NAD 1600 Tuner/Preamplifier Review

A preamplifier/tuner is essentially a stereo receiver without a power-amplifier section. While such a component is smaller and lighter than a receiver, its principal advantage is the ability to drive any outboard power amplifier. High-power receivers, rated for 125 watts per channel or more, are very heavy and bulky, and they tend to run hot. With a preamp/tuner, you can use the most powerful amplifier you can afford, or even separate amplifiers for each channel—located out of sight if you prefer—while retaining the full control flexibility of a receiver in an attractive and compact unit. Also, upgrading the system at any time to a more powerful or better-quality amplifier is easy.

The NAD Monitor 1600 combines a high-quality AM/FM tuner and a preamplifier at a very moderate price. Although its specifications are excellent, our measurements showed that most of them are highly conservative.

The NAD 1600 has the styling and appearance of the company’s other Monitor Series components, with a gray panel and cabinet, black knobs and pushbuttons, and clearly legible white markings. A long, narrow black window across most of the front panel contains a number of pushbutton controls along with the display.

Most of the buttons in the window are tuner-preset selectors. The tuner has memories for fourteen stations, in two banks of seven. Each memory can be assigned to either an am or an fm channel; a button toggles between the two banks, and a light indicates the selection. Other buttons select AM or FM, mono operation (effective with any program source), and FM BLEND, which reduces noise in stereo fm reception by partially mixing the two channels. Unlike most other such circuits, the NAD blend circuit affects the entire audio frequency range instead of just the high frequencies.

The luminous display contains large station-frequency numerals, center-tuning indicators, a bar-segment signal-strength indicator, and a signal light that shows when a command is received from the infrared remote control. Unlike many receivers, the Monitor 1600 illuminates its tuner-frequency display only when the tuner is selected as the program source.

The tuning controls are two buttons to the right of the window. The search button below them selects either manual tuning (in steps of 50 kHz for fm and 10 kHz for am) or a continuous scan until a station is received.

The other controls form a row across the bottom of the panel. The volume knob, at the lower right, is operated by a small motor when the remote control is used. The balance control and the bass and treble tone controls are center-detented. A tone defeat button between the tone controls bypasses their circuits.

The program selectors are momentary-contact buttons. The available inputs are CD, video, phono, tape 1, and tape 2. A LOW level button next to the input selectors reduces the volume by 20 dB.

Two tape decks connected to the NAD 1600 can be cross-connected by a front-panel lever switch for dubbing from either deck to the other, and the tape-input selectors permit monitoring from either deck during dubbing. The EPL (external-processor loop) button at the lower left of the panel inserts a signal processor (or a third tape deck) into the signal path. Two nearby buttons activate the bass EQ circuit (a low-frequency boost affecting signals below 60 Hz) and a loudness-compensation circuit. Lights above the display window show when the EPL circuit has been selected and when a stereo FM broadcast is being received. The front panel also contains a power button and a headphone jack.

The supplied remote control is designed as a system control for other NAD components, including a cassette deck and a CD player. Many of the keys on the remote unit serve different (but analogous) functions depending on which source is selected. For example, the numbered buttons can select either preset stations, tracks on a CD, or recorded segments on a tape.

The rear apron of the NAD 1600 contains input and output jacks for all of the signal sources as well as the pre-out jacks that connect to a power amplifier. The phono-input jacks are gold-plated, and a small switch below them sets the preamplifier gain for a moving-magnet (MM) or moving-coil (MC) cartridge. Another switch activates an infrasonic filter that operates with all inputs, although it is likely to be required only when playing records.

There are two AC outlets on the rear apron, one of them switched, as well as a coaxial connector for a 75-ohm FM antenna feeder and spring connectors for a long-wire AM antenna and ground. Unlike most tuners, the NAD 1600 does not come with a loop antenna for am reception.

The NAD 1600 measures about 17 inches wide, 15-1/4 inches deep, and 4-3/4 inches high, and it weighs 14 pounds. Price: $399.

Lab Tests

The NAD 1600’s usable FM sensitivity, rated at 11 dBf, or 1 microvolt (μv) into its 75-ohm antenna terminals, measured about 12 dBf (1.1 μv). Radio-frequency measurements at these levels are difficult to make repeatably and accurately without a fully screened test room, and this problem was only too evident in our tests.

Data from NAD on our test sample showed an extraordinary usable fm sensitivity of 9 dBf. When we tried to verify this figure, we initially succeeded—to our surprise. But in later tests we were unable to repeat this result, possibly because of an increase in local atmospheric radio noise. Nonetheless, the 12-dBf sensitivity we measured consistently is still an excellent figure.

Much more important to the listener is a tuner’s 50-dB quieting sensitivity, and here the NAD 1600’s excellence was unambiguous. An input of only 15.5 dBf (1.65 μv) produced a solid 50-dB quieting level and truly usable listening in mono. The stereo threshold was 26 dBf (5.5 μv), and the stereo 50-dB quieting input was 38.6 dBf (23.4 μv). The tuner’s mono noise level was a very low —86 dB at inputs of 65 dBf or greater. The stereo noise was —75.5 dB at 65 dBf and - 80.2 dB at inputs of 85 dBf and higher.

The tuner's capture ratio of 1.3 dB and am rejection of 88 dB were excellent, and its 79-dB image rejection was well above average. Selectivity was 62 dB for alternate-channel spacing and 5 dB for adjacent-channel spacing, both good though not exceptional figures. The hum level was —79 dB, equally divided between 120- and 180-hz components. The 19-kHz stereo pilot-carrier leakage into the audio was at a -72-dB level, and the 38-knz stereo subcarrier was undetectable.

Frequency response in FM was +1.3, -0.2 dB from 30 to 15,000 Hz, and stereo channel separation was about 50 dB through the midrange, 39 dB at 30 HZ, and 29 dB at 15,000 Hz. The fm blend circuit reduced the channel separation to a constant 7 dB from 30 Hz to several kilohertz; the separation was slightly greater at 10,000 and 15,000 Hz (8 and 10 dB, respectively). Activating the blend circuit also reduced the overall program level by 3.2 dB. The am section’s frequency response was +2, - 6 dB from 23 to 2,800 Hz.

The NAD 1600's preamplifier section had a frequency response of + 0.05, -0.18 dB from 20 to 20,000 Hz. Its tone controls had conventional characteristics, with a maximum range of slightly more than ±10 dB at the frequency extremes. The Bass EQ circuit took effect gradually below 100 Hz, raising the response to +6.4 dB at 35 Hz and cutting it to -20 dB at 20 Hz. The loudness contours were conventional, boosting both low and high frequencies as the volume-control setting was reduced.

Total harmonic distortion plus noise (THD + N) at 1,000 Hz was just over 0.01 percent for outputs of several volts, and the output clipped at about 10 volts. At 1 volt, the distortion consisted of odd harmonics at very low levels, -90 to -100dB. The RMS sum of the first twenty harmonics was -86.5 dB, or0.0047 percent. At 5 volts, the RMS sum was -83.3 dB, or 0.0068 percent. The preamplifier’s A-weighted noise level was exceptionally low, - 86 dB for MM phono, - 81 dB for MC phono, and a remarkable -101.5 dB for the CD input.

Comments

The NAD Monitor 1600 is an unusual and noteworthy component, not because of its features, few of which are unique, but rather because of its excellent overall performance, which in several respects challenges the most advanced of today’s hi-fi products. Its FM performance was particularly admirable, at a level seldom attained by the most expensive receivers—or even by separate tuners in its price range.

The preamplifier section also performed superbly, at a level of distinction that would do credit to any separate preamplifier in this price class. The Bass EQ circuit can provide a useful deep-bass foundation—assuming your speakers are capable of it—without a trace of boominess. The phono stage was first-rate overall and absolutely outstanding in signal-to-noise ratio (S/N). In addition, the high-level section’s A-weighted noise level of -101.5 dB (referred to 0.5 volt) was possibly the lowest we have measured in a preamplifier and actually lower than the noise output from many CD players.

In everyday operation, the NAD 1600 was as simple and straightforward as one could wish, in sharp contrast to the control complexity of so many receivers. Even its remote control was surprisingly simple to use, especially considering that it is a system control designed to operate a cassette deck and CD player as well as the preamplifier and tuner functions. Its twenty-three buttons are grouped logically and distinguished by different colors. Nevertheless, it’s a good idea to read the complete, well-written instruction booklet carefully. For example, although switching from the tuner to a CD player or tape deck is a single-button operation, it is necessary to press two buttons to return to the tuner.

The NAD 1600 is not only an excellent preamplifier/tuner but one of the outstanding values in today’s hi-fi market. Its price would be quite reasonable for either a tuner or a preamplifier, and few products in either category at that price would be likely to match its performance. To get it all in one attractive package for $400 is remarkable. Combine the Monitor 1600 with a good separate power amplifier, from NAD or another manufacturer, and you could have a light, compact, cool-running “receiver” able to deliver upwards of 100 watts per channel for less than $1,000, with overall performance superior to that of any single-chassis unit in the same price range. By my standards, the NAD 1600 is a true bargain.

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