It can be said that the volume adjustment function is the core of a control amplifier. C-900u has been equipped with the high-precision attenuator that is electronically controlled and is switched by fixed resistance, which has been used in the Luxman's 80th anniversary flagship model, C-1000f, and also with the new LECUA 1000 that has been evolved from the amplification circuit integrated type, LECUA* 1000. This type is extremely insensitive to external vibration and change in sound quality depending on sound volume positions, and also significantly excellent in durability. Increase in the number of steps from 72 to 88 allows more delicate sound volume to be adjustable without deterioration of sound quality within 0 to 87 dB. The completely balanced configured C-900u is equipped with 4 units of these new LECUA 1000s in parallel, which has achieved ideal balanced transmission. Because LECUA 1000 control is used for balance adjustment between right and left and level adjustment in the bi-amplifier output mode, there is no need for concern about the deterioration of sound quality. In addition, 3D layout is introduced in new LECUA 1000 to allow substrates to be placed in three dimensions, and the attenuator circuit is directly connected to the amplification circuit, which lead to minimize routes and improve efficiency. Only distortion components are fed back to the amplification circuit to maximize the advantage of the NFB (negative feedback), and the primary slew rate speed indicating the startup performance, ultra-wide bandwidth, and the latest version of the ODNF* circuit that hasachieved lower distortion are adopted. The ODNF circuit version 4.0 has acquired higher performance by making the first stage of the main amplifier 4 parallels, second stage Darlington connection, and the first stage of the error detection amplifier 3 parallels. Delicate sound expression can be achieved by improving the S/N performance with the amount of feedback minimized, especially improving distortion characteristics at high frequencies remarkably. We have paid special attention to the shape, weightiness, and texture of the volume knob and pursued natural high quality feeling for it because the knob has the most opportunities to be touched by the user.
The high-performance power supply circuit is configured, which consists of the CI type power transformer whose capacity is equivalent to the monaural power amplifier, B-1000f, for the voltage amplification stage under the philosophy of "Power Amplifier Driver" that drives the connected power amplifier precisely with sufficient power and a large-capacity block capacitor of 3,300μF x 4 units. The delicacy and powerfulness of sound signals are transmitted to the power amplifier with the support of the high-inertia power supply with remarkably high stability and almost no small voltage fluctuation.
C-900u has been equipped with user-friendliness, flexibility, and expandability in accordance with system environment as well as multifunction. The FL display with high visibility can usually display inputs and sound volume in a 2-stage fashion, and also zoom in the contents 4 times larger with the remote control operation. This unit is equipped with the bi-amplifier output mode in which a balanced circuit can be used as a 2-channel unbalanced output, the external pre-amplifier input that is useful for coexistence with an AV system, and the tone control electronically controlled for sound quality.
Highly rigid loopless chassis is used for the cabinet to eliminate ground loop that causes the deterioration of sound quality. Gradation cast-iron is selected for the legs to prevent resonance thanks to its characteristics of that the metallic structure becomes smaller from the center to the periphery of the leg. The legs eliminate adverse effects on the circuit parts caused by vibration from the power transformer or mounting surface. The blasted white exterior with no viewable structural screw adds a sense of high quality and dignified presence.
The remote control to be frequently used is made of aluminum with moderate weightiness. The remote control allows the user to operate a wide variety of functions of C-900u in a centralized manner with remaining seated to perform sound volume adjustment as a matter of course, the loudness function that automatically provides optimal balance adjustment in an auditory sensation according to sound volume, balanced phase presetting that can be set for each input system, the display dimming function (brightness switching), the zoom function that can be operated from some distance, and more.