Audio Database

The pictorial image of Model 115B

Marantz Model 115B 75,000yen( at the 1972 time(?))

Description
 
The AM/FM tuner in which traditional gyroscope touch tuning was carried.

The muting circuit consists of switching circuits of the noise amplifier of transistor 2 stone, and transistor 2 stone and FET1 stone, and the way of controlling by three kinds of inputs is used for it.
One has also removed the unnecessary signal with which the third not only removes an inter-office noise with the combination of an in-dependence-upon cage and these three factors to the direct current component of a detection output, but a second produces them just before a syntony based on the status of the noise in a wave detector based on a signal intensity.

The double tune scheme by a 2 steps of FET stream composition is used for FM front end part with the 4-unit variable condenser.

The IF amplifier consists of six elements in the light filter transistor 6 stone and phase linear type.

The symmetrical type limiter circuit of many stages with a hot carrier diode and a transistor is carried in limiters, and dynamic aperture is very narrow. Thereby, the component which does not need AM modulation component etc. is removed.

IC of a PLL scheme is adopted as the MPX section.
In the case of what carries the stereo / monophonic automatic switching circuitry, checks an input signal, and it can guarantee the quality as a stereo to, a stereo demodulator is operated automatically, and a stereo lamp turns it on.
Moreover, when an input signal is not sufficient strength, it has changed into the monophonic signal automatically.

The monophonic switchpoint is carried.

The high blend switchpoint is carried and it serves to control a negative phase noise to weak FM signal included an extreme noise and interference.

If the Attenuator switchpoint is carried and it is made IN, a signal of about 20dB will be decreased and will be added to an antenna coil.

The QUADRADIAL OUTPUT termination is carried corresponding to 4ch broadcasts.

A transformer, FM front end, AM tuner part, the supply, etc. attached the black cover, and have prevented the unnecessary radiation.

AM tuner parts are RF amplifier and Local Osillator Mixer,It consists of one IC which stored IF amplifier, a detection circuitry, and the amplifier for Signal strength indicator in one package, and one transistor which amplifies the detected audio signal.
Moreover, it has two tuning circuits which use a triple variable condenser in RF amplification part.

Rear
Internal

Rating of a mode
Form FM/AM tuner
<FM tuner part>
Tuning-frequency span 76MHz - 90MHz
Practical speed (IHF) 2.3 microvolts
Quieting slope 5 microvolts : 53dB
10 microvolts : 57dB
50 microvolts : 70dB
IF stonewalling ratio 96dB
Image stonewalling ratio 70dB
Spurious stonewalling ratio 96dB
AM supression ratio 60dB
Selectivity (IHF) 60dB
Capture ratio 1.6dB
S/N ratio 70dB
Stereo separation 42dB(1kHz)
THD mono:0.15%
stereo:0.3%
Frequency characteristic (50microsec, de-emphasis) ±1dB (50Hz - 15kHz)
<AM tuner part>
Tuning-frequency property 535kHz - 1605kHz
Practical speed 20 microvolts
Selectivity 26dB
Image stonewalling ratio 70dB(1400kHz)
S/N ratio 46dB
<Synthesis>
Power source AC100V, 50Hz/60Hz
Power consumption 25W
Dimensions Width 390x height 146x depth of 300mm
Weight Main unit: 8kg
Original-packaging weight: 13.6kg