Marantz Model1250

Commentary

Pre-main amplifier that combines the Model3600 diameter control function and large output into one.

The equalizer amplifier section uses a 3-stage direct-coupled NF differential circuit.
The material used is carefully selected within a tolerance of ± 1% to achieve a high accuracy of ± 0.3 dB or less of the equalizer deviation. In addition, the noise problem, which cannot be avoided in the sense of hearing, is improved by repeating a hearing test and adjustment. As a result, an input equivalent noise of 0.85 μ V and a dynamic margin of 110 dB are achieved.

It uses the world's first tri-circuit.
This mechanism features two selector knobs laid out on the left side of the front panel. By using a tape recorder connected to the Tape1/Tape2 jacks on the rear panel and a recorder connected to the dubbing jacks on the front panel, Route 3 signals can be handled simultaneously.
This makes it possible to record a phono with one tape recorder, insert an FM program with another tape recorder, and listen to another source.

The tone control is also a unique tri-control and can be adjusted with independent bass, mid and treble controllers on the left and right sides.
If you want to minimize the influence on the mid-range frequency, you can use the switchover switch to compensate for changes in the low and high ranges, or you can bypass the tone control circuitry by pressing the Tone defeat switch.

The active filter circuit at the output of the preamp section carefully determines the cut-off frequency so that noise can be eliminated without affecting the sound quality of the source.

The volume used is a 4-string type volume with the attenuation specified in decibels using an attenuator method.
This volume is located immediately after the equalizer amplifier and before the tone buffer amplifier to reduce the noise level. In addition, the volume attenuation changes to a broad range depending on the rotation angle of the knob, enabling fine adjustment at lower volume levels.

The power supply unit has a large one rank capacity to withstand load fluctuations at high power.
In addition, the block capacitor was initially constructed at 28,000 μ F, but 30,000 μ F was added based on the results of the hearing test.

It is equipped with a PEP (Pure Electron Protection Device) circuit as a protection circuit and is designed to withstand a 10-minute output terminal short circuit.
It has a built-in scope output jack that allows you to visualize the audio signal with an oscilloscope.

There was a rack mount adapter sold separately.

Model Rating

Type	Pre-main amplifier
Rated Output (20 Hz to 20 kHz, Both Channel Drive)	130W + 130W (8 Ω)
Frequency characteristic	20 Hz to 20 kHz ± 0.25 dB
Total harmonic distortion rate (20 Hz to 20 kHz)	Not more than 0.1%
Intermodulation distortion factor (20 Hz to 20 kHz)	Not more than 0.1%
Power band wiz	5 Hz to 50 kHz
Damping factor	65 or More (8 Ω Load)
Gain	Phono → preamplifier output : 58 dB Phono → Recording output : 40 dB High level → preamplifier output : 18 dB
Input impedance	Phono : 47k Ω High Level : 60k Ω
Input sensitivity	Phono:1.8mV Aux:180mV
Phono input equivalent noise	0.85 μ V (Input Conversion Value)
Filter	High:9kHz Low:30Hz
Pwer	100 VAC, 50Hz/60Hz
Power consumption	450W
External Dimensions (width and height are panel dimensions)	Width 390x Height 146x Depth 316 mm
Weight	18.5kg
Attachment	Mahogany cabinet
Sold Separately	Rack Mount Adapter RA-2 (¥ 5,900)