURN ON DELAY
The C 29 has transient free turn on and turn off
characteristics. A light dependent resistor, time controlled, connects the output of the preamplifier to
the output jacks. The control to the resistor is derived from a long time constant that turns on approximately two seconds after the power switch. The
same circuit has a short turn off time constant
which turns off before the preamplifier's main power
supply has a chance to discharge.
HIGH LEVEL AMPLIFIER
At the input to the high level amplifier the signal
passes through the mode switch, then through the
volume control and the loudness control. The
loudness control is independent of the volume control permitting any amount of loudness compensation to be introduced regardless of the position of
the volume control. The linear high level amplifier
has a gain of 20 dB. The same type integrated circuit
operational amplifier as used in the phono amplifier
is used to minimize noise and distortion in the high
level amplifier. The feedback loop around this
amplifier uses frequency selective bass and treble
networks with two 11 position switches which allow
up to 20 dB of boost or cut at 20 Hz and up to 18 dB
of boost or cut at 20,000 Hz.
AUTO TURN ON
On the rear panel are two green AC power outlets
and an AUTO/MANUAL slide switch. 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 current that is drawn
by the turntable will be sensed and will cause a relay
to close. This relay controls the AC power to the C 29
and the black AC power outlets. When the current
drain ceases the preamplifier and the AC power
outlets will turn off. The complete system can be
controlled from the turntable off and on switch.
FILTER AMPLIFIER
The filter amplfier serves three functions: a high
14
15
FREQUENCY IN HERTZ
BASS AND TREBLE CONTROL CHARACTERISTICS
FREQUENCY IN HERTZ
PHONO EQUALIZATION (RIAA) AND MICROPHONE RESPONSE
FREQUENCY IN HERTZ
HARMONIC DISTORTION AT RATED OUTPUT
FREQUENCY IN HERTZ
LOUDNESS CONTROL CHARACTERISTICS
FREQUENCY IN HERTZ
LOW AND HIGH FREQUENCY FILTER CHARACTERISTICS
Performance Charts
The front panel POWER ON pushbutton must be
left in the off or out position for this automatic control to operate. When the rear panel slide switch is in
the manual position, only the front panel pushbutton
has control.
POWER SUPPLY
To minimize hum pickup and thus improve signal
to noise ratio the C 29 power transformer is triple
shielded. Shielding includes a copper strap, a
silicon steel strap, and a steel outer shell. The
transformer output voltage is fed to a full wave
bridge rectifier with 3,000 microfarad filter
capacitors to provide the + 24 volts for powering the
headphone amplifier and the plus voltage regulator
and - 2 4 volts for the minus regulator. The ± 1 8
volts needed for low level and operational amplifier
stages is controlled with integrated circuit voltage
regulators.
16
MCINTOSH LABORATORY INC.
2 CHAMBERS ST., BINGHAMTON, N.Y. 13903
607-723-3512
The continuous improvement of its products is the policy of
Mcintosh Laboratory Incorporated who reserve the right to
improve design without notice.
Printed in U.S.A.
039116
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