New Digital Switching Amplifiers

How do you define "filter out the HF switching noise"?

Just curious.

There are 2 kinds of noise:

One that goes out on the speaker leads at the switching frequency. We'll say in the 500 kHz range. (I believe Tripath and Nuforce may be closer to 1 Mhz.) The other is all the crud in the 60-100 Mhz region that will mess up TV reception ans some other things. Two different issues, 2 different solutions.

As for distortion changing with warm-up:

You can get the distortion to drop if you increase the "stand-by" current drain. Problem is, you run the risk of destroying the switching transistors if you get it too high. There could be a thermal change in that parameter in the unit under review.

No. There is no correlation to the switching frequency and input signal. If you took x number of any brand of "self-oscillating" amps, put them along side, they would all be different. The ones that I use will vary between 480 kHz to 510 kHz or so at idle.

The old style ones.......the ones that gave "digital" amps a bad name......used a fixed frequency oscillator. It remained constant.

I agree. I believe he is assuming that this genre of amps has not improved any in the last 20 years.

It has.......I wouldn't waste my time with them if they hadn't.

As for "conversion".........some types do. The PCM/PWM ones do. Mostly, they just modulate the power supply, which is all that any amp does to begin with. It is just a different form of modulation.

I do not understand how they "only transmit white noise". Waiting for an explanation on that one. RFI, yes they do produce that. Some of us go to great lengths to eliminate it.

As for "cheap". Yes, some are. About the only real cost eliminated is the heat sink. You can get by with a smaller power transformer, as you don't have to heat the atmosphere at idle. Other than that, they are not that much cheaper to build.

Well, the goods ones aren't........