Предусилители — Luxman C-900u

The C-900u is a solid-state control amplifier from the Japanese maker Luxman that held the top position in its preamplifier range for about a decade, until the C-10X took over that role in 2024. It is built around balanced amplification, an electronically switched resistor attenuator and the fourth version of the ODNF feedback circuit.

Key specs that matter

Input sensitivity is 255 mV on both RCA and XLR, and input impedance is 43 kohm unbalanced and 86 kohm balanced. At the rated 1 V output, the output impedance is 90 ohm for RCA and 180 ohm for XLR, and the maximum output reaches 11 V unbalanced and 22.5 V balanced. Gain is 12 dB. Frequency response stays within 0.1 dB of flat from 20 Hz to 20 kHz and extends from 5 Hz to 120 kHz at the -3 dB points. Distortion across the audio band is 0.009% through the unbalanced output and 0.005% through the balanced one. Signal-to-noise with IHF-A weighting is 123 dB on RCA and 126 dB on XLR. Tone controls provide 8 dB of boost or cut at 100 Hz and 10 kHz. The unit consumes 42 W, falling to 2.2 W in standby, and the case measures 440 x 130 x 430 mm with a weight of 19.7 kg.

Engineering and use context

Four independent amplifier modules process the hot and cold legs of the left and right signals separately, which Luxman uses to suppress the generation of noise. Volume is set by a new version of the LECUA 1000, a precision electronically controlled attenuator with 88 steps, and four of these units operate in parallel so that the balanced path is kept intact through the volume stage. In the first amplification stage the ODNF 4.0 circuit is quadrupled in parallel, giving a very wide bandwidth. The power supply relies on a CI type transformer with the same capacity as the one in the B-1000f monaural power amplifier. The chassis follows a loopless layout that avoids ground loops, and cast iron isolator legs are used to suppress resonance. Everyday functions include remote operation with the RA-20 handset, electronic bass and treble controls on the front panel, left and right balance, a loudness function and a display zoom mode.

Pairing

With its generous voltage headroom on the balanced output, the C-900u can drive any power amplifier with line inputs, and the balanced outputs connect directly to XLR-equipped amplifiers such as Luxman's own M-series stereo and B-series monaural models.

Alternatives

The Luxman C-10X is the newer top control amplifier that replaced it, with LECUA-EX volume control in 192 steps and 15 dB of gain.