Luxman R-406 Stereo Receiver Review

Luxman’s R-406 AM/FM stereo receiver combines a phase-locked-loop (PLL) digital-synthesis tuner with an amplifier rated to deliver 60 watts per channel into 8-ohm loads from 20 to 20,000 Hz with no more than 0.05 percent total harmonic distortion. Unlike many other stereo receivers, it also carries dynamic power ratings of 85, 120, and 132 watts into loads of 8, 4, and 2 ohms, respectively.

The R-406 measures 17-3/4 inches wide, 13-1/2 inches deep, and 4-1/2 inches high, and it weighs about 17 pounds. Its uncluttered front panel, in pale satin-finish gold, has a single large volume-control knob to the right of a display window that looks somewhat like the radio dials that almost all tuners and receivers had before digital tuning became widespread. The display window contains a digital frequency readout and red LED indicators showing the number of a selected preset channel, relative signal strength, and the selected program source.

A row of pushbuttons below the display, finished to match the panel, selects the program source: AM, FM, CD/auxiliary, phono, video sound, Tape 1, and Tape 2. Tapes can be dubbed from Tape 2 to Tape 1 while monitoring from Tape 1. The receiver can be connected to audio programs from any of three different video sources (such as a TV set, a VCR, or a videodisc player) by means of a video sound SELECTOR button. Other small front-panel buttons switch the power, connect either or both of two sets of speaker outputs to the amplifier, and activate the subsonic filter and loudness compensator. Small knobs operate the bass and treble tone controls and the balance adjustment.

Above the R-406’s display window are eight station-preset buttons; each button can be assigned to both an AM station and an FM station. The tuning controls are a pair of larger red buttons. Other buttons switch off the FM muting, which also places the tuner in its mono mode, and activate the auto seek tuning feature.

The rear apron of the R-406 contains three DIN sockets through which the receiver can be connected to a Luxman cassette deck, turntable, and CD player. All these components can then be controlled by the RC-406 wireless remote control that comes with the R-406. The remote unit switches the power and controls the volume of the receiver as well as selecting the input source, the tuning mode for AM or FM, the play and pause/stop modes of the CD player, the start/cut and cue functions of the record player, and the play, record, fast-forward, reverse, and pause functions of the cassette deck. In addition, the receiver has a jack in the rear for connecting the optional RC-101 Remote Sensor, whose long extension cable allows these control functions to be performed from another room.

The R-406 receiver has a removable, hinged AM loop antenna, inputs for 75- and 300-ohm FM antennas, and an AM wire antenna. The speaker terminals are insulated and accept the stripped ends of the speaker wires. There are three switched a.c. convenience outlets. Price: $600.

Lab Tests

During the 1-hour preconditioning period at 20 watts (one-third rated power), the top of the receiver became only moderately warm. Its output transistors are cooled by a liquid-filled heat exchanger, which operated very effectively. Our full-power testing heated up the top of the cabinet noticeably, but it never became uncomfortable to touch.

The audio amplifiers of the Luxman R-406 lived up to their impressive ratings. The 1,000-Hz output power at clipping was 78 watts per channel into 8 ohms, increasing to 105 watts into 4 ohms and 100 watts into 2 ohms. The clipping headroom (8 ohms) was 1.14 dB. With the 20-millisecond tone bursts of the dynamic power measurement, the amplifier clipped at 156 watts into 8 ohms (for a dynamic headroom of 4.15 dB), 230 watts into 4 ohms, and 132 watts into 2 ohms. The distortion was nearly constant with frequency except for a rising characteristic above 5,000 Hz. It typically measured between 0.01 and 0.02 percent at most audio frequencies and power outputs below the clipping point.

The amplifier of the R-406 has a rather high gain, requiring only 20.5 millivolts into the high-level inputs or 0.24 millivolt into the phono input for a 1-watt output. The respective A-weighted noise levels through these inputs were —78.5 and —77 dB, referred to 1 watt. Noise was the only measured characteristic in which the receiver fell appreciably short of its specifications, an optimistic 98 dB and 86 dB, respectively, for the high-level and phono inputs. Luxman’s figures may have been referred to full rated power, however, instead of the 1-watt output called for by the EIA/IHF standard, although the ratings do mention IHF measurements.

The phono preamplifier overloaded at inputs in the 140- to 166-millivolt range, depending on frequency. Its input impedance was 50,000 ohms in parallel with a very small capacitance (less than 10 picofarads). The amplifier’s slew factor was greater than 25.

The tone-control characteristics were good. The bass turnover frequency shifted between about 100 and 300 Hz as the knob was turned, and the treble response hinged at about 1,500 Hz. Oddly, when the treble control was set in the middle of its cut range, the only effect was an overall gain reduction of about 1 dB over its full frequency range. Otherwise the controls worked as expected. The loudness contours boosted both low and high frequencies moderately when the volume control was set at least 20 dB below its maximum. The subsonic filter rolled off the low-frequency response by 6 dB per octave beginning at 100 Hz. The RIAA phono equalization was accurate within ± 1 dB from 20 to 20,000 Hz.

In most respects the FM tuner section of the R-406 met its specifications, which were quite good. Its frequency synthesizer had a tuning error of 25 kHz, which degraded its usable-sensitivity measurement and to some extent the distortion measurements. The mono-usable sensitivity initially measured 17.4 dBf (4.1 microvolts, or μV), but when we retuned the generator for minimum distortion it improved to 13.5 dBf (2.6 mV). Although this measurement did not match the specified value of 10.3 dBf (1.8 μV), the difference is not significant since the more important 50-dB quieting sensitivity measured essentially as rated.

The FM noise level was an exceptionally low —82 dB in mono and — 72 dB in stereo, and the latter figure improved to —77 dB at 85 dBf (10,000 μV). The distortion was a low 0.14 to 0.15 percent in both mono and stereo, as rated.

The FM stereo channel separation was 40 to 45 dB from 130 to 15,000 Hz, falling to 23 dB at 30 Hz. The capture ratio of 1.3 dB slightly surpassed the tuner’s specified 1.4 dB, and its AM rejection of 66 dB was considerably better than the rated 56 dB. Selectivity was also good, averaging 67 dB (the rating is 60 dB). The frequency response of the AM tuner section was down 6 dB (from the 1,000-Hz level) at 33 and 2,400 Hz.

Comments

Our measurements show the Luxman R-406 to be a very competent receiver whose overall performance can be characterized as good to excellent. We were impressed by its exceptional dynamic power reserve, especially when driving low-impedance loads. Its 8-ohm dynamic headroom of 4.15 dB is certainly rare and possibly unique among receivers. The tuning error we found in its FM section is a common flaw in frequency-synthesis tuners and receivers, reflecting the frequency tolerance of the quartz-crystal oscillator that controls the synthesizer. In our view, the excellent signal-to-noise ratio of the tuner section more than compensates for this small weakness, since it provides quieter reception under “real world” conditions.

The Luxman R-406 is an attractive, easy-to-use receiver that is happily free of the design and styling excesses that have afflicted some other receivers. Moreover, we found nothing in its operation that left an unfavorable impression. It sounded first-rate with FM broadcasts, LP’s, and Compact Discs.

As our measurements show, the 60-watt rating of this receiver is very conservative. It had more than enough power to support high listening levels with speakers having fairly low efficiency, and it drove higher-efficiency speakers to window-rattling levels without signs of distress. And the amplifier section’s protection system (we assume it has one!) never shut it down during our testing, even when it was driving 2-ohm loads at clipping levels. The Luxman R-406 is one receiver that does not have to be handled with kid gloves.

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