Marantz PM-4
¥ 74,800 (around 1980)
Commentary
This is a pre-main amplifier that can switch between class A and class AB using the form of external heat sink used in #14, #15 and MA-5.
A dual FET with good pair characteristics is used for the input stage of the power amplifier section, and deterioration of characteristics due to impedance change is prevented by the source follower configuration. By switching the bias current of the output stage, both A class and AB class can be enjoyed.
The power element uses a super high-ft transistor with a cutoff frequency of 90 MHz to minimize switching distortion.
By adopting an external heat sink, the operating temperature of the transistor is designed to be always maintained at around 60 ℃, less than half of the normal operating temperature of around 150 ℃.
Low-TIM design is consistent from the power amplifier section to the control section.
The bare characteristics are improved by the original 2-pole phase correction circuit, the open-loop gain is kept low at 64 dB and the NF amount is kept at 26 dB, and the transient intermodulation distortion in the high-frequency region is reduced.
The phono amplifier is a low-noise, high-gain type with a unique Low-TIM design that allows direct connection of an MC cartridge.
The RIAA curve is set to a device with a particularly low impedance particularly low impedance to improve the SN ratio of the auditory sense.
Tin-coated oxygen-free copper wires are used for the power supply circuit and output cables for speakers, etc. In addition, a power cord of 10A, twice the normal size, is used.
We are also working on the construction to shorten the wiring.
.JPG)
Model Rating
| Type | Stereo pre-main amplifier |
| Rated Output (20 Hz to 20 kHz, Both Channel Drive) | Class AB : 60W + 60W (8 Ω) Class A : 15W + 15W (8 Ω) |
| Total harmonic distortion rate (20 Hz to 20 kHz) | 0.015% (8 Ω load, at rated output) |
| Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | 0.015% (8 Ω load, at rated output) |
| Frequency characteristic | 20 Hz ~ 20 kHz + 0 -0.3 dB 5 Hz ~ 100 kHz + 0 -2dB |
| Damping factor (8 ohm load, 1 kHz) | 70 |
| Input Sensitivity / Impedance | Phono1, 2 mm : 2.5mV/47k Ω Phono1 MC : 200 μ V/100 Ω Tape, Tuner, AUX : 150mV/25k Ω |
| RIAA deviation | 20 Hz to 20 kHz ± 0.25 dB |
| Signal-to-noise ratio (IHF-A) | Phono MM:84dB Phono MC:64dB Tape, Tuner, AUX : 104 dB |
| Tone control | Low frequency : ± 10 dB (100 Hz) High frequency : ± 10 dB (10 kHz) |
| Phono maximum allowable input (1 kHz) | MM:330mV MC:25mV |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Rated power consumption (Electrical Appliance and Material Control Law) | 150W |
| External dimensions | Width 416x Height 117.5x Depth 334 mm |
| Weight | 9.5kg |