Audio Database


Exclusive M4
350,000yen(around the 1974 time)

Stereo power amplifier which was based on the true nature of the audio and challenged the threshold of the likelihood in order to make true quality articles.
It is developed by a design, using component partses, circuitry, and all the performances aiming at the highest class, and is carefully finished by handmade from an assembly of component partses to the last coordination.

Class A amplification is adopted as a circuitry.
The input circuit drove the pre-driver stage of the push pull by the differential amplifier, and has led it to the last stage of four power transistor parallel connection (8 per piece channel).
Since the push-pull circuit of a Class-A operation essentially has little distortion when the notching distortion or the transitional crossover distortion by the base store-recording effect of a transistor not coming out, and not applying NFB, also in the time of the Koide power, it is not ruined and it can tell the nuance of the source faithfully.
Moreover, since it is not concerned with the size of power but there is no variation of supply voltage, the low-pass stability and low-pass transient is excellent and the large current is sent also in the time of a non-signal, the temperature of the radiator is kept constant and has acquired the outstanding heat stability.

The peek power meter is carried in the front. This meter has come to be able to carry out the Direct reading of the large span without a sensitivity change by adopting a logarithmic comression circuitry.
Moreover, in meter, the riser has adopted the good large-sized Ferrite-type meter of a dumping early, and also at the time of a small sound volume, even if the legible location is swayed and the pulse Taishin number enters, it is pointing with sufficient flattery nature to the pointer.

The thing of reliable special edition is altogether adopted as a part.
The glass epoxy group board with high intensity and robustness is adopted as the printed circuit board, and also high-precision and reliable component partses are selected carefully and used until it results in each of resistors from a transistor.
Moreover, a power-source part has little leakage magnetic flux, and the large-sized cut-core transformer excellent in the regulation and the power source capacitor of 33,000 micro Fx2 are adopted.

In order to correspond to the big calorific value of Class-A amplifier, it has a stream composition so that the heat-dissipation effect may be considered and the interior of a chassis may form the duct for cooling, and forced-air cooling is carried out using two fans with whom the cab net lower was equipped.
Moreover, 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 which combined the conventional relay and the electronic circuitry, the holding circuit by the heat detecting element and thyristor of a posister using is added to the protection network.
A relay is driven and a speaker is separated at the same time a posister detects heat as the temperature of a radiator rising unusually, it uses the current-limiting switchpoint which a thyristor commits and is built in power amplifier and it lowers the temperature of a radiator.
At this time, the display lamp of a protection is having switched on the light with as, and unless a power switch is reset, it holds this status.
In addition to the reliable protection network where the conventional response is quick, it is coped with also about the security when a fan stops by adoption of this heat perception protection network.

Two inputs are carried and a selection of 1V and 2V can be performed according to the output of a preamplifier.

CR type Subsonic Filter of 8 dB/oct is carried at 8Hz, and switchpoint ON/OFF is possible if needed.

It is suitable in handmade high-class amplifier, and the actual measurement measured for every set is attached to it as it is.

Internal Meter

Rating of a mode
Form Class-A stereo power amplifier
Circuit system 1 step of differential PP drive
Two-step Darlington quadruple PP pure complimentary OCL scheme
(Class-A operation)
Effective output 50W+50W (8 ohm, 20Hz - 20kHz, B.C.D)
THD 0.1% or less (at the time of an effective output)
0.03% or less (at the time of 1W output)
Cross modulation distortion 0.1% or less (at the time of an effective output)
0.03% or less (at the time of 1W output)
Output bandwidth 5Hz - 70kHz (IHF, both channel drive)
Frequency characteristic 3Hz-60kHz+0 -1 dB
Input sensitivity Input1, 2:1V, 2V
Subsonic Filter 8Hz(6dB/oct)
Output-terminal Speaker (8ohm)
Dumping factor 30 (8ohm) or more
Peek meter indicating range 0.005W-100W (-40dB - +3dB)
The semiconductor used Transistor: 59 pieces
IC: Six pieces
Thyristor: One piece
Diode,others : 60
Power consumption 320W
Dimensions Width 468x height 206x depth of 385mm
Weight 27.3kg