STEREO POWER AMPLIFIER MC225 TABLE OF CONTENTS GENERAL DESCRIPTION 1 TECHNICAL DESCRIPTION Electrical Specifications Mechanical Specifications 1 2 3 PANEL FACILITIES Input 4 4 Output Line Output Fuse AC Outlet Line Voltage 4 4 4 4 4 INSTALLATION 5 CONNECTIONS Input—Stereo Input—Twin Amp Input—Mono 5 5 5 6 Output—Stereo or Twin Amp Output —Mono Line Output—Stereo or Twin Amp Line Output—Mono AC Power 6 6 6 7 7 OPERATING THE MC225 7 ADJUSTMENTS Input Switch-Stereo Input Switch-Mono 7 7 7 G
MC225 POWER AMPLIFIER GENERAL 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 AB 1 , AB 2 or B. Two tubes are arranged in a balanced circuit. This permits each tube to operate alternately somewhat over half the time.
Intermodulation Distortion: Less than 0.5% for any combination of frequencies from 20 cycles through 20,000 cycles if instantaneous peak power is below twice the rated power. Phase Shift: Less than ±15° 20 cycles through 20,000 cycles Frequency Range: At rated output: +0, -0.1 db 18 cycles through 30,000 cycles +0, -0.
PANEL FACILITIES Fig. 3—End panel showing all input and output facilities. INPUT The input of the MC225 has a two position 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.
INSTALLATION Adequate ventilation should always be provided in the installation of electronic instruments. The trouble free life of these instruments can be extended by adequate ventilation. It is generally found that each 10° centigrade (18°F) rise in temperature reduces the life of electrical insulation by one half. Adequate ventilation is an inexpensive and effective means of preventing insulation breakdown because of unnecessarily high operating temperatures.
INPUT-MONO The shielded cable from the program source is plugged into the jack marked INPUT-R and the input switch moved to "Mono." OUTPUT-STEREO OR TWIN AMPLIFIERS For stereo or twin channel operation it is not necessary to use the same value of load impedance on each output. Simply connect each output for the impedance desired. Warning: Do not parallel the amplifier outputs when using the amplifier as a stereo amplifier or twin channel amplifier.
For all applications using 600 ohms use Class I wiring if the installation must meet the requirements of the National Electrical Code. LINE OUTPUT-MONOPHONIC The octal socket marked LINE OUTPUT has connections for operating the MC225 monophonically at 70.7 volts, 100 ohms or 300 ohms. For operating at 25 volts connections are made at the barrier strips. To feed a 25 volt line, connect one side to the screw marked COM on the LEFT barrier strip.
on the program source equipment (i.e. tape recorder, tuner, preamplifier, etc.) to the 12 o'clock (half rotation) position. Turn the "RIGHT MONO GAIN" control on the MC225 until the loudness of the sound from the speaker is just a little louder than you normally like to listen. The volume control on the program source equipment now has the most convenient amount of loudness change in either direction from the 12 o'clock position.
LABORATORY INC. 2 CHAMBERS STREET, BINGHAMTON, N. Y. Made in U.S.A. Phone-Area Code 607-723-5491 Form No. 225-HP-761-2M AA-126-161 Printed in U.S.A.
