Luxman M-900u Power Amplifier

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    The stereo power amplification M-900u, was created to bring out the best sound expression from the system. The rich gradation sound quality has been achieved from deep bass sound to clear high tone with sufficient drive force acquired by connecting the 4-parallel push-pull structural output units in parallel. Luxman's original ODNF circuit that provides both a lively feeling and ultra-low distortion has been evolved to the latest version 4.0. The transparent large analog meter produces the enjoyment of listening to music with finesse, and the exterior design with blasted white finishing encloses high power gently. The BLT connection allows the user to use the unit as an ultra-high power monaural amplifier of 600W (8Ω).
    * ODNF is an abbreviation for "Only Distortion Negative Feedback"

    The role is to amplify sound signals from the control amplifier in accordance with inputs and to vibrate the speaker units precisely. M-900u has not only acquired sufficient rated output of 150 W + 150 W (8Ω), 300 W + 300 W (4Ω) but also achieved instantaneous maximum output of up to 1,200 W + 1,200 W (1Ω). Therefore, the unit can be ready with leeway for a sound source that requires high energy and drive speakers in any circumstances without being affected by change in speaker impedance. The BLT connection allows the unit to be used as a mono amplifier with the rated output of 600 W (8Ω). For the circuit configuration with this power, 1 module of 3-stage Darlington and 4-parallel push-pull amplification circuit that is excellent in sound quality and 4x2 output in which 2 modules are combined per channel are used. The effect of the counter electromotive force from a speaker is suppressed by maintaining the damping factor to 710, and overwhelming power linearity to drive the speaker unit is achieved. The latest version, 4.0, of the ODNF circuit that performs feedback of only distortion components is introduced to the amplification circuit. Then, both the merits of NFB (negative feedback), i.e. low distortion and wide-band characteristics, and the features of a non-feedback amplifier, i.e. quick response and natural tone quality are provided. The ODNF circuit version 4.0 has the improved accuracy of detecting distortion with use of 3 parallels of the first stage of the error detection amplifier.

    The high-performance EI type super-regulation transformer is placed on the power supply to support the high power of M-900u with the aim of eliminating the loss space, minimizing the capacity between lines, reinforcing the unifying force and stabilizing the magnetic field by winding the flat-type copper coil tightly. The regulation performance that is not affected by any load fluctuation is achieved owing to the large capacity of as much as 1,250 VA.

    To provide the power of the heavy-duty power supply circuit supplied from the large-capacity block capacitor of 20,000μFx4 to the amplification circuit instantaneously without any loss, the main electric current line between the power supply unit and output stage is directly connected by hardwiring using a extremely thick OFC bus bar. To transmit the powerful drive force generated by the large-scale output circuit without loss, the large-capacity speaker relay with low resistance in which 4 contacts are connected in parallel is equipped.

    A large-scale needle-type meter is introduced to provide audible sensation but also physical sensation for the lively feeling of sound. The meter is equipped with the ON/OFF switch for operation and the ON/OFF switch for illumination. For M-900u, up to 12 W of the output is operated with pure class A.

    To prevent stray current in the chassis generated by the ground loop, M-900u uses the loopless chassis that does not have a ground loop. The gradation cast-iron is used for the legs to shut off external vibrations and relieve internally generated vibrations.

    Rated output Speaker terminal Supported Y-lug terminal dimension
    Max. output 1,200W + 1,200W (1Ω)/at stereo 2,400W (2Ω)/at monaural
    Input sensitivity 1.24V/150W (8Ω) GAIN 29.0dB
    Input impedance Unbalanced 51 kΩ Balanced 34 kΩ
    Frequency response 20Hz to 20kHz (+0, –0.1dB) 1Hz to 130kHz (+0, –3.0 dB)
    Total harmonic distortion  0.008% or less (1kHz/8Ω) 0.1% or less (20Hz to 20kHz/8Ω)
    S/N ratio 117dB
    Amplification circuit ODNF 4.0
    Output configuration Bipolar 4-parallel push-pull x 2
    Power transformer EI type 1,250VA
    Damping factor 710
    Consumption 540W 280W (under no signal) 1.0W (at standby)
    Dimensions 440(W) x 224(H) x 485(D) mm front side knob of 2mm and rear side terminal of 38 mm included in depth
    Net weight 48.0kg
    Accessories Dedicated remote cable Power cable
    Speaker terminal Supported Y-lug terminal dimension Part A Width: 14mm or less Part B Width: 7mm or more
    * Connection may not be performed depending
    on the shape of the Y-lug terminal.

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