NAD 705 Stereo Receiver
The NAD Model 705, which falls in the middle of the company's receiver lineup, follows the NAD tradition of striving for high performance and functional design at a reasonable price. For example, all NAD amplifiers, whether separate components or part of a receiver, feature what the company calls Power Envelope design, which enables them to deliver outputs well beyond their continuous-power ratings during the brief intervals required by music peaks. Thus, despite its modest specification of 40 watts per channel into 8 ohms from 20 Hz to 20 kHz at less than 0.03 percent distortion, the Model 705 is also rated to deliver from 90 to 160 watts per channel into loads of 8 to 2 ohms during program transients.
The Model 705's front panel presents an uncluttered, functional appearance, especially in comparison with that of many other contemporary receivers. Finished in the attractive dark gray used throughout the NAD line, the front panel is adorned with three small knobs and two larger ones, plus a few well-marked pushbuttons and a headphonejack.
The small knobs are center-detented controls for bass and treble adjustment and channel balance. A slightly larger recording-selector knob connects the desired program source to the recording outputs on the rear apron. The largest knob, the volume control, is also motor-driven from the supplied remote control.
Like most modern receivers, the NAD 705 has a display window that shows its overall operating status. Large numerals indicate the tuned frequency and preset-channel number (as many as thirty-nine AM or FM frequencies can be stored in a nonvolatile memory for instant recall).
Small buttons below the display control most of the receiver's functions. A pair of white up and down buttons select the program source for listening. When either is pressed, the display presents the available inputs: phono, video, CD, tuner, tape 1, tape 2, and auxiliary. An arrow moves as the buttons are pressed, to show the selected source. After a few seconds, the labels for all but the selected source are extinguished.
When tuner is selected, the AM/FM button selects the desired band. The mode button offers a choice of search, manual, or "preset" operation, with the selection name displayed in the window for a few seconds. In search mode, a tap on one of the up/down tuning buttons causes the tuner to scan until it finds a receivable signal. Manual mode tunes in unusually fine 25-kHz steps on the FM band and selectable channel steps on AM, 10-kHz for North America or 9-kHz for most of the rest of the world. In preset mode, the tuning buttons step through the station presets. You can also enter any preset number or station frequency directly from the keypad on the remote control.
The remaining front-panel controls include buttons for independent selection of the two pairs of speaker outputs, mono/stereo switching, and loudness compensation. The speaker selection (A, B, or both) appears in the display window, as does a multisegment FM signal-strength indicator.
In addition to the various signal input and output phono jacks, the Model 705's rear apron has separate preamp-out and main-amp-in jacks, joined by removable jumpers. This arrangement offers added flexibility for inserting external processors (a surround decoder, for example) into the signal path or substituting other power amplifiers for those built into the receiver. A pair of jacks labeled Multi Room Output carries the selected program at line level, unaffected by the receiver's volume, balance, or tone controls. In a multiroom installation the signal can be fed to a separate amplifier for driving speakers in other rooms. Other "NAD Link" jacks enable creation of a true multiroom remote-controlled music system with other compatible NAD components.
The Model 705 also has NAD's Soft Clipping circuit, which causes the signal waveform to round off smoothly near the maximum power level, minimizing the harshness associated with peak clipping. This feature can be selected or defeated by a small slide switch on the rear apron.
There is a 75-ohm coaxial FM antenna input and a connector for an AM wire antenna. The main (A) speaker outputs are insulated binding posts that accept single or dual banana plugs as well as stripped wires. The B speaker terminals are spring clips that are usable only with stripped wire ends. One of the two AC outlets is switched.
The Model 705's FM tuner section had an outstanding capture ratio (important for rejection of multipath and other co-channel interference) and good AM rejection. Selectivity was only fair, however. The tuner had a very low hum level, and the 50-dB quieting sensitivity in mono was very good, although the stereo reading was less so. Stereo channel separation was better than 40 dB from 35 Hz to 2.5 kHz and about 27 dB at 15 kHz.
The FM frequency response was better than +/-0.2 dB from 20 Hz to 9 kHz and down less than 0.7 dB from 9 to 15 kHz. AM response was +/-1 dB from 20 Hz to 1.3 kHz and down 6 dB at 2.5 kHz.
In addition to our usual measurement of amplifier response from source input to speaker output, we also checked the preamplifier section's frequency response alone, measured at its output prior to the power-amplifier section. It was a good +/-0.2 dB from 25 Hz to 20 kHz and was down less than 2 dB at 200 kHz. The tone controls had good characteristics, with a sliding bass-turnover frequency from approximately 100 to 400 Hz and treble curves that hinged at about 2.5 kHz. At reduced volume settings the loudness compensation boosted the lows (below 200 Hz) by a maximum of 10 dB and the highs by a maximum of 3 dB at 20 kHz.
The amplifier's power delivery fully lived up to NAD's claims. At a constant 0.1 percent distortion into 8-ohm loads (with both channels driven), the power output was between 48 and 52 watts per channel from 20 Hz to 20 kHz. Under the same conditions into 4 ohms (for which the Model 705 is not specifically rated), the power ranged between 53 and 55 watts from 20 to 800 Hz, reached 61 watts at 1.2 kHz, dropped to 53 watts from 3 to 8 kHz, and climbed back to 61 watts at 20 kHz. The 1-kHz distortion into 8 ohms at the receiver's rated 40 watts was 0.03 percent in one channel and 0.04 percent in the other.
But where the Model 705 really showed its mettle was in our dynamic power measurements, which use a 20-millisecond 1-kHz tone burst repeated at half-second intervals. Into loads of 8, 4, and 2 ohms, the output clipped at 95, 144, and 263 watts, respectively, easily surpassing NAD's specifications. Very impressive for a "40-watt" amplifier!
The NAD 705 was every bit as exceptional in use as it was on the test bench. From the first look, we felt its simple, uncluttered appearance was a vast improvement over that of today's typical receiver, so often studded with pushbuttons and an overloaded, confusing display panel.
Even simplicity can be confusing, however, when it's different from what you've become accustomed to, and that makes a study of the instruction manual as important as it would be for a full-blown audio/video receiver. Fortunately, NAD explains the receiver's operation clearly in a few pages, and after a short familiarization its true merit becomes obvious.
My most serious reservation about the Model 705 concerns its display window. The problem was not its content (it's perhaps the best I have seen in that regard), but its dimness and lack of contrast. Unlike the typical receiver display, dazzling in its bright, multicolor splendor, this one is too dim to be read easily in a normally lit room, at least from more than a few feet away. Also, unless it is viewed straight on, the upper part of the display is masked by the panel, preventing you from seeing which speakers (if any) are being driven.
Since that minor and perhaps idiosyncratic criticism is the only one I could come up with after living with the receiver for some time, it is only fair to say that the Model 705 is everything NAD claims for it and a lot more receiver than its modest size, price, and appearance would suggest-a worthy new member of a long line of distinguished products.
