Pioneer M-90

Commentary

A completed stereo power amplifier that is compatible with digital sources by generously investing Pioneer's technologies.

The power supply section is thoroughly separated to prevent mutual interference. Large transformers are used independently on the left and right sides, and electrolytic capacitors with a total capacity of 48,000 μ F are used.
In addition, a bridge rectifier circuit with high-speed low-noise diodes is used independently on the plus and minus sides of each of the left and right sides, achieving a large current supply capacity of 47A.

The power transistor uses a Pc = 130W type 4-parallel push-pull configuration.

In addition to the normal input terminal from the control amplifier, there is also a CD direct input terminal that connects the CD player and power amplifier directly. In addition, there is also a Line direct terminal, which can be used like a CD direct terminal.
This CD/Line direct connector is also equipped with a dedicated output connector which can be returned to the control amplifier.

To keep the signal path as short as possible, the volume itself is placed near the rear panel, close to the input terminal, and can be controlled from the front via an aluminum remote shaft.

It is equipped with a non-switching circuit TypeII, which is further refined from the non-switching circuit in which switching distortion does not occur in principle. The range of 0 switching distortion is further expanded and the bandwidth is further widened.
It also stabilizes the idle current, which is constantly drifting due to changes in the outside air temperature, or when a large signal is input or just after the power switch is turned on, and suppresses thermal distortion caused by this.
In addition, the difference between the input signal and output signal is detected and corrected, and the nonlinear distortion of the output stage is suppressed to 1/30 or less.

Copper plated chassis is used to reduce magnetic strain and improve vibration attenuation due to bonding of different metals.
In addition, copper plated screws are used for screws.

A five point support system has been adopted in which an insulator is attached to the center of the body in addition to the insulator as four legs, so that the heavy transformer can be firmly supported even in the center.

It is a large size of 39mmx98mm and equipped with left and right independent indicators to display output vividly. It can directly read output changes from 2 mw to 300W without switching.
In addition, a 0.6 second peak hold function is built in to make it easier to read peak power.
The indicator can also be turned off with the switch.

In order to achieve higher quality, the parts are carefully selected.
Wiring materials include highly reliable oxygen-free copper wire, brass capped carbon resistance to suppress distortion, DC resistance, 70 μ m copper-foil base to reduce inductance, resin-case capacitor, gold-plated input pin jack, large terminal, oxygen-free copper wire AC cord with polarity display, etc.

Equipped with a 4 Ω / 8 Ω output changeover switch.

Model Rating

Type	Stereo power amplifier
Rated output (20 Hz to 20 kHz, both channel drive)	200W + 200W (4 Ω) 200W + 200W (8 Ω)
Harmonic distortion factor (20 Hz to 20 kHz)	0.003% (8 Ω at Rated Output)
Intermodulation distortion factor (50 hz : 7 khz = 4 : 1)	0.002% (20 Hz to 20 kHz, 200W, 8 Ω)
Input Sensitivity / Impedance	Control Amp In, CD Direct, Line, Direct : 1V/50k Ω
Output terminal	CD/Line Direct Out, Speaker A, B, Headset
Frequency characteristic	20 Hz ~ 20 kHz + 0 -0.1 dB
Signal-to-noise ratio	125 dB (IHF, short circuit, A network)
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	410W
External dimensions	Width 457x Height 154x Depth 430 mm
Weight	20.9kg