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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.
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