NAD Masters Series M2 Direct Digital Amplifier Challenges Paradigms
May 22nd, 2009 -- by Chris Martens
Source: AVGuide
Source: AVGuide
Sharon, MA-based NAD Electronics today announced its new Masters Series M2 Direct Digital Amplifier—an amp whose circuit topology not only challenges many established paradigms, but that, NAD says, “sets new benchmarks for both measurable performance and subjective musical quality.” According to an NAD press release, the M2 “can be thought of as a Digital-to-Analog Converter (DAC) that directly drives a loudspeaker, but with the same precision as the very best low-level DACs.” The goal was for the M2 to become, “the first digital amplifier that can match the best linear amplifiers for low noise and distortion, delivering better than Class A sound with Class D efficiency.” The M2 is a stereo amplifier that can produce 2 x 250Wpc into 4 or 8 Ohms, with 500Wpc of IHF dynamic power on tap. The M2 will become available from NAD dealers this summer at an MSRP of $5999.
A Number of “Firsts”
NAD touts a number of “firsts” achieved by the M2 design, including these:
- First digital amplifier to provide “a fully digital signal path” (though both single-ended and balanced analog inputs are also provided, backed by what NAD describes as “a fully balanced, state-of-the-art analog-to-digital converter”).
- First digital amplifier to use “high-speed digital error correction to reduce distortion."
- First digital amplifier to “fully implement digital closed-loop processing (a.k.a. error correction).”
- First digital amplifier to “implement a new technology called Direct Digital Feedback developed by U.K.-based Diodes Zetex Semiconductors Ltd. during its collaboration with NAD on the M2 project.” The NAD press release explains that the M2 incorporates “a unique, custom implementation of Diodes Zetex's patented Direct Digital Feedback Amplifier™ (DDFA) architecture within a Xilinx field programmable gate array to provide a custom platform for blending DDFA technology with NAD's own innovations.”
.jpg "NAD M2: Rear Panel")
More Design Details
Unlike most power amplifiers, which provide analog audio inputs only, the M2 provides a much more varied and extensive array of inputs, including two sets of stereo analog audio inputs (single-ended and balanced XLR), plus five sets of digital audio inputs (two coaxial, two optical, and one AES/EBU). Moreover, in a sharp break with typical practice for most power amplifiers, the M2 provides “a DSP (engine that) is custom programmed with NAD's high-resolution digital volume control possessing a broad attenuation range and perfect channel balance.” The M3
One practical upshot of this design choice is that digital source components can be plugged into the M2 directly, obviating the need for a traditional preamp (though the M2 can accommodate preamps, if users so desire).
Interestingly, the M2 also provides “a five-position digital impedance compensation filter allows fine-tuning the top octave to match the selected speaker impedance, resulting in a perfectly flat frequency response at 20kHz.”
Finally, the M2 includes a “unique Digital Processor Loop(that)allows advanced users to insert external digital filters into the signal path.” NAD explains that one intended purpose of the loop is to allow PC and Mac users to access and apply wide libraries of available “crossover filters and room correction programs.”
The M2 certainly sounds interesting on paper; we can’t wait to evaluate the amplifier’s real-world performance once it is released later this summer. As the release date draws closer, watch for more information to become available at this site:
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Comments
Quite interesting. It would be particularly interesting to compare how this product performs against the products of the established pure digital amplifier manufacturers like TacT and Lyngdorf. Since pure digital power amplifiers are effectively DACs with enough current output to dirve speakers, a big part of the magic is in the DSP involved. Tact/Lyngdorf have used Equibit algorithms from Toccata (current onwned by TI) since their first digital amplifier. I tried to dig some info. on the web and on Diode Zetex website. However, information is lacking on how PCM is converted to PWM, what the switching speed is, what the minimum pulse width is etc. UnlikeTacT and Lyngdorf, NAD does not seem to use the powersupply output voltage to control volume but uses digital volume control. The feedback technique used seems similar to the one used by Spectron, I think.
I have been reading very good user feedback and reviews on the few pure digial power amplifiers available. I hope TAS would do comparative reviews or dedicate part of an issue to the current pure digital amplifier offerings and how they compare to the state the art in a normal playback chain . The technology is very promising particulalry for digital playback. Other than the need for a high quality power supply, the analog part of the signal path is extremely simple consisting only of the inductor and capacitor sitting right before the speakers and generating the analog signal from the PWM modulated digital signal, which is very minimal compared to the tens or hundreds of parts that the analog signal goes through in a DAC/preamp/amp setup. If the technology is as good as it looks on paper, it has the potential of getting high end to reasonable prices because the parts of a digital amplifier are rather few and there are few places in these parts where exotic components can be called for . Basically the parts of a pure digital power amplifier are a robust power supply, digital signal processing (the price we pay for this part is really for the know-how that goes in the digital filters and not for the cost of parts which is very little), a robust clock, the transistor switches and the reconstruction filter mentioned above.
Looks like another TacT or Wadia Power Dac. This approach (apparently) has limitations. One is decimation errors - although NAD looks like it "corrects" them. But at what cost ? Then the output stage, if it switches, there could be problems with RF. Class *A* output seems to be the best these days. Finally, the DAC. Can it be cutting edge when it has to do all these other things ? The TacT here was limited - the NAD may also be.......
This NAD piece looks great in many respects. DAC-amps are an "it's about time" thing, and the digital processor loop is a fantastic idea.
So where does it go wrong? At the very top. Two-point-zero channel audio just isn't relevant today, especially for people interested in the fringes of high technology. NAD puzzlingly didn't even devote any DSP horsepower to any kind of bass management, despite the fact that getting clean response below a typical domestic listening room's modal frequency is simply impossible with two speakers placed properly for mids/highs/imaging. Multiple subwoofers, carefully placed and tuned, are required for high-fidelity reproduction. So at a minimum, NAD should have allowed for that in their new $6000 box. And while they're going in that direction, may as well make it relevant as a centerpiece for a modern audio system by adding another five amp channels and native decoding for the relevant Dolby/DTS/Apple codecs.
Also, NAD is an Audyssey licensee. How cool would it have been for them to use this amp technolgy in a 7.4-channel box (seven amplified channels, four line level and maybe digital subwoofer outputs) with Audyssey's full technology suite?
Perhaps the goal is simply to get the 2-channel folks to beta test it before a wider release. I hope so, because a receiver like the one I described above would anchor my system in a heartbeat.
Nad is on the right way right now with the new digital stereo equipment. Who needs a lame home theater these days? I don't.
I'm yet to hear a better sounding multi-channel system than an equivalently priced two-channel rig.
Boy, could I make a 5.0 sounding dynaquad system out of this baby but it will never happen in my home. That's life.