Class D, or switching, amplifiers have been widely accepted in the professional studio and touring realms. Inherent in a Class D design for amplifiers is higher efficiency (or less heat), as the amplifiers are only "switched on" when there is music coming in from the input signal. So there is less need for large, heavy, and often costly heat sinks. For high-end home audio and home theater, though, they have traditionally been found mostly as built-in components to powered subwoofers, where large bass drivers can leverage the greater power output that a Class D amp offers. Many consumers and manufacturers have been hesitant to adopt Class D amplification, citing some of the issues with sound quality that plagued many of the early designs. More recently, pioneering companies such as Anthem (Statement M1) and Mark Levinson (No. 53) have successfully launched switching amplifier products into their premium lines.
Musical Fidelity, a British manufacturer known for money-no-object mono-block amplifiers like the Titan and pure Class A AMS amplifiers, has been actively building up its entry-level M1 product line, which includes the M1PWR, a Class D switching amplifier based on the Bang & Olufsen Ice Power module design. The M1 products give little indication that they are part of the entry-level line in the family, featuring beautifully machined metallic enclosures and sleek lines. The M1PWR weighs in at a little over eight pounds and retails for $1,300, although recent prices through authorized dealers have been seen for under $500.
To test the M1PWR, I kept everything in my setup the same, with the Oppo BDP-105 as my source for movies and music and my Parasound Halo JC2BP for a preamp. Substituting the M1PWR for my reference Crown XLS-2500 amplifiers (which incidentally are also switching amplifiers, although the topology is a proprietary design by Harman, rather than the B&O Ice modules) to drive my Salk Signature Soundscape 12 speakers. I first ran one M1PWR amplifier in stereo mode. I painfully ran through all of my standard reference material for music and movies. I say painfully because the experience was far from enjoyable. Dynamics were collapsed. The soundstage shrank to a small, short, flat rectangle slightly forward of my speakers. The ambience cues I normally get, which let you "see" the recording venue - be it a symphony concert hall, small intimate club, etc. - all but disappeared. Music sounded almost flat and lifeless, and the noise floor was rather high as well. I couldn't hear the usual tape hiss, microphone feedback, reverbs, and other small details I expected to hear on some of my reference tracks. The manufacturer claims a signal-to-noise ratio of 95 dB in stereo mode, which is right around the maximum dynamic range of the RedBook CD format. I will say that there was something sweet and a little warm about the midrange.
Luckily, I read the specs on these amps beforehand, which are rated at 65 watts per channel. I had an idea this would not be enough to drive my power-hungry speakers ... at least not to THX reference levels. I therefore asked the manufacturer to send me two M1PWRs, so that I might use its mono bridged mode feature. I didn't want to penalize the amp without testing whether this was a matter of the sound's character or just that it wasn't enough power. In mono mode, the M1PWR almost doubles down into 100 watts per channel into eight ohms (200 into four).
Click on over to Page 2 for the High Points, Low Points, Competition and Comparison and Conclusion . . .