Audio Database


Exclusive M4a
430,000yen(around the 1981 time)

Stereo power amplifier which asked the class-A-amplification circuitry for the high tone quality of the quality.

Circuitry is an input stage of the differential amplifier, drives the pre-driver stage of a push pull, and is driving the last stage of eight power transistors per single-sided channel (four-piece parallel connection).
The push-pull circuit of the Class-A operation is the circuitry which was essentially excellent also in the distortion when not applying NFB few in order to have neither notching distortion nor crossover distortion. Moreover, in order that there may be no variation of the power source by the size of power, it excels especially in low-pass stability and transient.

Capacitors, such as a Mylar, a polystyrene capacitor, and contest electrolysis, a unguided volume non-magnetic-material resistor, etc. are developing and using the thing of special edition over each of tone-quality component partses.

In order to suppress a distorted occurrence as much as possible, the oxygen-free-high-conductivity-copper line is adopted as product-line material.

The 140micro thickness Copper-foil glass epoxy group board is adopted as a substrate.
Although the conventional glass epoxy group board was sticking and using a 35micro Copper foil, in order to aim at DCR (direct current resistance) in a substrate, and a falloff of an inductance, the 140micro Copper foil used as 4 times over the past is adopted.

In order to secure the stable performance and robustness, all of an input/output terminal and the termination of each assembly are raising the conduction characteristic sharply, such as using gilding.
In order to stabilize a plating and to stick conventionally, nickel plating had been performed to the ground, but there was a distorted occurrence to which nickel originates in a hysteresis since ferromagnetic material.
It plated with the newly developed pin jack adopted as M4a on the ground of non-magnetic material which shows nickel, equivalent, or the stability beyond it, and the distorted occurrence was prevented and the stable contact performance has been obtained.

The hi-reliability and the mass (15A) power cord which performed the double insulation are adopted as a power cord.
Furthermore, the polar unification is aimed at by classifying the cable of a power cord by color by white and black, and managing the interconnection with AC plug.

A connecting cord is suppressing the distorted occurrence in a connecting cord, such as using for a pin plug the gilding plug which consists of a non-magnetic-material ground, as much as possible while using an oxygen-free-high-conductivity-copper line for a material. Moreover, the structure of the connecting cord is aiming at the reduction of the inductance by adopting a different star-quad scheme from the conventional coaxial structure which made the cable with which a signal line counters mutually gather. Furthermore, the perfect shielding according a signal line to an electrically conducting polymer material and a braid is performed.
There is little distorted occurrence by these and quality signal transmission is possible at a low loss.

In order to correspond to an exothermic of Class-A amplifier, it had the stream composition that the interior of a chassis formed the duct for cooling, and the forced-air-cooling scheme is taken using two fans with whom the cabinet lower was equipped. Furthermore, in order to stop a fan's rotation sound, a low-speed operation is carried out by a low voltage.

In addition to the outputting point direct-current potential detector where the protection network combined the conventional relay and the electronic circuitry, the protection network by the heat detecting element and thyristor of a posister using is added.


Rating of a mode
Form Stereo power amplifier
Circuit system Two steps of differentials, PP drive, two-step Darlington, quadruple PP
Pure complimentary OCL (Class-A operation)
Effective output (20Hz - 20kHz, both channel drive) 50W+50W (8ohm)
THD (20Hz - 20kHz) 0.01% or less (at the time of an effective output)
0.01% or less (at the time of 25W output)
0.01% or less (at the time of 1W output)
Cross modulation distortion 0.01% or less (at the time of an effective output)
0.01% or less (at the time of 25W output)
0.01% or less (at the time of 1W output)
Output bandwidth (IHF, both channel drive) 5Hz - 100kHz (THD 0.05%)
Frequency characteristic (at the time of 1W output) 3Hz-60kHz+0 -1 dB
Input sensitivity/impedance Input1, 2:1V, 2V/50kohm
Output-terminal Speaker: 8ohm
Dumping factor (20Hz - 20kHz, 8ohm) 30 or more
Subsonic Filter 8Hz, 6dB / oct
(IHF, A network, a short circuit)
110dB or more
The semiconductor used Transistor: 59 pieces
IC: Six pieces
Diode,others: 67 pieces
Supply voltage AC100V, 50Hz/60Hz
Power dissipation (maximum electric power consumption) 320W (Electrical Appliance and Material Control Law)
Power receptacle Power-switch un-interlocking.: One line
Dimensions Width 468x height 206x depth of 385mm
Weight 27.3kg
Adjunct A relay code with a pin plug