The Cellar - View Single Post - New class-T amplifier?

wst3 · 09-30-2005, 02:37 PM

I don't know, but I sense some snake oil here! I read their white paper, and they make some interesting claims, and present some interesting measurements.

I could pick nits all day, but when people start claiming to measure total harmonic distortion (THD) with an excitation signal greater than 10 kHz I hear alarm bells. If the device or the test set is band limited, as the graphs indicate, then it is meaningless to measure THD with an excitation signal higher than 10 kHz since the first harmonic that you can measure is 20 kHz. If one is making a true THD measurement, the figure necesarilly decreases as excitation frequency increases. If, on the other hand they are making a THD+N or SINAD test (two common alterntives to THD) then it becomes just plain meaningless, since the noise will be much greater than the harmonics generated.

That's one example<G>...

I wish they'd provide a little more detail about just what "Class T" amplification is, I am curious. Like many I've built Class A, Class B, Class A/B, and Class D amplifiers, and even with common components (OK, can't really do that with Class D), they all sound different.

From their own information it is still a switching amplifier, although to be fair PWM may not be the best approach to switching amplifiers, and mixed mode technology has grown tremendously, to the point where the dividing line becomes blurry<G>!

I'd like to hear (and even measure) one of these things. I find it possible that the little amplifier may sound great. I agree with Silent that they may discover some challenges as they ramp up the power handling capability, both for the chip and the final product.

A also find some of the claims in the Forbes article to be a bit odd. But then there are audiophiles who spend $500 on a power cord and then claim to hear the difference.

Interesting stuff though...

09-30-2005, 02:37 PM	#4
wst3 Simulated Simulacrum Join Date: Jan 2001 Location: Pennsylvannia Posts: 39	Class T Amplifiers... I sense smoke I don't know, but I sense some snake oil here! I read their white paper, and they make some interesting claims, and present some interesting measurements. I could pick nits all day, but when people start claiming to measure total harmonic distortion (THD) with an excitation signal greater than 10 kHz I hear alarm bells. If the device or the test set is band limited, as the graphs indicate, then it is meaningless to measure THD with an excitation signal higher than 10 kHz since the first harmonic that you can measure is 20 kHz. If one is making a true THD measurement, the figure necesarilly decreases as excitation frequency increases. If, on the other hand they are making a THD+N or SINAD test (two common alterntives to THD) then it becomes just plain meaningless, since the noise will be much greater than the harmonics generated. That's one example<G>... I wish they'd provide a little more detail about just what "Class T" amplification is, I am curious. Like many I've built Class A, Class B, Class A/B, and Class D amplifiers, and even with common components (OK, can't really do that with Class D), they all sound different. From their own information it is still a switching amplifier, although to be fair PWM may not be the best approach to switching amplifiers, and mixed mode technology has grown tremendously, to the point where the dividing line becomes blurry<G>! I'd like to hear (and even measure) one of these things. I find it possible that the little amplifier may sound great. I agree with Silent that they may discover some challenges as they ramp up the power handling capability, both for the chip and the final product. A also find some of the claims in the Forbes article to be a bit odd. But then there are audiophiles who spend $500 on a power cord and then claim to hear the difference. Interesting stuff though...