Nikko NR-750 Stereo Receiver Review

Nikko’S NR-750, a moderately priced stereo receiver, offers a full complement of operating features in a compact and attractive package. Its digital-synthesis AM/ FM tuner can operate in a scanning mode (stopping on each receivable signal) or it can be tuned manually in steps of 200 kHz for FM and 10 kHz for AM. The audio preamplifier has inputs for one high-level source (identified as CD/video) and a moving-magnet phono cartridge as well as input and output jacks for two tape decks. Front-panel switches can connect the decks for dubbing from tape 1 to tape 2. The audio amplifiers are rated to deliver 48 watts per channel into 8-ohm loads from 20 to 20,000 Hz with no more than 0.04 percent distortion.

Like many other digital-synthesis receivers, the Nikko NR-750 has a front-panel display window that shows its complete operating status at all times. Unlike some we have seen, however, its multicolored display is more informative than decorative. The tuner displays include the tuned frequency and band, the number of a selected preset station (each of the seven preset buttons can store the frequencies of one FM and one AM station), a red stereo indicator, and a signal-strength indicator in the form of a rectangular matrix of luminous dots whose color changes from red to orange to green as the signal strength increases. Other indicators show the selected program source, the status of the tape inputs and dubbing connections, and which of the two sets of speaker outputs is connected (both pairs can be connected simultaneously since they have separate selector buttons). Finally, two rows of horizontal red lights show the approximate power output of each channel.

Most of the NR-750’s front-panel controls are pushbuttons, which are used to switch power on or off and to select the input source, tape-monitor status, frequency band, FM muting or mono mode (when the muting is disabled), loudness compensation, infrasonic filter, and speaker connections. Two light-pressure buttons scan the tuner up or down in frequency if they are held in or change the tuning in discrete steps if they are pressed momentarily. The bass and treble tone-control knobs are neither detented nor provided with clearly visible index marks. A large volume knob and a small center-detented balance knob complete the front-panel controls. There is also a front-panel headphone jack.

The rear of the receiver contains the various input and output jacks, binding posts for the speaker outputs and the antennas (300- and 75-ohm FM inputs and an AM long-wire antenna), and a pivoted AM ferrite-rod antenna. One of the two a.c. convenience outlets is switched. The Nikko NR-750 is finished in black, and it has black knobs and buttons and white markings. Dimensions are 17-1/4 inches wide, 12 inches deep, and 3-3/4 inches high; weight is 16-1/2 pounds. Price: $250.

Lab Tests

The FM tuner section of the Nikko NR-750, like that of many other receivers we have tested, had a fixed tuning-frequency error of about 30 kHz. The error increases the tuner’s distortion, particularly at low signal levels, and thus degrades its usable-sensitivity measurement. Although the FM distortion in mono was low (0.1 percent, as rated), the stereo distortion was considerably higher than the specified 0.2 percent. The signal-to-noise ratio, however, was close to the rated value for both stereo and mono operation.

Most other tuner measurements were good, especially the capture ratio of 1.1 dB, AM rejection of 63 dB, and image rejection of 73 dB. The 19-kHz pilot carrier was present in the audio output at a rather high level of —46 dB, which should cause no problems with normal operation of the receiver but makes it imperative that any tape deck used with it for recording FM stereo transmissions have an effective 19-kFIz filter (as most do).

The FM frequency response was flat within 0.5 dB from 60 to 10,000 Hz and down 3 dB at 30 and 13,000 Hz. The stereo channel separation was good, between 30 and 40 dB from 30 to 8,000 Hz. The AM tuner section’s frequency response rolled off gradually below about 150 Hz and more rapidly above 3,000 Hz.

Measuring the receiver’s audio frequency response was complicated by the nearly invisible markings on the tone-control knobs. We set the knobs as closely as possible to their center positions, and the resulting frequency response was down 2.5 dB at 20 Hz and 2 dB at 20,000 Hz. The subsonic filter appeared to have a 6-dB-per-octave slope, and the response with it engaged was down an additional 2 dB at 20 Hz. The tone-control curves were good, with little effect on the middle frequencies and a moderate but adequate control range at the frequency extremes. The loudness control boosted the low frequencies, below 300 to 400 Hz, at levels 20 dB or more below the maximum volume setting.

The power-amplifier section had low distortion, typically 0.01 to 0.03 percent, over practically the entire audio range at rated power or less. The only exception was at 20 Hz, where the rated power (48 watts) could not be delivered without clipping. However, the full-power distortion was only 0.029 percent at 30 Hz. The amplifier drove 4-ohm and 2-ohm loads well, although its protection system shut it off momentarily when we exceeded 45 watts into 2 ohms. With the 20-milli-second tone bursts of the EIA dynamic-power tests, the amplifier was able to deliver 90 watts to a 2-ohm load.

Comments

We found the Nikko NR-750 to be a very satisfactory performer. Although it is not reasonable to expect a $250 receiver to deliver the same performance as one costing two or three times its price, the NR-750 comes surprisingly close to doing just that. Its control flexibility should satisfy almost anyone, and it is easy to use, attractive, and compact. It also sounds fine. Most people who are looking for a receiver in this price range should find its power output more than adequate, as we did using several different speaker systems.

The receiver’s instructions advise that unplugging it for more than six days may cause its preset station memories to lose their information. We left it unplugged for more than a week, and all the station memories were retained. Each time the receiver is turned on, the tuner is set to the last frequency played.

During our tests of the NR-750, we encountered no unwelcome surprises. Our only significant criticism concerns the essentially unmarked tone-control knobs. Actually, however, any product for which this is the major criticism must do a pretty good job!

Read all

Nikko reviews

Read all