Marantz Model 3250 ¥ 85,000 (released in 1977)
Commentary
As a control console, it is a control amplifier that pursues rich functions.
The equalizer amplifier uses a specially designed low-noise differential input amplifier,
buffer amplifier and A-class amplifier with constant current load. It uses a 5-transistor first stage
differential and 3-stage direct-coupled differential circuit, resulting in a 300mV follower load,
40 dB closed-loop gain, and minimal RIAA deviation.
Built-in MC head amplifier with low distortion design.
This circuit is not a conventional multi-use FET, but a new super low-noise high-gain type FET
developed for audio applications. It realizes excellent S/N and low distortion factor. This FET
has approximately five times the capacity of the conventional FET. Various characteristics such
as distortion factor, S/N and frequency characteristics are greatly improved at the element stage.
In addition, it realizes a high gain of 26 dB and sufficient sensitivity of 90 μ V. It can be used
for MC cartridges by simply switching the selector.
In addition to the conventional Bass and Treble, a Mid-position tritone control is used for the
tone control section.
The tone amplifier consists of a differential amplifier and is a low-distortion NF type. In addition,
it is a linear slide type similar to a graphic equalizer for easy fine adjustment.
This circuit also has a turn-over frequency switching function and a tone defeat function that
enables one touch jump in the circuit.
It is equipped with a loudness contour.
The loudness contour adopted in the Model3250 has a structure in which the optimum
Fletcher Munson curve is set continuously variable at each stage of low volume, and it is
independent of the master volume.
When this circuit is OFF, flat frequency characteristics can be obtained.
The high filter uses a Bessel type filter with excellent roll-off characteristics, and achieves
a steep roll-off curve of 18 dB per octave at 9 kHz, thereby successfully reducing phase distortion.
It is equipped with an independent tape copy circuit capable of mutual dubbing and monitoring.
Equipped with a tape selector that can switch between up to 2 pairs.
Gold-plated terminals are used for input / output terminals.
The wood case was sold separately as an option.
You can choose the finish of the exterior of this wood case, and there are 2 kinds of variations,
walnut and mahogany.
Model Rating
Type Control amplifier
Rated Output / Impedance Pre out : 1.5V/220 Ω
Tape out : 180mV/330 Ω
Input Sensitivity / Impedance Phono1 : 1.8mV/47k Ω
Phono2 MC : 90 μ V/40 Ω
Aux, Tape : 180 mv
Total harmonic distortion factor 0.01%
Cross modulation distortion factor 0.01%
Frequency characteristic 20 Hz ~ 20 kHz + 0 -0.1 dB
RIAA deviation 20 Hz to 20 kHz ± 0.2 dB
Input equivalent noise 0.24 μ V (Phono1, IFF-A)
Tone control Bass : + / - 10 dB
Treble : + / - 10 dB
Mid : ± 6 dB
High filter 9 kHz, 18dB/oct.
Low filter 15 Hz, 18dB/oct.
Power consumption 11W
External dimensions Width 416x Height 146x Depth 243 mm
Weight 6.5kg
Sold Separately Wood Case WC-121 (Walnut Finish, ¥ 6,000)
Wood Case WC-121N (Mahogany Finish, ¥ 11,000)
Marantz Model 170DC ¥ 125,000 (released in 1977)
Commentary
With the theme of eliminating TIM (transient intermodulation distortion), this is a stereo power
amplifier refined from Marantz's tradition with the latest technology.
It has a fully independent symmetrical layout like the model250. It has a pure complimentary
service OCL parallel push-pull 3-stage Darlington circuit with a DC-configuration. It is also
designed to be resistant to load resistance and superior in power linearity by using a specially
designed low-noise element.
In addition, a differential amplification cascode bootstrap circuit using audio specification
low-noise dual FET is adopted in the first stage to minimize the problem of temperature drift
and time drift in the DC amplifier and realize stable DC.Portable audio amplifiers
A large transformer and a 18,800 μ Fx2 large capacitor are used for the power supply.
The ESP circuit adopted in the P510M is mounted in the protection circuit.
This circuit instantaneously detects excessive output current or voltage or DC generation at
the output terminal, and limits the signal to the driver transistor to a safe value. It also detects
the frequency and time. It also detects the value of the total energy, so it protects the program
without intermediate steps.
It is also equipped with a relay a relay with a delay circuit (4 seconds) to prevent shock noise
caused by power ON, and automatically separates and protects the speakers.
Equipped with a large power meter.
Unlike other VU meters, this meter can monitor the peak output level of the left and right
channels, and can read directly in the range of -40dB to + 3 dB by using logarithmic compression.
Equipped with a peak indicator for easy level adjustment.
The DC/AC change-over switch is installed on the Model170DC to solve the problem of
DC leakage of the preamp to be combined with the DC power amplifier.
The wood case was sold separately as an option.
You can choose the finish of the exterior of this wood case, and there are 2 kinds of variations,
walnut and mahogany.
Model Rating
Type Stereo power amplifier
Rated Output (20 Hz to 20 kHz, Both Channel Drive) 110W + 110W (4 Ω)
90W + 90W (8 Ω)
Total harmonic distortion factor 0.03%
Cross modulation distortion factor 0.03%
Frequency characteristic 20 Hz ~ 20 kHz + 0 -0.2 dB
Input Sensitivity / Impedance 1.5V/30k Ω
Residual noise (IHF-A) 0.046mV
Damping factor 60
Power consumption 225W (Electrical Appliance and Material Control Law)
490W maximum
External dimensions Width 416x Height 146x Depth 301 mm
Weight 14.1kg
Sold Separately Wood Case WC-110 (Walnut Finish, ¥ 7,000)
Wood Case WC-110N (Mahogany Finish, ¥ 12,000)
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