The Mclntosh
C22 Stereophonic Preamplifier is a control center for any stereophonic sound
system. To increase your enjoyment of stereo, this control center does four
jobs with precise control.
First, the
control center amplifies weak electrical impulses. As the record rotates on the
turntable, undulations in the grooves move the pickup stylus approximately one
thousandth of an inch, in any direction, from the rest position. From this
slight mechanical movement, the pickup stylus generates a weak electrical
impulse on the order of a few thousandths of a volt. To amplify and preserve
the information in such an electrical impulse, the finest amplifier performance
is required.
Second,
every sound system is used in a different acoustical environment. The tone
balance of the music is affected by variations in environment. Also, people
listening to the music have varying ideas of correct tone balance. To
compensate for these conditions, a high-quality tone control center is needed.
Third, all stereophonic and monophonic records, both domestic and foreign, are
recorded with specific frequency equalization. The control center must
accurately compensate for this equalization introduced in the recording
process.
Fourth,
programs can originate from several sources such as tuners, records, tape
machines, microphones, etc. A control center is needed to select and switch
these sources separately or in combination.
All of these
jobs are performed with Excellence by
the C22.
The C22 also
uses the new, exclusive Mclntosh PANLOC method of installation.
The PANLOC
system gives you absolute ease of installation, operation, and maintenance.
PANLOC is
the first professional installation technique to be used on stereo instruments.
In the PANLOC system a metal shelf is mounted first, then the preamplifier
slides into position on this shelf. Depressing the PANLOC buttons on the front
panel locks the preamplifier firmly into place for normal operation. To unlock
the preamplifier, depress the front panel PANLOC buttons a second time. The
preamplifier can now slide forward to the ADJUST position. The preamplifier
will lock in this position approximately 3 inches from the mounting panel.
Now you can
adjust the output level controls, low frequency trim controls, tape
equalization controls, phase switch and pilot lamp intensity switch. These
controls are mounted just behind the C22 front panel. Depressing the ADJUST
position holding latches on the sides of the chassis allows the preamplifier to
be taken out of the PANLOC shelf, or toslide back into position against the
mounting panel.
Once you
have enjoyed the outstanding performance of the C22, you will understandwhy
Mclntosh products have earned their reputation as "THE BEST." Your
Mclntosh C22 Stereophonic control preamplifier will give you years of the
finest possible performance, and will become a highly valued part of your home
music system.
TECHNICAL
DESCRIPTION
The C22
Stereophonic Preamplifier combines excellence in performance with ease of
operation. The most often used controls have large diameter knobs. A new type
of rocker switch is used for the controls with simple on-off functions. The C22
has an illuminated front panel with a light intensity switch to provide
convenient reading under low-level lighting conditions. The Mode and Input
Selector switch positions are also illuminated.
The C22
circuit consists of 3 amplifier sections in duplicate for the left and right
stereo channels together with a common power supply.
The first
amplifier section is the input preamplifier used to amplify and equalize
signals from phonograph pickups, microphones or tape heads. Skillful circuit
layout, proper grounding, and adequate shielding reduce the hum so low it is
virtually unmeasurable. Extreme care in manufacturing combined with low noise
tubes, high specific resistivity circuit boards, metal film and wire wound
resistors achieves new low in residual noise.
The second
amplifier section follows the main volume control, making it impossible to
overload the high level input circuits or any following circuits. The same
design techniques as used in the preamplifier section assure low noise and hum.
The BASS and TREBLE feedback-type tone controls operate in connection with this
amplifier section. The controls are switch-type with approximately 4 db change
per step. Exceedingly low distortion and precise control of frequency response
contours are assured using this arrangement. Front panel tape jacks are
provided for convenient use of an external tape machine. The TAPE JACK switch
connects the jacks for either playback or recording through the C22.
The third
section is the cathode follower output. The sharp cutoff (18 db per octave)
RUMBLE and HF (high frequency) filters are associated with this section. OUTPUT
LEVEL controls are located at the inputs of the cathode followers to allow
simple balance of the entire amplifier-speaker system. The OUTPUT LEVEL
controls are located on top of the C22, behind the front panel. These controls
are conveniently accessible by releasing the PANLOC buttons and sliding the C22
out to the adjust position.
The power
supply deserves special mention.
The power
transformer is constructed with "core" type grain oriented
laminations and magnetic shielding for low external humfields. Long life
rectifiers with full wave rectification, filter condenser sectionalizing and
careful grounding add to the hum-free long life characteristics of the C22.
Special attention has been given to the mechanical design. The 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 C22 may be conveniently installed in furniture cabinets,
custom-built installations, professional relay racks or an attractive finished
Mclntosh cabinet.
Specifications
Input
Sensitivity and Impedance:
Auxiliary,
Tape, Tuner 1, and Tuner 2: 0.25 volts, 250,000 Ω
Phono
1 and Phono 2: 2 millivolts, 47,000 Ω
Microphone:
2.5 millivolts, 1 megohm.
Tape Head: 2
millivolts, 1 megohm.
Tape
Compare: 0.25 volts, 250,000 Ω
Frequency
Response: ±0.5 dB from 20 cps to 20,000
cps.
Distortion:
Less than
0.2% at 10 volts output.
Less than
.02% at 3 volts output.
Total Noise:
High Level
Inputs: 85 db below rated output.
Low Level
Inputs: Less than 1.5 microvolts at input terminals.
Main
Output: 2.5 volts with rated input.
Tape
Output: .25 volts with rated input.
Left
Plus Right Output: 1 volt from generator
impedance of 25,000 Ω
Voltage
Amplification:
Auxiliary,
Tape, Tuner 1, and Tuner 2:
To Main
Output : 20 dB (10 to 1).
To Tape
Output : 0 dB (1 to 1).
Phono 1 and
Phono 2 (At 1 KC):
To Main
Output : 62 dB (1250 to 1).
To Tape
Output : 42 dB (125 to 1).
Microphone:
To Main
Output : 60 dB (1000 to 1).
To Tape
Output : 40 dB (100 to 1).
Tape Head
(At 500 cps):
To Main
Output : 62 dB (1250 to 1).
To Tape
Output : 42 dB (125 to 1).
Tape Jack
Switch: 2 position, connects panel jacks
to allow signals to be fed from or to the C22 to record or playback using an
external portable tape recorder.
Bass
Controls: Separate channel 11 position
switch type, ±20 dB at 20 cycles.
Treble
Controls: Separate channel 11 position
switch type, ± 20 dB at 20,000 cycles.
Compensator
Switch: RIAA or LP record equalization.
Tape
Switch: Normal, or Tape Monitor.
Rumble
Filter: 50 cps cutoff.
HF
Filter: 5000 cycle cutoff.
Tubes: 6 each 12AX7.
Additional
Set-Up Controls:
The
following controls are located behind the front panel on the top of the C22
chassis.
These
controls are readily accessible by depressing the PANLOC buttons to slide the
C22 forward from the mounting panel:
Output Level
Controls (L, L + R, and R): Allows the
balance of the entire system to be conveniently adjusted.
Low
Frequency Trim Controls (L and R):
Allows frequencies below 100 cps to be boosted up to 6 db to compensate
for unequal speaker response.
Tape
Equalization Controls (L and R): Adjusts
tape head input high frequency response.
Phase
Switch: 2 position, normal (0°) or
reverse (180°).
Pilot Lamp
Intensity Switch: 2 position, bright or
dim.
A.C.
Outlets:
1 x
unswitched (Red) for turntable or tape machine.
4 x
switched.
Power
Requirement: 117 volts 50/60 cps AC, 34
watts.
Dimensions:
Front
panel: 16 inches wide by 57/16 inches
high;
Chassis
(including PANLOC shelf): 15 inches wide
by 5 inches high by 13 inches deep, including connectors; clearance in front of
mounting panel including knobs, 1½ inches.
Weight: 16 pounds net, 25 pounds in shipping carton.
Finish: Anodized gold and black (front panel).