McIntosh MC225 Owner's Manual

PANEL FACILITIES
Fig. 3—End panel showing all input and output facilities.
INPUT
The input of the MC225 has a two posi-
tion lever switch to permit the amplifier to be
used in one of two ways:
(1) As a monophonic 50 watt amplifier
(2) As twin 25 watt amplifiers used with an
electronic crossover network, or two
completely separate amplifiers, or in
stereo applications.
With the input switch in the "Stereo"
position the input marked "L" and the input
marked "R" both have sensitivities of 0.5
volts when their gain controls are set fully
clockwise. The input impedance of each is
250,000 ohms. Each gain control allows
signal sources with output from 0.5 volts to
30 volts to be connected without overload-
ing the input to the amplifier. The controls
are set for 2.0 volts sensitivity by turning
them to the dot indicator.
With the input switch in the "Mono"
position the control marked "Right Mono
Gain" sets the input sensitivity at the input
marked "R."
The MONO position of the input switch
parallels the inputs to both amplifiers. When
the outputs are properly connected the
MC225 becomes a 50 watt monophonic
amplifier. The MONO input GAIN control
permits connecting signal sources up to 30
volts without overloading the amplifier's
input: The input impedance is 250,000 ohms.
OUTPUT
The two barrier terminal strips marked
OUTPUT provide stereo connections for the
normal speaker impedances of 4 ohms, 8
ohms, and 16 ohms. For monophonic opera-
tion connections for 2 ohms, 4 ohms, 8 ohms,
4
and 16 ohms are provided. The terminal
strips may also be connected for a constant
voltage output of 25 volts in either stereo
or mono.
As supplied, the secondary of the MC225
is grounded.
The barrier strip output connections are
fed from the secondary of the output trans-
former.
LINE OUTPUT (See also pages 5, 6, and 7)
The octal socket marked LINE OUTPUT
has connections for 25 volts, 70.7 volts, and
600 ohms for stereo operation and 300 ohms
for monophonic operation.
The 600 ohm winding and the 300 ohm
winding are balanced to ground. Pin 1 of the
octal socket is the center tap for these wind-
ings and is grounded.
The connections at the octal socket are
fed from taps on the cathode winding in the
primary of the output transformer.
FUSE
The MC225 uses a 2.0 ampere slo-blo
type fuse. The auxiliary AC socket is not
fused.
AC OUTLET
The auxiliary AC outlet can be used to
supply power to other equipment in the sys-
tem. The outlet will provide a maximum of
400 watts of power. The AC outlet is not
fused.
LINE VOLTAGE
The MC225 operates on line voltages
between 105 volts to 130 volts, 50 cycles to
60 cycles.

McIntosh MC225 Specifications

General

Power Output	25 watts per channel
Total Harmonic Distortion	0.5% at rated output
Input Impedance	250k ohms
Output Load Impedance	4, 8, or 16 ohms
Frequency Response	20Hz to 20kHz (+0 -0.5dB)
Signal to Noise Ratio	90dB