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High-power 4-parallel module, ODNF circuit, version 4.0
A powerful drive circuit is necessary to amplify sound signals from a control amplifier with high fidelity and to exploit the performance of various speakers. M-700u has achieved the output of up to 840 W + 840 W (1Ω) instantaneously from the rated output of 120 W + 120 W (8Ω) and 210 W + 210 W (4Ω). Speakers can be driven with its sufficient power under any load conditions. Moreover, the BLT mode allows the user to use the unit as a monaural amplifier with the rated output of 420 W(8Ω). A 4-parallel push-pull structure with 3-stage Darlington is used in this circuit to acquire such high power. The latest version, ODNF 4.0 circuit, that has achieved primary slew rate speed indicating the startup performance by feeding back only distortion components, ultra-wide bandwidth, and low level of distortion is adopted for the amplifier circuit, which is inherited from M-900u, our top-end model. Precise reproduction of a small sound signal has enhanced the elaborate sound expression and the expressive capability of tranquillity. Setting up to 6 W with which sound range can be practically and sufficiently acquired to the Class A operation range, it has made its high power consistent with sound expression of high density.
* ODNF is an abbreviation for "Only Distortion Negative Feedback".
Large-capacity power supply circuit
M-700u is equipped with high-performance EI type power transformer whose rated capacity is as much as 550 VA with a reputation for its tone quality full of dynamism including bass range perseverance to support overwhelmingly powerful power supply unit. A high level of regulation ability that is unshakable by any load fluctuation has been achieved.
Low impedance transmission
In order to transmit the powerful drive force generated by the large-scale output circuit without any loss, super-thick wires for major current systems and large-capacity speaker relays with low resistance in which 4 contacts are connected in parallel are equipped. Transmission of thoroughly low impedance has been achieved, and 350 of the damping factor has been accomplished.
Large-capacity block condenser
The combination of block capacitor with high-capacity of 80,000μF (10,000μF x 8) whose right and left channels are independent and a power transformer configures high-inertia power supply that offers both instantaneous force and a sense of stability. This unit supports the performance of M-700u from the bottom and delivers the sound dynamism amazingly.
The beeline construction is adopted, which makes the internal configuration of the power amplifier reasonable and also makes the wiring route shortest. The traditional wiring pattern of the substrate with use of copper foil of approx. 100μm in thickness allows highly pure signal transmission to be achieved.
Large type of needle-type meter
A large-scale needle-type meter is adopted to provide not only audible but also physical sensation for the lively feeling of the music. The electric bulb color of the LED illumination is the result of our persistence in dignity and visibility. This meter can be switched in 3 steps with use of the switch on the front panel as follows: Operation ON/Light ON → Operation ON/Light OFF → Operation OFF/Light OFF.
Gradation cast-iron leg
A loopless chassis structure is used for the cabinet to eliminate increased ground impedance and the effect of generated magnetic field. Gradation cast-iron insulator legs are attached to prevent resonance thanks to its characteristics of that the metallic structure becomes smaller from the center to the periphery of the leg.
Specially selected custom parts
M-700u consists of original custom parts, considering the sound quality as the first priority, such as resistances, capacitors, even all wires, which have been generated from Luxman's highly advanced know-how and sensibility accumulated in producing audio products for a long time. Those parts have contributed to realizerich tone that Luxman has pursued.