Audio Database


Pioneer M-90a
220,000yen(1988 release)

Stereo power amplifier which supplied and developed the technology which Pioneer can have.
The direct construction which shortest-izes a signal path in order to pursue three technical themes and to lose the cross interferencee of a signal,No vibrating and the absent-resonance-ized construction which suppresses an oscillation and a vibration harmful to the low load-intensity drive capacity and sound which raise the dynamic drive capacity of a speaker are put into practice.

While using a large-sized power transformer by two right-and-left independencies, the resin coating electrolytic capacitor of 10,000 micro Fx2 is adopted as each channel. Furthermore, the right and negative side of a power source is carrying out the bridge rectification of each for high speed low-noise diode by dividing into two from the coil of the power transformer. It is possible for this to supply the music signal of a large electrical power by a low distortion.
Furthermore, the power transistor was also considered as 4 parallel push pull stream composition of Pc=130W type, and the large-current supply capacity 47A is realized.

Two input terminals, compact-disk direct and a line direct, other than the power in from the usual control amplifier are carried. A level control is possible for these direct inputs.
Moreover, the copy to a tapes etc. is possible by also carrying the output-terminal for exclusive use in this compact disk/Line direct termination, and returning to control amplifier etc. from here.

The direct construction is adopted in order to attain shortest-ization of a signal path.
The high-quality sound volume and the relay itself have been arranged to the input terminal nearness near a rear panel, and it has controlled the volume through the remote shaft made from brass.
Shortest-ization of a signal path is realized without this spoiling an operationality.

In order to put into practice and suppress an internal and external oscillation, while forming a transformer into CAS Ted, a heat sink, chassis frames, and honeycomb form original with a large-sized insulator are adopted, and the oscillation is distributed in many fields.
High cast iron of the shielding effect is adopted as the transformer case of M-90a. While being filled up with a thermally conductive good pitch material between this cast iron case and the main unit of a transformer, the radiation fin was prepared and the incrementation in the internal resistance by a temperature rise is also prevented.
The thing of the 1.6mm thickness which gave the copper plating to honeycomb structure is adopted as the transformer frame supporting a transformer. Furthermore, in order to press down a frame chassis firmly, the copper plating 1.6mm thickness vibration proof honeycomb punching bottom plate is adopted.
A vibration and an oscillation of a power transistor were suppressed in the heat sink, and the aluminum extrusion honeycomb heat sink excellent also in the heat-dissipation effect is adopted as it.
Furthermore, four filling type large-sized insulators made from special cell polymer are adopted, and in order to support a transformer with weight, the insulator of five flat knots made of cast iron is also carried in the insulator.

Switching distortion has adopted the non switching circuit which is not generated theoretically, expands the area of switching distorted zero, and is attaining wide band-ization. Moreover, immediately after power-switch on and at the time of the Taishin number input, the idle current which is carrying out the drift by transition of ambient temperature is stabilized, and the occurrence of the thermal distortion resulting from this is suppressed.
Furthermore, the nonlinear distortion of an output stage is decreased by detecting and rectifying the difference of an input signal and an output signal.

The copper plating chassis which reduces a magnetic distortion sharply is adopted. Moreover, by considering it as a copper plating, it will be in the pasting status of heterogeneous metalses, and the amount of periodic damping is improving compared with the case of a single metals using.

The large-sized size power indicator (39mm x 98mm) is carried, and the Direct reading of the output transition from 2mW to 300W (8-ohm o'clock) can be carried out without a change.
Moreover, in order to make peek power easy to read, the peek hold facility for 0.6 seconds is also built in.

The non stress power cord which used the oxygen-free-high-conductivity-copper line with a polar window which suppressed the influence of external noise,Quality parts, such as the vibration proof type film system capacitor using a soft coating material, an electrolytic capacitor of a special resin coating, oxygen-free-high-conductivity-copper line product-line material, a brass cap carbon resistor, a 70-micrometer Copper-foil substrate, and a gilding input/output pin jack, are adopted.

Internal Volume

Rating of a mode
Form Stereo power amplifier
Effective output (both channel drive) 1kHz: 200W+200W (4 ohm, 0.01%)
20Hz-20kHz:200W+200W (8 ohm, 0.003%)
Dynamic power
(EIA testing signal)
800W+800W (2ohm)
550W+550W (4ohm)
300W+300W (8ohm)
THD (20Hz - 20kHz) 0.003% (200W, 8ohm)
Cross modulation distortion (50Hz:7kHz=4:1) 0.002% (at the time of an effective output)
Input sensitivity/impedance Control Amp, compact disk Direct, and Line Direct:1V/50kohm
An Output voltage/impedance compact disk/Line: 1V/1kohm
Frequency characteristic Control Amp, compact disk Direct, and Line Direct:20Hz-20kHz+0 -0.1 dB
SN ratio (A network, a short circuit) Control Amp, compact disk Direct, Line Direct: 125dB
Supply voltage AC100V, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law) 410W
Dimensions Width 457x height 163x depth of 432mm
Weight 28kg