FM STEREO TUNER MR 71 TABLE OF CONTENTS CONTENTS INTRODUCTION 1 TECHNICAL DESCRIPTION 2 FRONT PANEL INFORMATION 6 BACK PANEL INFORMATION 8 INSTALLATION 8 CONNECTING Audio Outputs Stereophonic FM Multiplex Monophonic FM Remote Amplifiers Off-The-Air Recording Antenna Connections 9 9 9 9 9 9 9 OPERATING INSTRUCTIONS Stereophonic FM Multiplex Monophonic FM 11 11 11 ADJUSTMENTS Muting Threshold Dial Panel Lights Output Adjust 12 12 12 12 GUARANTEE 13 OWNER'S MANUAL MR71
THANK YOU Judging from the stereo equipment you own, you rank high among discriminating music listeners. You are probably no freshman when it comes to stereo. Never-the-less we ask you to read and carefully follow these instructions to insure a successful partnership between you and your new stereo equipment. You now have "THE BEST." Used properly you are in for thousands of hours of musical enjoyment. If you are in a hurry, read page 3 first.
TECHNICAL DESCRIPTION The MR 71 tuner has a 6DS4 high-grain Nuvistor for the first RF amplifier. The Nuvistor (triode) operates into a second triode tube to form a cascade amplifier. Careful design of the operating characteristics allows the cascade amplifier to handle a wide dynamic range of signals with excellent signal-tonoise ratio. A double-tuned RF input circuit combined with the Nuvistor-tube cascade amplifier reduces spurious signals to an extremely low value.
Your Mclntosh MR71 tuner will give you many years of pleasant and satisfactory performance. If you have any questions concerning the operation or maintenance of this tuner please contact: Customer Service Mclntosh Laboratory Inc. 2 Chambers Street Binghamton, New York Our telephone number is 723-5491. The direct dial area code is 607. GUARANTEE Mclntosh Laboratory Incorporated guarantees this equipment to perform as advertised.
MPX stereo indicator lamp. The transistor is controlled by a noise-rejecting differential detecting bridge circuit. The circuit discriminates between noise and the 19KC multiplex pilot signal. The indicator will light only on the 19KC signal present in a multiplex stereo broadcast. The MR 71 uses a new Mclntosh developed automatic mono-stereo switching circuit. (Pat. Pend.) The switching is electronic without switching clicks or transients.
SPECIFICATIONS Useable Sensitivity 2.5 microvolts at 100% modulation (±75KC deviation) for less than 3% total noise and harmonic distortion in accordance with IHF standards. Audio Frequency Response Within ½db from 20 to 20,000 cycles. Distortion Lessthan0.5%at 100% modulation ±75KC deviation Capture Ratio 1.5db at 100% modulation. Muting IF injected ultrasonic muting: at least 60db noise reduction between stations. Oscillator Drift Less than 25KC with AFC disabled; negligible with AFC in operation.
5 BLOCK DIAGRAM MR 71
FRONT PANEL INFORMATION TUNING DIAL SCALES The MR 71 has two dial scales, the 88 to 108 scale marked in megacycles and the 0-100 logging scale. The dial scale marked in megacycles indicates the positions of FM stations in the 88 to 108 megacycle band. The logging scale with linear divisions from 0-100 is located directly beneath the 88 to 108 scale. The logging scale can be used to accurately retune any station. You may find it easier to keep a record of your favorite stations by use of the logging scale.
MODE SELECTOR POWER OFF brings the tuning to minimum distortion. The AFC action repeats itself each time the tuning dial is moved to a different station. The amount of AFC action is adjustable with the AUTO FREQ. CONTROL. Full left (MIN) position of the control cuts off AFC action. Full right (MAX) position gives maximum AFC action. MONO Normally, the best tuning occurs with the AUTO FREQ. CONTROL set at or near MAX position.
BACK PANEL INFORMATION TP 2 fier which has its own master volume control. Test point TP 2 is provided for tuner circuit alignment. It is also used in conjunction with the Mclntosh Ml 2 or Ml 3. The right hand pair of AUDIO OUTPUT jacks provides audio signal controlled by the MR 71 front panel VOLUME control. Use these output jacks to connect to external power amplifier, tape recorders, or any equipment which requires continuous front panel control of tuner output volume.
CONNECTING AUDIO OUTPUTS Use the FIXED OUTPUT jacks (left-hand pair of jacks next to OUTPUT ADJ) to connect to a conventional control preamplifier which has its own volume control. Full tuner output is available at all times from the FIXED OUTPUT jacks. Use the FRONT PANEL CONTROLLED jacks to connect to a conventional control preamplifier when continuous front panel control of tuner volume is desired.
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arms as straight as possible. The dipole antenna is somewhat directional. It should be positioned for best reception of the desired stations. Experimenting with the dipole position may be necessary to reduce multipath distortion on certain stations. Since it is not convenient to continually change the position of the dipole, you may have to set it for minimum multipath on your favorite station. An outdoor FM antenna is recommended for best FM reception under all conditions.
ADJUSTMENTS MUTING THRESHOLD on the tuner back panel. Set the switch to BRIGHT for maximum panel light. Set the switch to DIM for less dial light and extended lamp life. OUTPUT ADJUST The MR 71 ultrasonic muting circuit suppresses all noise between stations. It suppresses all weaker stations not strong enough to override the background noise. The muting threshold setting determines the strength of the signal which can be heard with muting in operation.
FM STATION LOG STATION DIAL FREQ.
FM STATION LOG STATION DIAL FREQ.
FM STATION LOG STATION DIAL FREQ.
LABORATORY INC. 2 CHAMBERS STREET, BINGHAMTON, N. Y. Made in U.S.A. Phone-Area Code 607-723-5491 038-029 BE022003 Printed in U.S.A.
