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The Mclntosh MR-55 is a superior quality AM-FM Tuner for, use in home music systems and profes-
sional applications where distortion free reception is needed. Typical professional uses are "off the air" re-
cording, broadcast monitor, rebroadcasting, etc.
A thorough perusal of this instruction manual will give greater enjoyment and better listening. The MR-55
is the finest tuner available and complete familiarity with its functions and operation will result in the out-
standing performance you expect from a Mclntosh product.
Sensitivity:
1.5 microvolts
Selectivity:
Narrow Position: 4 K.C. Bandwidth, ± 10 K.C. from
center down 53 D.B.
Medium Position: 13 K.C. Bandwidth, ± 10 K.C. from
center down 20 D.B.
Broad Position: 20 K.C. Bandwidth
(Measurements include R.F. and LF. circuits. Charac-
teristics substantially unchanged over entire R.F. tun-
ing range.)
A.V.C.:
Exceptionally strong; less than 4 D.B. audio output
change with input changes from 10 microvolts to
100,000 microvolts.
Distortion:
Less than 1% at 100% modulation
50 D.B. below full signal
Bandwidth:
LF. at 600 K.C.—20 K.C.; at 1600 K.C.—20 K.C.
R.F. at 600 K.C.—21 K.C.; at 1600 K.C.—23 K.C.
Audio Bandwidth:
Broad Position ± 3 D.B.—20 to 10 K.C.
Medium Position ± 3 D.B.—20 to 6.5 K.C.
Narrow Position ± 3 D.B.—20 to 2.0 K.C.
Sensitivity Selector:
Three Positions
Front End:
21 K.C. Constant bandwidth, band pass input
Whistle Filter:
70 D.B. rejection 10 K.C.
V1—6BZ7 F.M. R.F. Amplifier
V2—6BZ7 F.M. Reactor and F.M. Os
V3—6AB4 F.M. Mixer
V4—6BJ6 1st LF. Amplifier
V5—6AU6 2nd I.F. Amplifier
V6—6Bf6 3rd I.F. Amplifier
V8—6AU6 4th LF. Amplifier
V7—6AL5 A.M. Detector and A.V.C. Detector
V9—6AL5 P.M. A.V.C.
V10—6BN6 1st Limiter
Tuner Only: 17 Pounds, 3 Ounces; In Shipping Carton: 28 Pounds
SPECIFICATIONS:
AM
Hum:
TUBE
4¾ Inches High x 14¾ Inches Wide x 12 Inches Deep
3 Microvolts at 100% modulation (±* 75 K.C.
Dev.) for less than 3% total noise and distortion
(Based on I.H.F.M. (proposed) standards for
measuring F.M. Tuners)
Two; zero time constant grated-beam followed by
a 0.5 microsecond pentode limiter
Limiter and Detector Bandwidth:
± 3 D.B.; 20-20,000 cycles
75 D.B. below full signal
Separate detector; strong, distortion free, com-
pletely variable
± 30 K.C. without A.F.C.: negligible with A.F.C.
Antenna Input Impedance:
300 ohm balanced; 72 ohm unbalanced
Substantially below F.C.C. requirements
COMPLEMENT:
V11— 6AU6 2nd Limiter
V12—6AL5 F.M. Detector
V13—6BV8 AFC Detector
V14—6BA6 A.M. R.F. Amplifier
V15—6BE6 A.M. Converter
V16—6AL5 A.V.C. Clamper
V17—12AU7 Squelch Amplifier and F.M.
Metering
V18—12AU7 Audio Amplifier and Cathode
Follower
SIZE:
WEIGHT:
—2—
FM
Sensitivity:
Capture Ratio:
1 to 0.8
I.F. Amplifiers:
Four
I.F. Bandwidth:
200 K.C.;Flat on Top
I.F. Transformers:
Mechanically captive
Limiters:
2 Megacycles
Frequency Response:
Hum:
A.F.C.:
Drift:
Radiation:
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