STEREO POWER AMPLIFIER MC275 TABLE OF CONTENTS GENERAL DESCRIPTION 1 TECHNICAL DESCRIPTION Electrical Specifications Mechanical Specifications 1 3 3 PANEL FACILITIES Input Output Line Output Fuse AC Outlet Line Voltage 4 4 4 4 4 4 5 INSTALLATION 5 CONNECTIONS Input—Stereo Input—Twin Amp Input—Mono 5 5 5 5 Speakers—Stereo or Twin Amp Speakers—Mono Line Output—Stereo or Twin Amp Line Output—Mono AC Power 5 6 6 6 7 OPERATION 7 ADJUSTMENTS Line Voltage Input Switch 7 7 7 GUARANTEE 8 FREE 3-Y
MC275 STEREO POWER AMPLIFIER GENERAL DESCRIPTION Over one million watts of amplifier output power capacity have been manufactured by Mclntosh since 1947. In this 1,000,000 watts of audio power there are less than 10 watts of distortion capacity and less than 1/100 watt of noise capacity! The dramatic difference in the quality of music reproduction when you listen through Mclntosh instruments is directly due to low distortion performance. Careful, devoted research is a way of life at Mclntosh.
In the Mclntosh Unity Coupled circuit one of the bifilar primary windings is connected through the power supply to the plate and cathode of one of the output tubes. The other bifilar primary winding is similarly connected to the other tube. All low distortion high power amplifiers use push-pull output circuits known as Class AB1, AB2 or B. Two tubes are arranged in a balanced circuit. This permits each tube to operate alternately somewhat over half the time.
ELECTRICAL Power Output: Stereo or twin amplifier—75 watts continuous per channel Monophonic—150 watts continuous Harmonic Distortion: Less than 0.5% at rated output or less, 20 cycles through 20,000 cycles. Typical performance is 0.3% or less at 20 cycles and 20,000 cycles at full power. Typical performance in the mid frequencies is 0.1% or less at full power. Intermodulation Distortion: Less than 0.
PANEL FACILITIES Fig. 3—The end panel of the MC275 showing all input and output facilities. INPUT The input of the MC275 has a three position lever switch to permit the amplifier to be used in any one of three ways: (1) As a monophonic 150 watt amplifier (2) As twin 75 watt amplifiers used with an electronic crossover network, or two completely separate amplifiers, or in stereo applications requiring 0.
system. The outlet will provide a maximum of 300 watts of power. The AC outlet is not fused. LINE VOLTAGE The MC275 operates on any line voltage be- tween 105 volts and 130 volts, 50 cycles to 60 cycles. The switch marked LINE VOLTAGE changes the tap on the primary of the power transformer. The switch can be adjusted at any time. INSTALLATION Adequate ventilation extends the troubleend of the amplifier that hold the bottom free life of electronic instruments. It is cover to the chromium chassis.
Warning: Do not parallel the amplifier outputs when using the amplifier as a stereo amplifier or twin channel amplifier. Damage to the output tubes may result if parallel operation is attempted when the output voltages are not the same phase and amplitude. Speakers are connected at the barrier strips marked OUTPUT on the left end of the panel. In compliance with the National Electrical Code, Class II wiring can be used between the speaker and the amplifier at the 4 ohm, 8 ohm, or 16 ohm connection.
COM on the RIGHT barrier strip. Connect, with another wire, the screw marked 8 on the LEFT barrier strip to the screw marked 8 on the RIGHT barrier strip. The 34 ohm and the 70.7 volt connections are the same. To connect for 34 ohms or 70.7 volts solder one of the leads to pin #1 in the octal socket. The other lead is soldered to pin #7. A wire is connected between pin #7 and pin #8. For 150 watt monophonic operation 70.
marked MONO INPUT. This jack is located below the right control knob marked GAIN. The input sensitivity in this position is 0.5 volt. The GAIN control should be adjusted to match the input voltage sensitivity of the MC275 to the output voltage of the program source. For maximum flexibility set the GAIN control as follows: turn the volume control on the program source equipment (i.e. tape recorder, tuner, preamplifier, etc.) to the 12 o'clock (half rotation) position.
LABORATORY, INC. 2 CHAMBERS STREET, BINGHAMTON, N. Y. Made In U.S.A. Phone-Area Code 607-723-5491 Printed in U.S.A.
