Nikko IA-600 Integrated Amplifier Review

The Nikko IA600 is a powerful integrated amplifier, rated to deliver 120 watts per channel into 8-ohm loads from 20 to 20,000 Hz with no more than 0.01 percent total harmonic distortion (THD). The specifications also include dynamic power ratings of 170 and 270 watts into 8-and 4-ohm loads, respectively.

The multilingual instruction manual, although quite explicit concerning the installation and operation of the IA600 amplifier, provides no information on any of its circuit or construction features. It is however a rather large and heavy unit, measuring about 17-1/2 inches wide, 16-1/4 inches deep, and 5-3/4 inches high and weighing 32 pounds.

The front panel has two parallel rows of light-touch rectangular pushbuttons that provide independent selection of the program source for the audio (monitor) outputs and for the tape-recording outputs. A small LED in each button shows when that source has been selected, glowing green for the monitor program, red for recording. There are seven high-level inputs: CD, tuner, auxiliary, tape 1, tape 2, video 1, and video 2. The “video” inputs are actually conventional line-level inputs for the audio portion of a video program or any other comparable signal. The single phono input is switchable for a moving-magnet (MM) or moving-coil (MC) cartridge by a front-panel button. Another button inserts an external signal processor, such as an equalizer, into the signal path to cither the monitor or recording outputs (but not both simultaneously).

Similar pushbuttons independently connect the two sets of speaker terminals to the amplifier outputs. Both sets of speakers can be silenced for listening through headphones via the front-panel jack. Small round buttons parallel the channels for mono operation, switch the phono input for operation with an MM or MC cartridge, activate the “subsonic” (infrasonic) filter and loudness-compensation circuits, and reduce the audio output by 20 dB.

Small round knobs operate the bass, treble, and balance controls. An arc of green lights surrounding each knob shows its setting. A large volume-control knob is located at the right of the panel. Between it and the other controls is a small pushbutton marked CD DIRECT, which connects the CD input to the amplifier regardless of the setting of the monitor selector, bypassing all circuits except the volume control and — 20-dB attenuator. All the knobs have soft rubber rings that make their adjustment exceptionally easy. Those for tone and balance have light center detents.

The rear apron contains the signal input and output connectors, preamp-out and power-amp-in jacks (normally joined by jumpers), and the speaker terminals. Although the manual’s illustrations and text indicate that the speaker terminals are spring clips that accept stripped wire ends, our test amplifier was equipped with large binding posts. Unfortunately, they did not accept banana plugs. Two of the three AC outputs are switched. Price: $660.

Comments

As our measurements clearly show, Nikko has not skimped in the design or construction of the IA600. It feels (and is) heavy and solid, and its performance was consistent with those qualities. We were also pleased to find it about as '‘bulletproof” as an amplifier can be, although we made no deliberate effort to destroy it in our tests.

The controls operated with a smooth and positive action, although the balance and tone-control detents on our sample were sometimes difficult to feel. All the switches operated without any electrical or acoustic noises, reinforcing the impression of quality conveyed by the amplifier's construction and appearance. As with other products we have seen that have a similar feature the CD DIRECT mode was not measurably or audibly different from normal operation (at their flat settings the tone controls did not modify the basic amplifier performance in any way we could detect). But given the ambiguity of their center positions, being able to bypass the tone and balance controls might turn out to be a useful feature m this case especially for highly critical listeners

Although Nikko has been in the U.S. hi-fi market for many years, the company has been relatively quiet for some tune. If the IA600 is typical of its current products, we look forward to seeing some of the others.

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