Marantz Model 1120
¥ 175,000 (around 1972?)
A pre-main amplifier designed to simplify the circuit and achieve a high-quality balance.
All stages of the power amplifier section are directly connected with a differential amplifier circuit on the top.
A perfect pair is created for the two stones of the differential amplifier stage, and these two stones are coupled into one to keep the same state thermally, and excellent characteristics are obtained in one stage.
A diode is used for each part to achieve perfect temperature compensation, and a special air-core coil is used to prevent degradation of the distortion factor in the high-frequency. Thus, careful phase compensation is performed.
The power transistor is a special product jointly developed by Marantz and Motorola.
The protection circuit is the same type as the Model 500. If there is a leakage current to the speaker, the relay operates and turns OFF. In addition, the timing is shifted by the relay until the amplifier is fully operational in order to prevent the click sound caused by the instantaneous rush current when the switch is turned ON as well as muting.
The power transistor is a current sensor type that controls the current of the complimentary service stage.
And in case of overheating, the thermostat of the heat sinker is set to operate.
The pre-section equalizer stage has a two stage configuration, with a differential-amplifier circuit at the top and a SEPP pure complimentary service circuit at the final stage.
In addition, the feedback loop is completely directly connected, and two stages of negative feedback are applied.
A capacitor of 1.0 μ F is inserted at the top of the differential circuit to cut off unnecessary high frequency components, and a resistor of 22M Ω is inserted to completely remove the click at the time of equalizer switching.
The tone circuit is also a two stage direct-coupled type. It has a configuration with a differential amplifier circuit on the head and the last stage is held down by a ± balance power supply. It goes up and down with selectivity in the negative feedback circuit. Normally, the two stages take the feedback of one stage and keep the input impedance large and the output impedance small.
CR type is adopted for both low and high filter stages.
The power supply for the preamplifier is a constant voltage power supply that also serves as a complete ripple filter for both the + and - sides.
Almost all parts are put together on a total of six printed circuit boards, and all switches and rotary switches are printed circuit boards. In addition, there is no shield wire that is normally routed from the input terminal to the selector switch except for one location. This is a fundamental solution to the problem of noise caused by wiring, which is a problem in high-end machines.
Instead of the usual wire wrapping method, a wire clamp is used to fix the lead wire. This structure allows each circuit board to be adjusted independently even later.
For printed circuit boards, copper foils are coated to prevent corrosion and breakage.
Switches are designed so that they can be switched at the place where they are really needed by lengthening the shaft, and the shortest connection is realized.
The back side of the input terminal board is completely shielded with copper foil to prevent induction noise from the outside. In addition, a special contact relay made in Austria is used to prevent contamination with dust and eliminate contact.
In addition, there is a space in the center of the inside that can hold 4 fist to avoid mutual interference.
Equipped with a scope out terminal that can monitor the phase characteristics of the cartridge.
Walnut cabinet and rack mount adapter were sold separately as an option.
|Type||Console stereo amplifier|
|Power Amplifier Unit|
|Continuous rated output||60W + 60W (8 Ω double-channel drive, 20 Hz to 20 kHz)|
|Total harmonic distortion factor||0.2% or Less (20 Hz to 20 kHz, Rated Output)|
|Cross modulation distortion factor||0.2% or Less (20 Hz to 20 kHz, SMPTE, at Rated Output)|
|Frequency characteristic||20 Hz ~ 20 kHz ± 0.5 dB (1W)|
|Power Band With||10 Hz to 40 kHz|
|Damping factor||30 or More (8 Ω)|
|Input sensitivity||Low Level:1.1mV
|Input impedance||Phono, Mic : 47k Ω
High Level : 25k Ω
|Gain||Phono - Pre out:60dB
Phono - Rec out:40dB
High level - Pre out:20dB
|Phono input equivalent noise||1.8 μ V or Less (Input Conversion Value)|
|Equivalent Noise||From magnetic phono input to Speaker Terminals
Better than 140 dB below 60W (8 ohm load)
|Pwer||100 VAC, 50Hz/60Hz|
|External dimensions||Width 390x Height 133x Depth 349 mm|
|Sold Separately||Walnut Cabinet WC-1 (¥ 7,900)
Rack Mount Adapter RA-1 (¥ 17,500)
Rack Mount Adapter RA-2 (¥ 6,500)