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This might be important to some, while classD produces less heat, it is not necessarily so much more efficient that it's worth really getting excited about compared to all other amp designs.
Noise level of the amplifier does not exceed the -90 dB ceiling, and this is a good result, as well as 112 dB dynamics. The frequency response (Figure 1) extends from 10 Hz with a barely noticeable drop to 100 kHz, at this frequency the level at 8 ohms is -2.1 dB, and at 4 ohms -2.3 dB. In the spectrum of distortions (Fig. 2), apparently the third harmonic can be seen, reaching -72 dB, further shows the fifth and seventh, but already significantly below -90 dB.
Fortunately, the distortion in the midrange was predominantly the relatively innocuous third harmonic (fig.7), though at low frequencies the second harmonic was equal in level to the third (fig.. But note the very low level of all distortion harmonics in this graph!
Pass Labs specifies the XA25's output power as 25Wpc into 8 ohms and 50Wpc into 4 ohms (both equivalent to 14dBW). However, as you can see in figs. 4 and 5, the amplifier exceeded its specified power output at the clipping point, which we define as when the THD+noise equals 1%. At that THD+N percentage the XA25 delivered 80Wpc into 8 ohms (19dBW) and 130Wpc into 4 ohms (18.1dBW). It appears from the shape of the traces in these graphs that Pass specifies the XA25's power as when the THD+N is close to 0.01%.
I think in the Audio world today it’s more like 80% in the laggard bracket. Innovators and early adopters are generally frowned upon.
My 2 cents:"great amps" or at least those amps that are touted as great and have a rather large price tag to get all those Class A , AB watts etc...Along comes this Class D stuff and all of a sudden lots of us see a possibe device to get lots of watts at a great lower price..But the anti Class D folks pointed out all of its worts and negatives....Time moves on, Class D improves?? and now its getting to be in vogue?So I wonder if the Class D prices which were lower in comparison to the same number of watts back then now will climb up into the stratosphere...Just sayin....Alex:>)
Depends on the implementation. Bel Canto's Black range of components use Hypex modules and their prices are in what most most of us would consider the lower stratospheric range I'd imagine. Same with some of Jeff Rowland's gear. Consumers with cash to spare always want to find a way to distinguish themselves from the hoi polloi and there will always be entrepreneurs eager to satisfy that desire.
Its actually the price of admission that makes early adoption possible. Some spend more on cables and power cords than what some of these amps cost....
I'd be happy with a class D amp mounted on a piece of plywood if it sounds good. FWIW, I was an early user of class D amps starting with the Bel Canto S300 and the PS Audio Trio A-100 amps. These amps used the same ICE modules to get 100 or so watts into 8 ohms. The PS Audio had the gain cell input buffer and I liked it much better than the Bel Canto. Not going to list every class D amp I've owned, but there have been quite a few. I haven't heard the latest ICE modules, but have heard everything prior. My opinion is they always sound very good on initial listen. It's only after living with them for a while that I find them less than satisfying. My analogy is this: it would be like eating Snickers bars for every meal, after a while you feel somethings wrong with your diet. And I love Snickers bars.I'm sure at some point I'll try an amp with the newest ICE technology and hope it satisfies for the long haul.
