Audio Database


398,000yen(January, 1980 release)

Stereo power amplifier which used as the base the large-sized power amplifier M-4000 put on the market in 1975, made the newest technology the injection, and raised completeness further.

The Duo beta circuitry original with LUX is carried for the improvement in a tone quality.
In this circuitry, NFB of a suitable quantity for all the bands was applied, and DC servo circuitry is combined with super-low-pass one. By this, the character of the tone quality of all the bands was decided, the revise was added to the super-low-pass one besides an audio frequency band, and the settlement as an overall has been obtained.
Moreover, in order to cancel the vicious circle of applying NFB in large quantities in order that gain may become high and may stop this so that the nakedness property of amplifier is improved, and carrying out a tone-quality failure, a nakedness property is excellent, and amplifier with little gain is made, and NFB is reduced sharply. As a result, the TIM distortion by the difference of how to require NFB in low-pass and a high region is removed.
Furthermore, DC servo circuitry has realized the low-pass play which cut the super-low-pass noise and became tight, and also enlarges a super-low-pass dumping factor, and is raising the resolution of a low-pass play. Moreover, the problem of DC drift was solved and the effect has been acquired also to the speaker protection.

While adopting four power MOS FET as an output stage and sending 300mA or more of bias currents, the notchless class A operation which does not carry out a switching operation is made combining the high-speed driver circuitry.

In order that gain suitable for a Duo beta circuitry may realize the low good amplifier of a nakedness property, a thorough review of circuitry and a material is performed and the nakedness property is pursued.
The first rank constitutes the cascode differential amplifier by FET strong against a transition of ambient temperature or a voltage dual monolithic type, and the combination of a high resisting pressure low-noise transistor, and has acquired the outstanding high region property. Moreover, the predrive stage adds a current mirror load intensity to a cascode differential-amplifier circuitry, and is aiming at the modification of a linearity. And the drive stage and an output stage constituted the pure complimentary SEPP circuit, and have taken out the Oide power by the low distortion.
In these results, the naked distortion serves as outstanding amplifier with which the naked frequency characteristic was extended on a single figure to one fifth of amplifier conventionally.

In order to carry out thorough exclusion of the interference between the right-and-left channels of an input signal, the power transformer of right-and-left full independence is begun, all the circuitries are formed into a twin monophonic recording, and it is considered as the structure which unified monophonic amplifier x2.
Moreover, the simplification of the product line is attained, the substrate was blocked and secular change have adopted little reliable glass epoxy as a material. Furthermore, careful selection adoption of the connector of hi-reliability often used for communication equipment etc. is carried out, it plates with gold also in the termination side by the side of a substrate, and the robustness of the contact is improved to the terminal area of the substrate.

Two good large-sized toroidal transformers of a regulation were adopted as the power-source part, and it has combined with the high-speed constant-voltage regulated power supply of the twin monophonic stream composition.
An output stage constant-voltage-ized even the pre-driver stage, and has made the powerful power-source part to it while it carries out the careful selection using of the tone-quality measure type mass capacitor of 15,000 micro Fx2.

Three-fold protection network is carried in M-4000A.
One is a speaker protection network, excessive DC input enters, and if DC component is detected by the output-terminal, it will work.
Moreover, when the Dainyuu power is added short-circuited +- of a speaker termination, amplifier is protected doubly in the protection network by the overcurrent detection for preventing a destructive of a transistor, and the protection network by the fuse fusing detection for power transistors.

With the metals coat type, the Detent volume of the same type as a high-class Attenuator is adopted.

The chimney type heat sink made from aluminum die-casting is adopted.

The Subsonic Filter is carried, and while giving the functionality which cuts the super-low-pass noise leading to cross modulation distortion, it is considered as the measure against DC input.

The canon connector is adopted as an output-terminal, while plating with gold at an input terminal and improving a robustness.

The grounding terminal is carried.


Rating of a mode
Form Duo beta circuit stereo power amplifier
Succession effective output (20Hz - 20kHz)
Both channel concurrent / one-side-channel operation
270W+270W (4ohms)
180W+180W (8ohms)
THD (8 ohms, 20Hz - 20kHz) 0.008% or less (180W)
Cross modulation distortion (8 ohms, 60Hz:7kHz=4:1) 0.008% or less (180W)
Frequency characteristic 100kHz [ 3Hz - ]-less than 1dB
Output bandwidth 10Hz - -100kHz three dB (0.1%)
Input sensitivity/impedance 600mV/50kohm
SN ratio (IHF-A correction) 116dB or more
Remains noise 0.2mV or less
Crosstalk (Volume maxima) - 100dB or less (1kHz)
- 80dB or less (20Hz - 20kHz)
Dumping factor 100 (at the time of an 8-ohm load intensity)
Protection network The speaker protection network by a speaker termination DC drift
The amplifier protection network by overcurrent detection
The amplifier protection network by the fuse fusing detection for power transistors
Attachment Power meter
Peek indicator (it is with the switchpoint of on/off of a peek indicator)
Meter sensitivity changeover switch (0dB-20dB)
The input level set of 22 points of 1dB space-characters Detent volume adoption
Supply voltage AC100V, 50Hz/60Hz
Power consumption
(Electrical Appliance and Material Control Law)
Dimensions Width 491x height 181x depth of 390mm
Weight 30kg