McIntosh C27 Owner's Manual page 16

works. Separate BASS and TREBLE controls route the
feedback signal to shape the frequency response by varying
the amount of feedback used at different frequencies.
Accurate control is accomplished by using precision capa-
citors and resistors. The output of this amplifier is fed to
the MAIN OUTPUT jacks.
CENTER CHANNEL AMPLIFIER
The CTR CHAN (center channel) amplifier is an emitter
follower arranged for very high input impedance. Unity
gain is provided at the CTR CHANnel OUTPUT jack when
both the LEFT and RIGHT channels have equal output
signals.
POWER SWITCH AND POWER OUTLETS
The pushbutton POWER switch controls AC power to
the C 27 and the four black switched outlets. Power to
the red unswitched outlet is present all the time and is
not controlled by the power switch. The red outlet is in-
tended to power turntables. The switched outlets are used
to power tuners, power amplifiers, and similar components.
POWER TRANSFORMER AND POWER SUPPLY
The C 27 power transformer uses a grain oriented silicon
steel core plus copper and magnetic steel shield bands to
eliminate any radiated magnetic hum field. The extra care
in shielding assures that the power transformer will not
radiate an external magnetic field that could introduce
hum into the amplifier circuits or an adjacent phono pickup
cartridge or tape recorder playback head.
The power supply uses zener diode reference voltage
regulation and electronic filtering. Normal power line
variations do not affect the performance of the C 27. The
turn on and off time characteristics of the power supply
are controlled to prevent turn on and off transients.
SPEAKER SWITCH AND HEADPHONE JACK
The SPEAKER switch is arranged to control two sets of
loudspeakers powered by an external power amplifier.
When connecting the speakers and power amplifier it is
important to connect the power amplifier output impe-
dance tap to the parallel impedance of the two speaker
systems used. The headphone jack is also fed from the
external power amplifier. The power amplifier is required
to make the HEADPHONE jack operate.
16