Усилители мощности стерео — Luxman MQ-88uC

The MQ-88uC is a stereo valve power amplifier from Luxman, the Japanese company founded in Osaka in 1925 that has built valve amplifiers continuously since its SQ-5A integrated of 1961. It is the revised version of the MQ-88u and is designed as the partner to the CL-38uC valve preamplifier. The main visible change from its predecessor is a dark brown chassis in place of black, chosen to match Luxman's wood-cased products, combined with a hairline-finished aluminium top panel and matt black die-cast transformer covers.

Key specs that matter

The MQ-88uC delivers 25W per channel into 4, 8 or 16 ohms from KT88 output valves in triode connection. Input sensitivity is 890mV for full output and input impedance is 32 kilohms. Frequency response is 20Hz to 20kHz (+0/-0.5dB) and 10Hz to 100kHz (+0/-3dB). THD is 0.1% at 1kHz/1W and 0.5% from 20Hz to 20kHz at 1W, and the signal-to-noise ratio is 105dB (IHF-A). The valve complement is two ECC83S, two ECC82 and four KT88, all from JJ Electronic of Slovakia. Power consumption is 170W, or 140W at idle. The amplifier measures 440 x 184 x 230mm and weighs 16.1kg.

Engineering and use context

The KT88 is a beam tetrode normally used in ultralinear or pentode mode for high power. Luxman connects it as a triode, tying the screen grid to the anode, which reduces output but lowers the valve's internal impedance and extends valve life, and a push-pull pair per channel then delivers 25W. The circuit follows the classic Mullard layout - a paralleled input stage feeds a Mullard driver and phase splitter, which in turn drives the push-pull output stage. Output transformers are a key factor in any valve amplifier, and Luxman has redesigned and reproduced its classic OY15-type transformers, keeping their original die-cast aluminium housings. Separate 4, 8 and 16-ohm terminals connect to matching taps on those transformers, so each loudspeaker load is presented to the valves at its intended impedance. The power supply uses a stable EI-core power transformer with custom filter capacitors. A variable-input mode lets a source such as a CD player connect directly, with volume adjusted at the amplifier and the input section bypassed. JJ valves were selected for reliability and long life at valve-amplifier voltages and temperatures, and every unit undergoes a final check after 48 hours of ageing following assembly.

Pairing

With its moderate power and dedicated impedance taps, the MQ-88uC suits efficient and moderately sensitive loudspeakers. The CL-38uC valve preamplifier is its intended partner, and the variable-input mode allows a simpler direct-source system.

Alternatives

Luxman's own MQ-300 is a single-ended 300B valve power amplifier for highly efficient speakers.