McIntosh MR 66 Owners Manual

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MR66 STEREOPHONIC TUNER INTRODUCTION The Mclntosh MR66 is a precision engi- neered, sensitive AM-FM stereo tuner. It offers the finest possible reception of AM and FM broadcasts. Every desirable feature is included on the MR66. It is perfect for use in a stereo system where nothing less than THE BEST will do. Once you have used the MR66 and en- joyed its outstanding performance, you will understand why Mclntosh products have earned their reputation as THE BEST. The MR66 is quite flexible in operation. It receives monophonic FM, monophonic AM and stereophonic AM-FM broadcasts. It also receives FM multiplex stereophonic broad- casts with the simple addition of the Mcln- tosh MA6 multiplex adapter. The MR66 front panel control and switch facilities provide for every desirable mode of tuner operation. Your Mclntosh MR66 tuner will give you years of the finest possible AM and FM reception and will become a highly valued part of your home music system. TECHNICAL DESCRIPTION FM SECTION The MR66 FM RF tuning section uses a special cascode amplifier that amplifies the weakest signals and yet maintains low noise and freedom from spurious signals. An additional tuned RF circuit combined with a 4 gang tuning capacitor contributes greatly to the excellent selectivity and high rejection of spurious signals. A newly developed Automatic Frequency Control (AFC) circuit greatly simplifies tuning. As the tuning knob is moved, the tuner re- sponds as if there were no AFC action. Approximately 3 seconds after the dial has come to rest on a particular station, the AFC circuit gradually comes into operation. The AFC action automatically brings the electrical tuning to the correct point for minimum dis- tortion. This automatic tuning repeats its action each time the tuning dial is moved to a different station. The amount of AFC action is fully adjustable with a front panel control. The unique AFC circuit uses a variable- capacitance silicon diode in place of a con- ventional tube to improve the over-all AFC performance. The silicon diode is unaffected by temperature changes, has no warmup drift, and eliminates tube filament hum. A special temperature-compensated narrow- band detector supplies operating signals to the AFC circuit to insure positive action. The narrow-band detector also operates the FM tuning meter amplifier and the ultrasonic interstation muting circuit. Three flat-topped response IF amplifiers reject adjacent channel interference and provide adequate gain to operate both limiters on even the weakest signals. Two limiters are used to insure the best possible signal-to-noise ratio. Both the RF and IF circuits are completely shielded and exceed the FCC requirements for suppression of FM oscillator and IF frequency radiation. 1