NAD 118 digital preamplifier Page 3

How to Evaluate the Sound?
The 118's versatility can be employed in several ways. First, as a complete analog in/out preamp, it works as a line-level preamp controller in a standard audio system. Second, as a digital-in/analog-out preamp, it functions as a system controller and DAC for an all-digital system. In addition, an external DAC can replace the 118's built-in DAC. Note that the DSP engine is always in the listening circuit because the gain and balance controls are always operable. This also means that the DSP In/Out button is merely changing the processing algorithm to one that affects only gain/balance. Thus, switching DSP In/Out is not a bypass of the processor.

As a complete analog preamp/controller, the 118 was lively and dynamic. The preamp exhibited no real nasties, and sounded for all the world like a decent analog preamp. The soundstage was neither as wide nor as deep as with my Klyne 6.3.3p or Sonic Frontiers Line-2, and the 118 seemed just a bit tinkly in the treble. Bass was excellent, but with a little less "slam" than expected. Actually, such performance, though not outstanding, is quite amazing when you remember that the signals are subjected to ADC, DSP, and DAC processing.

Replacing the 118's DAC with an external one was a significant step in the right direction; I tried the Audio Alchemy DAC-in-the-Box and DDE 3.0, Parts Connection Assemblage DAC-2, and the Uther 3.0. Overall balance of the 118+DAC-2 was excellent, with "slam" restored. Depth was improved, and only the lack of width and a slight veiling in the upper midrange distinguished the combination from an all-analog pathway. With the Uther there were minor improvements in clarity, but I suspect that here I was coming up against the limiting performance of the ADC. As a purely analog preamp, the 118 was a quite satisfactory performer, but one that I'd have a hard time recommending: unless the user prizes the DSP capabilities, it can not justify its price. Adding a superior external DAC is warranted by the improved performance, but also adds to the bottom line.

The 118 was a stellar performer with digital sources. In my bypass tests, the 118 was set for unity gain (by voltmeter), and the S/PDIF output from my Audio Alchemy DDS•Pro was connected directly to the Uther DAC, or via a loop through the 118. Matched Apogee Wyde-Eye cables were used to minimize cable effects. With the external DAC, it was difficult to detect whether the 118 was in-circuit except on immediate switching. The only difference was a very slight but consistent compression of the depth and width of orchestral images. Small groups and solo voices were unaffected. Indeed, extended musical listening sessions were a delight, and the minor faults disappeared into the general enjoyment of both the music and the great convenience and flexibility of the 118. Without an external DAC, the soundstage compression and tinge of HF brightness returned; still, they were noticeable only on switchover, and were not troublesome with extended listening.

Thus, with either analog or digital sources, the 118 benefited from being mated to a congenial external DAC with decent line-driving ability. (The 118 will not pass decodable HDCD signals even with a compatible DAC.) The only real bugaboo is that the digital output signal is subject to interruption with input switching and, depending on the muting ability of the DAC, you may hear switching transients. With the DAC-2, for example, these were plainly audible but not disconcerting. The fault is not entirely NAD's, as other DACs were unruffled by the switching.

Although most of the test listening was done in my main system, long-term (and, boy, do I mean long-term!) listening was done with the NAD in my weekend system. Here the 118 was fed by a Pioneer CD transport, DMX receiver, and analog audio from cable TV, and it drove an Assemblage DAC-2, BOW Wazoo amp, and a pair of Paradigm Esprit bipolar speakers.

Sheer delight. The speakers needed no help for themselves, but the sources often demanded the talents of the 118. DMX signals vary considerably, and the Width/Spread functions were effective on some of the mono-sourced selections on the blues and oldies channels. TV audio is often horrible, but the 118 could tame almost anything. For the first time, I could enjoy those wonderful opera performances on A&E that are so often hooty and hollow, and I could put some presence and kick into the House of Blues broadcasts. As for CDs, there are quite a few whose frequency extremes need a bit of tweaking; the 118 did that without destroying the musical integrity of the midrange. It was wonderful to be able to get more out of those signals, and it certainly was addictive.

Was it worth it? You bet. The combination of the 118 and the DAC-2 (or better DAC) gave me a nearly transparent and immensely flexible control center. While you might get more transparency for the same (or fewer) dollars with straight-line analog preamps, such transparency may not be enough when the source itself is far from perfect. The 118 let me improve the quality of the less-than-perfect sources with which we all live, and which, by Holt's Law, contain the best music.

The NAD 118 and the Z-Systems rdp-1, in their quite different ways, successfully bring DSP into high-end audio. Although both perform best in all-digital environments, each has different target users. The NAD, preferably with an external DAC, presents the same interface as traditional preamps and will appeal to those who want flexible control but prefer not to think about such quantities as frequency and Q. The rdp-1 requires an external DAC and demands that the user be analytical and precise with it. Each is a rewarding device, but my heart lies with the rdp-1.

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