New Class D amplifiers

Just came across this new review of the Technics SU-G700M2 from The Absolute Sound on YouTube:

It's nice to have this deep dive into the inner workings of this amp. He even goes so far as to say it's a taste of the Ultra High End for a tenth of the price. Not perfect, or everyone's cup of tea, but it's got the goods.

All the best,
Nonoise

@rsf507 

Not as yet. Still trying to follow this thread even though it seems to have taken on a life of its own. There are several I would like a chance to listen to first. Difficult to arrange.

D-Class are exceptionally good.  Lots of power, cheap. Here are two different reviews I did and are different prices.  One can be bought under $100, and the other around $600 as they Hypex amps.

And

@atmasphere: Your quote earlier:

There should be no difference at all! If you think there is, then you are convinced that we can't make the measurements for everything we hear (which, since about the early 1990s, we can) and also that the human perceptual rules that are shared by everyone on the planet are of no consequence, making things like deciBels irrelevant.

In the interest of my own learning, would you please point out which measurements correspond to what people hear? It would also be interesting to know how the type of measurement is performed and deemed to correlate to how our hearing works. Thanks.

In the interest of my own learning, would you please point out which measurements correspond to what people hear?

Sure- two measurements that have not got the attention they deserve- first, distortion vs frequency, which ideally should be a straight line or decreasing with increased frequency.

If the amp has problems with feedback due to insufficient Gain Bandwidth Product, the distortion will rise with frequency above a certain point (often between 1 and 3KHz). If this happens the amp could be perceived as bright due to how our ears perceive higher ordered harmonics and the Fletcher Munson curve.

The other measurement is the distortion spectra. Its not enough that the distortion be low. The ear has a masking principle; the way that tube amps sound nice and smooth is because they have enough 2nd and 3rd harmonic that those harmonics are able to mask higher orders. If those harmonics are insufficient, the amp may be perceived again as harsh and bright. This measurement is a bit open to interpretation as you have to know what you are looking at to be able to say how the amp is going to sound when you listen to it.

Quite often this last measurement is done with the fundamental at a low frequency - like 50 or 100Hz. If this is so and there isn't a measurement with the fundamental at 1KHz or higher then the measurement isn't all that helpful if distortion rises with frequency! IOW at a low frequency the distortion spectra might appear benign but above a certain frequency things could be considerably different.

So now you can see how an amplifier with 0.005% harmonic distortion might sound harsh and bright if those harmonics are not masked and the THD was measured at a low frequency- this can hide problems in the design. OTOH a zero feedback tube amp might have much higher distortion, but because it does not rise with frequency and the lower orders dominate, it might sound smooth and musical.

Class D offers a means to eliminate the first problem of rising distortion as well as allowing for a more benign distortion spectra.