McIntosh engineers
could not be content with just another preamplifier. New concepts and new
technology have produced a preamplifier that gives you the greatest flexibility
ever. Look at the great number of ways you can enjoy the C 28 .......
Use 3 tape machines
2 with their own electronics and 1 tape playback deck with complete easy front
panel switching Built-in Headphone Amplifier listen to your favorite music - -
- privately.
Main and Remote
Loudspeaker Switching turn the main speakers on or off without affecting the
remote speakers and vice versa (operates with accessory relay).
New Low Noise Phono
Input listen to your records with a new quietness.
Individual Channel
Phono Level Controls match levels from different phono cartridges without
degrading signal to noise ratio.
Individual Channel
Output Level Controls perfect balance from your stereo always.
Individual Channel
Tone Control Switches complete, repeatable flexibility.
NEW Compensation
Control one position for loudness compensation, one position is flat and (NEW)
a third position that adds presence compensation!
NEW LOW NOISE PHONO
CIRCUITS
New records and
tapes with greatly increased dynamic range demanded new low noise circuits.
McIntosh scientists developed a new DIFFERENTIAL INPUT CIRCUIT that reduced
phono input noise levels from approximately 2.4 microvolts in an excellent
preamplifier to a new level of only 1.2 microvolts! The differential input
circuit has only been used in very sensitive professional test equipment and in
medico-electronics. The preamplifier will not overload or change distortion for
any phono input signal from 2 millivolts up to 500 millivolts. This represents
a dynamic range of approximately 3000 to 1 on a voltage basis. This fantastic
improvement necessitated extreme care in layout and manufacturing. The signal
circuits need careful shielding and wiring with coaxial cable to prevent noise
and crosstalk in the preamplifier from destroying the low noise of the input
circuit.
NEW TAPE FLEXIBILITY
With the C 28 you
can copy from one tape recorder to another while listening to a completely
different program! In addition, you can monitor the recording by simply pushing
a button and an input circuit has been provided to accept the signal from a
tape playback deck. You can use three tape machines with the C 28. There are
front panel jacks that permit the use of the third tape recorder. When plugged
into the front panel jacks the tape recorder connected to Tape Recorder 2 is
automatically disconnected and the controls provided are used with the third
tape recorder.
NEW HEADPHONE
AMPLIFIER
Use your headphones
for private listening. Ample power has been provided to power todays high
quality low impedance dynamic headphones, plus a separate power switch in the
preamplifier turns the power amplifiers on or off. It is not necessary to
operate the power amplifiers while listening to headphones.
FACILITIES AND
FEATURES
BASS CONTROLS:
11 position rotary
switch in each channel, ± 20 dB at 20 Hz.
TREBLE CONTROLS:
11 position rotary
switch in each channel, ± 18 dB at 20,000 Hz.
COMPENSATION SWITCH:
Three position
switch for Flat, Loudness, or Presence.
Loudness position
boosts low frequencies for low level
listening. Presence
position boosts mid frequencies 4 dB to increase "presence" effect.
VOLUME CONTROL:
AC power ON/OFF
switch is coupled with this control.
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:
Either of two tape
recorders can be monitored by use of either the TAPE 1 or TAPE 2 pushbutton.
TAPE COPY SWITCH:
Provides switching
to copy from tape machine 1 to tape machine 2 or vice versa without affecting
the program being heard.
LF FILTER SWITCH
(Rumble Filter):
Flat or roll-off at
12 dB per octave below 50 Hz, down
18 dB at 20 Hz.
HF FILTER SWITCH
(Scratch Filter):
Flat or roll-off at
12 dB per octave above 7,000 Hz, down 18 dB at 20,000 Hz.
SPEAKER SWITCHES
(Operates with accessory relay):
Turn the main
speakers on or off without affecting the remote speakers and vice versa.
HEADPHONE JACK:
Power to this jack
is supplied by an amplifier provided in the C 28.
LOW FREQUENCY TRIM
CONTROLS:
Use to compensate
for unequal speaker response or the unequal influence of room acoustics.
PHONO 1 AND PHONO 2
LEVEL CONTROLS:
Provides for optimum
signal to noise ratio and proper balance of the channels of the phono
cartridge.
OUTPUT LEVEL
CONTROLS:
Permits presetting
the balance of the entire system.
HEADPHONE LEVEL
CONTROLS:
Adjusts the output
of the headphone/line amplifier output.
TRANSISTOR
COMPLEMENT:
26 silicon-planar
transistors, 4 silicon diodes, 2 silicon bridge rectifiers.
Specifications
FREQUENCY
RESPONSE: +0-0.5 dB 20 Hz to 20,000 Hz
DISTORTION: Will not exceed 0.1% at rated output level,
20 Hz to 20,000 Hz.
INPUT SENSITIVITY
AND IMPEDANCE:
Aux, Tuner, Tape 1,
Tape 2 : 0.25 volts / 250,000 ohms.
Phono 1 and Phono 2
: 2 millivolts / 47,000 ohms (1,000 Hz).
Microphone : 2.5
millivolts / 500,000 ohms.
Tape Head : 2
millivolts / 500,000 ohms (500 Hz).
HUM AND NOISE:
Aux, Tuner, Tape 1,
Tape 2 : 90 dB below rated output.
Phono 1, Phono 2 and
Tape Head : 78 dB below 10 millivolts input, equivalent to less than 1.2
microvolts at the input terminals. Microphone : equivalent to less than 1.5
microvolts at the input terminals.
OUTPUT LEVEL AND
IMPEDANCE:
Main Output : 2.5
volts with rated input, 100 ohms source impedance, to operate into 47,000 ohms
or more.
Tape Output : 0.25
volts, 150 ohms source impedance, from low level inputs, to operate into 47,000
ohms or more.
Headphone/Line
Output : 0.75 volts into 8 ohm load or 2.5 volts into 600 ohm line, 0.2 ohm
source impedance,
Center Channel
Output : 1.25 volts with rated input to both channels, to operate into 47,000
ohms or greater.
AMPLIFICATION IN
DECIBELS:
Aux, Tuner, Tape 1
and 2:
to Main Output : 20
dB;
to Tape Output : 0
dB;
to Headphone/Line
Output : 17.5 dB.
Phono 1 and Phono 2
at 1,000 Hz:
to Main Output : 62
dB;
to Tape Output : 42
dB;
to Headphone/Line
Output : 59.5 dB.
Microphone:
to Main Output :
60dB;
to Tape Output : 40
dB;
to Headphone/Line
Output : 57.5 dB.
Tape Head at 500 Hz:
to Main Output : 64
dB;
to Tape Output : 44
dB:
to Headphone/Line
Output : 61.5 dB.
POWER
REQUIREMENT: 120 volts, 50/60 Hz, 45
watts.
DIMENSIONS: Front panel measures 16 inches wide (40.64
cm) by 5-7/16 inches high (13.81 cm). Chassis measures 15 inches wide (38.1 cm]
by 5 inches high (12.7 cm) by 13 inches deep (33.02 cm) including PANLOC
mounting brackets and back panel connectors. Knob clearance required is 1-1/2
inches (3.81 cm) in front of the mounting panel.
FINISH: Front panel is anodized gold and black with
special gold/ teal nomenclature illumination. Chassis is black.
MOUNTING: Exclusive Mclntosh developed professional
PANLOC.
WEIGHT: 25 pounds (11.34 kg) net, 37 pounds (16.78
kg) in shipping carton.
