1 FM STEREO . TUNER MR 71. TABLE OF CONTENTS. INTRODUCTION 1. TECHNICAL DESCRIPTION 2. FRONT PANEL INFORMATION 6. BACK PANEL INFORMATION 8. INSTALLATION 8. CONNECTING 9. Audio Outputs 9. CONTENTS Stereophonic FM Multiplex 9. Monophonic FM 9. Remote Amplifiers 9. Off-The-Air Recording 9. Antenna Connections 9. OPERATING INSTRUCTIONS 11. Stereophonic FM Multiplex 11. Monophonic FM 11. ADJUSTMENTS 12. Muting Threshold 12. Dial Panel Lights 12. Output Adjust 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 .
2 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. This gives you a brief outline of what each control and indicator does. Reading time for this manual is 30 minutes. This is time well spent. MR 71 FM STEREO TUNER . INTRODUCTION. The Mclntosh MR 71 is a precision engi- PANLOC is the first professional installation neered, highly sensitive FM Multiplex TUNER . technique to be used on STEREO instruments.
3 The research staff of Mclntosh Laboratory has developed five new TUNER circuit improve- In the PANLOC system a metal shelf is ments for the MR 71. mounted first. The TUNER slides into position on this shelf. Depressing the PANLOC but- 1. Automatic STEREO -mono switching that tons on the front panel locks the TUNER firmly is "clickless" and completely electronic. into place for normal operation. To unlock (Patent applied for.) the TUNER depress the PANLOC buttons a 2. Multipath indicator to eliminate multi- second time. The TUNER can now slide from path reception by showing when your anten- the front panel. The TUNER will lock into this na is rotated to the correct position for mini- position, preventing accidental release of mum multipath distortion.
4 The TUNER from the installation. Depressing 3. Double tuned input circuits before the the holding latches allows the TUNER to be first amplifier to reduce spurious re- taken out of the PANLOC shelf or to slide sponses. back into position against the mounting panel. 4. New D'Arsonval movement meters of The finest possible reception of FM mono- increased sensitivity which do not need zero phonic and FM multiplex stereophonic broad- setting adjustments. casts is assured by the Mclntosh MR 71. 5. A new computer designed filter to re- TUNER . duce noise from stations broadcasting sub- carrier auxiliary music services. No other Once you have enjoyed the outstanding TUNER uses such a filter.
5 Performance of the MR 71, you will under- stand why Mclntosh products have earned The MR 71 also uses the exclusive Mc- their reputation as "THE BEST." Your Mc- lntosh PANLOC method of installation. The lntosh MR 71 TUNER will give you years of the PANLOC system gives you absolute ease of finest possible FM reception, and will be a installation, operation, and maintenance. valued part of your home music system. 1. TECHNICAL DESCRIPTION. The MR 71 TUNER has a 6DS4 high-grain The mixer output is amplified through five Nuvistor for the first RF amplifier. The Nuvis- intermediate frequency stages with flat- tor (triode) operates into a second triode tube topped highly selective response curves.
6 To form a cascade amplifier. Careful design The IF transformers have wide band re- of the operating characteristics allows the sponse with maximum adjacent channel cascade amplifier to handle a wide dynamic rejection. Construction of the IF transformers range of signals with excellent signal-to- assures electrical stability and resistance to noise ratio. mechanical shock and vibration. More than adequate gain is provided to operate both A double-tuned RF input circuit combined limiters on the weakest signals. Two com- with the Nuvistor-tube cascade amplifier plete limiters are used for the best possible reduces spurious signals to an extremely low signal-to-noise ratio.
7 Value. Sensitivity is increased to the highest possible rating, while still retaining high A separate wide band detector handles selectivity. only audio frequencies for low distortion and wide frequency response. A newly developed Automatic Frequency Both the RF and IF circuits are completely Control (AFC) circuit greatly simplifies tuning. shielded in excess of FCC requirements for As the tuning knob is moved, the AFC circuit suppression of radiation of the FM oscillator automatically cuts off for sharpest tuning. and IF frequencies. After the station is tuned in, the AFC circuit gradually comes into operation over a 3 The MR 71 multiplex decoder uses a second interval.
8 The AFC action automatically Mclntosh developed detector. The advantage brings the tuning to minimum distortion. This of this circuit is the elimination of critical automatic tuning repeats its action each adjustments necessary with commonly used time the tuning dial is moved to a new sta- multiplex matrixing methods. The L-R (left tion. The amount of AFC action is fully ad- minus right) STEREO sidebands are detected. justable with a front panel control. Then automatically combined with the L+R. main carrier signal. The left and right chan- The AFC circuit is unique. It uses a silicon nel signals are then produced with excellent diode in place of a conventional tube.
9 The separation. silicon diode improves the overall AFC per- formance. It is unaffected by temperature A temperature stabilized 19KC amplifier changes. It has no warm-up drift and elimi- locks in a highly stable 38KC synchronous nates the chance of tube filament hum. A oscillator. This method gives exceptional temperature-compensated narrow band de- noise immunity. Balanced detectors cancel tector supplies operating signals to the AFC the 38KC signal components in the output, circuit. This insures positive AFC action. The providing low distortion and reduced sus- narrow band detector also operates the FM ceptibility to spurious signals.
10 Tape record- tuning meter amplifier and the ultrasonic ing interference is minimized by this method. muting circuit. A highly selective computer designed filter reduces noise from stations broadcasting The Mclntosh developed ultrasonic muting auxiliary music services. The filter reduces circuit automatically suppresses all intersta- the frequency band from 63-74KC approxi- tion noise, including the noises usually heard mately 50db. The filter response slope is tuning in and out of a station. Weak or distant 275db per octave. The noise is eliminated stations that can't override the background without affecting normal program material.