TheMclntoshMR-55isa superiorqualityAM-FMTunerfor,useinhomemusicsystemsandprofes-
sionalapplicationswheredistortionfreereceptionisneeded.Typicalprofessionalusesare"offtheair"re-
cording,broadcastmonitor,rebroadcasting,etc.
Athoroughperusalofthisinstructionmanualwill givegreaterenjoymentandbetterlistening.TheMR-55
isthefinesttuneravailableandcompletefamiliaritywithitsfunctionsandoperationwillresultintheout-
standingperformanceyouexpectfroma Mclntoshproduct.
SPECIFICATIONS:
AM
Sensitivity:
1.5microvolts
Selectivity:
NarrowPosition:4 K.C.Bandwidth,± 10K.C.from
centerdown53D.B.
MediumPosition:13K.C.Bandwidth,± 10K.C.from
centerdown20D.B.
BroadPosition:20K.C.Bandwidth
(MeasurementsincludeR.F.andLF.circuits.Charac-
teristicssubstantiallyunchangedoverentireR.F.tun-
ingrange.)
A.V.C.:
Exceptionallystrong;lessthan4 D.B.audiooutput
changewithinputchangesfrom10microvoltsto
100,000microvolts.
Distortion:
Lessthan1%at100%modulation
Hum:
50D.B.belowfullsignal
Bandwidth:
LF.at600K.C.—20K.C.;at1600K.C.—20K.C.
R.F.at600K.C.—21K.C.;at1600K.C.—23K.C.
AudioBandwidth:
BroadPosition± 3 D.B.—20to10K.C.
MediumPosition± 3 D.B.—20to6.5K.C.
NarrowPosition± 3 D.B.—20to2.0K.C.
SensitivitySelector:
ThreePositions
FrontEnd:
21K.C.Constantbandwidth,bandpassinput
WhistleFilter:
70D.B.rejection10K.C.
FM
Sensitivity:
3Microvoltsat100%modulation(±*75K.C.
Dev.)forlessthan3%totalnoiseanddistortion
(BasedonI.H.F.M.(proposed)standardsfor
measuringF.M.Tuners)
CaptureRatio:
1to0.8
I.F.Amplifiers:
Four
I.F.Bandwidth:
200K.C.;FlatonTop
I.F.Transformers:
Mechanicallycaptive
Limiters:
Two;zerotimeconstantgrated-beamfollowedby
a0.5microsecondpentodelimiter
LimiterandDetectorBandwidth:
2Megacycles
FrequencyResponse:
±3 D.B.;20-20,000cycles
Hum:
75D.B.belowfullsignal
A.F.C.:
Separatedetector;strong,distortionfree,com-
pletelyvariable
Drift:
±30K.C.withoutA.F.C.:negligiblewithA.F.C.
AntennaInputImpedance:
300ohmbalanced;72ohmunbalanced
Radiation:
SubstantiallybelowF.C.C.requirements
TUBE
V1—6BZ7F.M.R.F.Amplifier
V2—6BZ7F.M.ReactorandF.M.Os
V3—6AB4F.M.Mixer
V4—6BJ61stLF.Amplifier
V5—6AU62ndI.F.Amplifier
V6—6Bf63rdI.F.Amplifier
V8—6AU64thLF.Amplifier
V7—6AL5A.M.DetectorandA.V.C.Detector
V9—6AL5P.M.A.V.C.
V10—6BN61stLimiter
COMPLEMENT:
V11—6AU62ndLimiter
V12—6AL5F.M.Detector
V13—6BV8AFCDetector
V14—6BA6A.M.R.F.Amplifier
V15—6BE6A.M.Converter
V16—6AL5A.V.C.Clamper
V17—12AU7SquelchAmplifierandF.M.
Metering
V18—12AU7AudioAmplifierandCathode
Follower
SIZE:
4¾InchesHighx 14¾InchesWidex 12InchesDeep
WEIGHT:
TunerOnly:17Pounds,3 Ounces;InShippingCarton:28Pounds
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