Mitsubishi M-AV1 A/V receiver Review

Mitsubishi’s M-AV1 audio/video receiver, designed as the control center for a group of compatible components that form a complete and highly versatile a/v system, includes four channels of amplification. The front channels are rated for 125 watts each into 8 ohms from 20 to 20,000 Hz with less than 0.05 percent total harmonic distortion, the rear channels for 25 watts each into 8 ohms from 50 to 10,000 Hz with less than 0.5 percent distortion. The surround-sound decoder is compatible with Dolby-encoded video sources and has a matrix mode for adding ambience to any stereo program.

Although the M-AV1 is fairly large, it has perhaps the simplest-looking front panel we have seen on a component of this type. Only the large volume knob, a few pushbuttons, and the approximately 2x3-inch illuminated display are normally visible. Next to the display are two pairs of buttons with up/down arrow indicators, one marked SCAN and the other input. The input buttons are used to select the main program source for listening or viewing, and the scan buttons step through the tuner’s sixteen am or fm presets. The selected source or preset station appears in large characters on the display, along with such other status indications as TUNED, STEREO, MUTE, and CLIPPING. The receiver has input connections for a turntable, a CD or videodisc player (identified as CD-v), a TV monitor/receiver, two VCR’s, and digital and analog tape decks.

The remaining always-visible controls are the power switch at the lower left and a small, round pushbutton marked PUSH OPEN. Pressing this button causes the bottom of the panel to swing down, revealing more buttons, a few knobs, and a headphone jack.

The tuning buttons operate in a conventional manner except that there is no band selector as such. The up and down buttons step the tuned frequency by 200 kHz for fm and 10 kHz for am; when the end of the band is reached, the receiver automatically switches to the other band. The preset memory button is used with the tuning buttons to store selected frequencies. The speaker-selector button is used to drive either one or two pairs of speakers from the front channels. When the surround mode is selected, the second pair of speakers is automatically driven by the rear (surround) channels. The conventional balance knob is supplemented by an input balance knob to minimize leakage of the front channels into the rear ones during surround operation.

The other operations of the M-AV1 are handled in a rather unconventional manner. There are two pairs of audio function buttons with up/down arrows behind the hinged panel, one pair marked select and the other adjust. The select buttons step through fm mode (mono, stereo, and high-blend), surround mode (off, matrix, and Dolby), surround volume, bass, treble, tone defeat, loudness, subsonic filter, high-cut filter, and record monitor. For each selected function, the adjust buttons step through the available range of values or switch the function on or off.

Perhaps the most unusual control on this receiver is its display angle adjustment. The M-AV1 uses a liquid-crystal display (LCD) with green, yellow, and white letters and numerals on a dark background. An LCD normally has a narrow viewing angle; contrast and legibility are best when it is viewed head on and fall off rapidly as the angle changes. The M-AV1’s display angle knob electronically “steers” the optimum viewing angle up or down for easier viewing when the user’s eyes are not on the same level as the display.

The M-AV1 has separate record-selector buttons for audio and video programs, and either type of recording can be made independently of the program being heard through the speakers. There are direct video connections for dubbing between two VCR’s as well as S-VHS inputs and an S-VHS output. The S-type inputs and output are not switched by the receiver’s dubbing controls, requiring a direct S-cable connection between video components.

The rear apron of the receiver contains all of the audio and video input and output jacks, a 75-ohm coaxial fm antenna input, terminals for an am wire antenna or the supplied loop antenna, input/output jacks for an audio-processor loop (normally joined by jumpers), and heavy-duty binding posts for two pairs of speakers. A small slide switch bypasses the front-panel speaker selector and drives the rear speakers only from the rear-channel amplifiers in a surround mode. There are five AC outlets, three of them switched. A multipin jack is provided for direct connection to compatible Mitsubishi components for total system control through the receiver’s remote unit. A video output supplies signals to an external monitor (or a receiver with a direct video input).

The remote control is a key part of a total system based on the M-AV1. It is quite large, about 9% inches long, and is covered in a suede-like gray flocking. It can be switched by its own select button to operate the audio, TV, or VCR portions of the system. Pressing this button also lights the corresponding letters in the remote’s small display window for a few seconds.

Sliding out the bottom part of the control unit’s cover an inch or so exposes the audio and video buttons, which select various functions of those portions of the system (the audio button duplicates the SELECT button on the receiver’s subpanel). The adjust button between them varies the selected function. Sliding the cover back further reveals a number of additional buttons related to TV and VCR operation and programming. Fully opened, the remote unit is an impressive 13 inches long, but for most purposes it can be used fully closed.

The M-AV1 can supply an onscreen audio menu to a video monitor, which is a convenient way to set or review the preset tuner frequencies. The numerical keypad on the remote unit can be used for direct access to any preset station or for setting the preset memories. The on-screen menu also duplicates the status indications of the front-panel display.

The Mitsubishi M-AV1 measures 16-3/4 inches wide, 6-1/4 inches high, and 15-3/4 inches deep, and it weighs 26-1/2 pounds. Price: $1,000.

Lab Tests

With both front channels driven at 1,000 Hz into 8-ohm loads, the Mitsubishi M-AV1 clipped at 147 watts per channel. Into 4 ohms, the clipping level was 195 watts. To prevent damage to the receiver, we drove a 2-ohm load with only one channel, loading the other with 4 ohms. The 2-ohm clipping level was 218 watts. The surround (rear) channels delivered 31.5 watts to an 8-ohm load. The dynamic power output was 202 watts into 8 ohms, 338 watts into 4 ohms, and 400 watts into 2 ohms.

The input sensitivity for a 1-watt output was 14 millivolts (mv) through a high-level input and 0.22 mv through the phono input, with respective А-weighted signal-to-noise ratios of 77.5 and 72 dB. The phono input overloaded at inputs between 84 and 92 mv from 20 to 20.000 Hz. Its impedance was 48.000 ohms in parallel with 90 picofarads. The RIAA equalization error was +0, —1 dB from 20 to 20.000 Hz.

At its rated 125 watts output into 8 ohms, the receiver’s total harmonic distortion (THD) plus noise was about 0.04 percent from 20 to 20.000 Hz. At half-power and less, the distortion was 0.02 percent over that range. The 4- and 8-ohm distortion readings were similar. At 1,000 Hz, the THD plus noise varied from 0.08 percent at 1 watt to a minimum of 0.015 percent at about 60 watts. Into 4 and 2 ohms, the readings were similar except that the minimum of 0.012 percent was reached at 100 and 170 watts, respectively. The distortion in the rear surround outputs (1,000 Hz into 8 ohms) was 0.9 to 1 percent at power outputs from 10 to 30 watts, reaching 1.8 percent at 1 watt.

The frequency response with the tone controls defeated was +0, — 0.5 dB from 20 to 20,000 Hz. The bass tone control had a shelved response, with a turnover frequency shifting between 300 and 700 Hz and a maximum range of + 10, — 12 dB. The treble control had a fixed turnover frequency of 1,500 Hz and a maximum range of + 14, — 10 dB. The loudness-compensation circuit boosted both low and high frequencies moderately. With the subsonic filter, the response was down 3 dB at 50 Hz and 6 dB at 30 Hz, and with the high-cut filter the response was down 3 dB at 6,500 Hz and 6 dB at 11,000 Hz.

The response of the surround (rear) channels in the matrix mode was flat from 200 to 2,000 Hz, —7 dB at 20 Hz, and — 3 dB at 7,000 Hz. There was a 25-dB notch in the response at about 12,000 Hz, and the output returned to a — 5-dB level at 20,000 Hz.

The fm tuner section’s usable sensitivity was 15.5 dBf in mono and 21.5 dBf in stereo. The 50-dB quieting sensitivity was 19 dBf in mono and 44 dBf in stereo. With a 65-dBf input, the S/N was 76 dB in mono, 69.5 dB in stereo; distortion was 0.4 percent in mono, 1.35 percent in stereo. The distortion was not at a minimum when the tuner and our signal generator were set to the same frequency, but the offset required for a minimum reading varied from 35 to 55 kHz as the signal level was adjusted.

The fm frequency response varied over a +1.5- to — 2-dB range in the stereo mode. The channel separation was 40 to 42 dB between 1,000 and 10,000 Hz and 37.5 dB at 15,000 Hz. Below 1,000 Hz, the separation decreased linearly to 13 dB at 30 Hz. In the high-blend mode, the maximum separation was 20 dB in the 100- to 200-Hz range, falling to 10 dB at 1,000 Hz and 0 dB at 6,000 Hz and above. The high-frequency response was also slightly rolled off above 5,000 Hz, to — 6 dB at 15,000 Hz. Although the am rejection and the capture ratio were very good, the image rejection was only passable, and adjacent-channel selectivity was nonexistent. The am tuner’s frequency response, relative to its 1,000-Hz level, was +1, — 6 dB from 75 to 2,200 Hz.

Comments

Our initial attempts to use the Mitsubishi M-AV1 were frustrating, but after following our own oft-given advice, “When all else fails, read the instructions,” we began to appreciate its extraordinary versatility. We can only guess how this receiver would perform in a complete Mitsubishi a/v system, but as part of a conventional audio system it was quite satisfactory.

Although the M-AV1 has a very powerful amplifier section, its FM tuner section was less distinguished. Some of its measured characteristics—such as the channel blending, which almost eliminated stereo reception without quite being pure mono, and the relatively high stereo distortion—were reminiscent of car radios and not at all typical of today’s home tuners. Also, this is the first fm tuner we can recall testing that had zero adjacent-channel selectivity (fortunately that’s not a critical matter in most locations). The ingenious display angle control worked more or less as claimed, but the range over which the display was legible remained very limited, ± 30 degrees at most.

We used the surround portion of the receiver in its matrix mode to enhance stereo reception. The effect was comparable to other basic (nonlogic) matrix systems we have used, with some sibilant spillover into the surround channels, but it provided good front-rear separation nonetheless. Although Mitsubishi refers to Dolby Surround in its literature, its decoder is not licensed by Dolby and the receiver carries no Dolby logo on its panel (the logo does appear on the display when Dolby Surround is selected). Instead of using Dolby В noise reduction, the receiver apparently uses a Mitsubishi-developed compander circuit that is claimed to provide a wider dynamic range than the Dolby system does.

Mitsubishi’s ergonomic approach in the M-AV1 makes good sense for a product designed as a control center for a complete a/v system, for use by people who prefer to enjoy listening or watching with a minimum of involvement in operating details. After all, what could be simpler than a receiver with only one knob and almost no buttons? Especially when it works smoothly, sounds good, and does a lot more than most receivers.

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