NAD 118 digital preamplifier Page 2

In addition to its operation as a complete line-level preamp/control center, the NAD 118 has the following unusual features:

1) Digital signal inputs in addition to analog signal inputs. With digital sources, there's no need to use DACs. Analog and digital sources are handled identically.

2) Digital tape input/output in addition to analog tape loop. Analog tape output is available, unprocessed, from the analog inputs; or, via the DSP, from both analog and digital sources. Digital tape input and output are also available, but monitoring is possible only if the recorder has a DAC; the 118's monitor (Tape Check) circuits are entirely analog.

3) Digital signal output in addition to analog output. The 118 has a coaxial (RCA-type) S/PDIF output that permits you to substitute your own DAC for the on-chassis DAC.

4) A wide array of digital signal processes. This, the heart of the 118, includes a number of interesting and potentially useful DSP modes. In the standard, Tone Control mode, the controls are fixed in frequency but have variable boost and cut. At these frequencies, the bass (40Hz) and treble (10kHz) controls modify mainly the frequency extremes and have minimal effect on the rest of the spectrum. Hence, one can use these controls more liberally than ones at, say, 100Hz and 4kHz. The midrange frequency (2.8kHz) is set exactly where the average ear is most sensitive, and tiny adjustments are easily audible. I found a small boost with this control most useful in increasing the intelligibility of spoken voices, particularly with the BBC dramas rebroadcast by NET.

A related mode substitutes a fixed Infrasonic filter for the bass control while retaining midrange and treble adjustments. This is a quite effective function for eliminating LF noise, as it implements a steep cut beginning at about 24Hz. While I could dial in an effective equivalent with the rdp-1, the 118's Infrasonic filter was much simpler to use. The tradeoff, of course, is that the 118's filter supplants the Bass control, and thus you are unable to shape the musical range at the same time.

The FM mode lets you vary the channel separation from full stereo to full mono. Since the noise and hiss on FM broadcasts is usually out of phase between the two channels, channel blending minimizes it. As it reduces separation, the 118 applies a synthetic stereo algorithm. I found this mode to be useful for poor FM signals. Switching my tuner to mono or an intermediate blend mode was as effective in reducing noise, but, with the variable control of the 118, I could retain as much true separation as the noise would permit in all but the worst situations. The synthetic stereo effects were subtle, restoring a bit of spaciousness that was, at times, appreciated.

The Width control purports to be able to reduce excessive separation and to expand the width of some minimally separated stereo recordings. (It has no affect on mono recordings.) It is useful in minimizing the "hole in the middle" of very early stereo recordings, but only at the expense of some intended effects. Thus the 118 took all the fun out with "ping-pong" demo discs; but with some older classical recordings (eg, some of the early Westminster stereo LPs), a greater sense of presence and weight was gained. Rotating the control the other way to increase Width was effective in replacing the clumpy, center-weighted image on Mravinsky's recording of Shostakovich's Symphony 8 (Philips 422 442-2) with a semblance of space and air, but this function was usually less satisfactory because the separation was achieved at the expense of instrumental delineation.

The Width & Spread mode is similar to the Width mode, but adds a variable Spread function intended for mono sources. Starting with a decent mono recording and the consequent phantom image of all the instruments crisply fixed midway between the speakers, careful tweaking of the Spread and Width controls created a more spacious stage, and, with a little help from recorded phase anomalies and asymmetries in the listening room, a suggestion of instrument distribution. I did not find this mode especially useful, though, and great care was required to not destroy coherence. Don't push it, or everything will become vague and the center will not hold.

Finally, the 118 has Compression mode, which affects the dynamic properties of the sound. Increasing the degree of compression (turning the control up) raises the level of quieter sounds without affecting the louder ones. This reduces the dynamic range and is useful for very-low-level listening, or for making recordings to be auditioned in noisy environments such as an automobile. While this is a major musical corruption, it definitely has its uses. The 118 is also capable of expanding the dynamic range by reducing the level of softer sounds, but this is limited by the noise levels in the source. I've found it convenient and effective for radio (and DMX) broadcasts that have been subjected to dynamic limiting.

Despite my less-than-effusive praise for each of these individual modes, together they constitute an imposing battery of weapons with which to battle for better listening. Moreover, the 118 is capable of storing and recalling a particular DSP/Balance configuration for each input, and a preferred Setting/Balance for each of the DSP modes. And, with the flick of DSP In/Out, a flat response is always at hand.

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