The volume display on the front panel is fairly small and hard to read from across the room. In addition, the volume indication only appears when you make an adjustment and for a few seconds afterwards. Then it disappears until you make another change. The setting also changes by a step (0.5dB) whenever the Volume button is pressed. Since the display doesn't tell you where the level is set before you first command a level change, you have to remember this quirk if you want to get back to your initial setting. This common "change with first push" design is pet peeve of mine with many controls—audio and video—from a multitude of companies.

The tone controls, Center Dialog control, and the Audio Delay (lip sync) settings are volatile. That is, whenever you put the M15 in Standby or turn it off entirely, they automatically return to zero. While I can see some logic to this, it will be a nuisance for users who use the tone and dialog controls to compensate for speaker/room problems (in contrast to source problems) and the Audio Delay controls to counteract a fixed delay in their display's video processing. They will have to manually reset these controls whenever they turn the M15 off and then on again.

The maximum volume level may appear generous at +12 dB, but there will be times when it is insufficient. The most obvious current example of this is on the earliest Warner Brothers HD DVD titles, which were encoded about 8dB lower than the correct standard level.

M15: Upgradeability
The M15 can accept firmware upgrades through its RS-232 input. Future upgrades are possible via this route, though as with all products these upgrades must be compatible with the internal programming capabilities of the M15 itself.

But while the M15 is modular to a degree, it's not modular in the sense that an in-the-field swap of a board or two to install a major upgrade will be possible. Major hardware upgrades will require significant redesign, which is unlikely to be made available as a retrofit to existing units. For example, with regard to the switching issues mentioned above, it would take such a major hardware redesign to add HDMI audio.

M25: Outside and Inside
A power amp is the easiest component of all to describe if you stick to its external configuration and user interface. The NAD Masters Series M25 is no exception. THX certified. Seven channels. Seven single-ended inputs with seven pair of high quality speaker output terminals designed for use with bare wire, banana plugs, or spades. Buffered, low impedance level controls for each channel. Seven blue indicator lights on the front panel that cannot be dimmed, as is the case with the lights on the other Masters Series components. A 12V trigger that can power the amp up or down externally, which is a must in today's custom installation environment. Looks and construction quality that challenge products selling for two or three times the price. A Soft Clipping switch and Soft Clipping light.

Say what? If you're not familiar with NAD's products you may not have heard of Soft Clipping. But it has been a feature of NAD amps since before Reagan's jellybeans replaced Carter's peanuts as the favorite White House snack. When an amp is driven too hard, it generates distortion byproducts that not only sound ratty, but can also damage speakers. NAD's solution is to limit the overdriven waveforms in such a way that these problems can't occur. It's probably less of an issue with the 160Wpc M25 than it was in NAD's first amp- a 20Wpc, two-channel integrated design still fondly remembered by audiophiles who understand the peanut/jelly bean analogy. You can switch it off from the back panel (as I did for most of my listening with no apparent ill effects), but if you leave it on there's a Soft Clipping LED on the front panel that lights whenever it's activated.

The M25 also includes an NAD feature called PowerDrive. It's a refinement on the company's Power Envelope circuit (also used in their amps since way back). It entails a second high-voltage rail in the power supply that switches on whenever the demand requires. According to NAD, this doubles the available power above the continuous rating for a short period, allowing the amp to handle the overload without complaint.

Internally, the design's power supply consists of a single massive toroidal transformer along with multiple 100,000-microfarad capacitors. Each of the seven channels is built on its own removable module. There are no options on the number of channels, so the only reason you might want to remove a module would be for service. But the ability to service the rare errant channel in this 98 lb. amp without hauling the whole thing into the repair shop should not be minimized! The amp also has internal cooling fans. These are designed to come on only during high demands and shut off during low level passages. While I wasn't bothered by fan noise during most of the review period, in the last week or so the fan has come on more aggressively, and is audible from six or so feet away in a quiet room, and even while nearly quiet program material is playing.

The Masters' Voice: Music
This review was originally scheduled to include the NAD Masters Series M55 universal disc player. But I encountered a few glitches in our sample. A second sample is expected soon. The M55 will be discussed in more detail in an upcoming, separate report.

But none of the problems with the first M55 sample involved either its the audio or video quality, both of which are uniformly exceptional. That is why you will see it referred to below. I used it for much of my music listening tests for this review and, to a lesser extent, my standard definition movie watching as well.

The overall Masters Series system—the M55 universal disc player, M15 surround preamp, and M25 amp—sounded superb on two-channel music from my favorite CDs. It had a lively immediacy in the midrange that opened up a wealth of detail without going over the edge into aggressiveness, a full-bodied but not muddled midbass, a powerful low end (a powered subwoofer was used in the reference system), and wide-open highs. The top end of the system was less silky and delicate with the M55 player than with the Pioneer DV-79AVi, and less forgiving of dicey source material, but with the NAD player in the system the overall sound was more incisive, more dynamic, and simply more "there." The soundstage was as wide and deep as the music and recording demanded, and the imaging was rewardingly precise.

The system handled my favorite reference recordings with compelling ease. I've used the now ancient Gordon Lightfoot album, If You Could Read My Mind as a reference for pop male vocals for longer than I can remember. This was the best sounding Reprise album the singer ever released; his later albums were overprocessed and artificial sounding. But while not every cut on this CD is pristine, on the best of them Gordon's voice sounded clear and open over the NADs, with a natural warmth and timbre.

On Leo Kottke's album That's What, Leo's guitar sounded pristinely detailed, with all the delicate fingering as intact as you might expect from a closely mic'd but very clean recording. Kottke's gritty vocals were also rendered with all of their sandpapery textures intact. In a recording offering very different challenges to a system, the wildly varied percussion, vocals, and stunning acoustic ambience in Dead Can Dance's Into the Labyrinth were mesmerizing. The recording was made in a highly reverberant church, a fact clearly evident on playback, particularly on Lisa Gerrard's a cappella solo, "The Wind that Shakes the Barley."

The NAD M55 is one of the few universal disc players that will properly play back HDCD. The depth and naturally mic'd space in Reference Recordings' HDCD release of the Rutter Requiem kept me in glued to my seat.

I briefly auditioned NAD's EARS surround simulation mode. It was reasonably effective, but the calibrated surround levels were too loud in this mode and I had to drop them down by several decibels. The same was true of Dolby Pro Logic IIx Music. Ultimately, I preferred to listen to two-channel recordings without any simulated surround processing. But if you like it, it's there for you.