The Truth about Modern Class D

The problem is not dead time, or notch distortion. The problem is audibility and connecting that to any particular technical choice.

Dead Time has nothing to do with notch distortion, but the chance exists that I mistook the gist of your comment.

It’s not false as Ralph would have you believe.

It is "also" a problem, but isn’t the "major problem", and the cause is of what many dislike what they hear in the upper/mids and highs which is a product of the switching noise and it’s associated filter.

It is believed that the dead time will also be vastly improved with a 3mHz switching speeds.

George, you've not thought this thru. You are correct that by increasing switching times you can decrease distortion. However, its not the filter that is an issue, in fact as the switching time goes up, there is a point where the inductance of the load is enough to eliminate the requirement for a filter!
(Usually the filter fails to remove all the high frequency component. This component is known as the 'residual' and if the filter is designed properly, will be a sine wave of low amplitude. As such it will not interfere with other equipment and is far too high to be heard!)
Now as you go higher with switching frequency, distortion goes down, but with any particular switching device- oh- I'm repeating myself; here's my comment that you apparently didn't read from above:

The problem is that dead time causes distortion. So with any given output device, there is always a certain minimum distortion and associated maximum switching speed.

Nelson's analogy is correct however, so imagine not having to wait for a transistor to shut off before the other one turns on! Now we can switch at much higher frequencies and with much less expensive parts. Alternatively, an amp with a lower switching frequency but no need for dead time can have distortion as low as an amp that needs the dead time and is switching considerably faster.

You might dislike the whole lot instead *Grins!*

Why? ... "BECAUSE!"

G.

It's simple G
As it stands now the switching frequency noise output filter, has phase shift effects that reach right down to 5khz, that doubled for the worse at 10khz and doubled worse again 20khz. That's what many listeners find objectionable, in the upper mids and highs.

If the switching frequency is moved much higher from the present 400-600khz to 2 or 3mHz, then the filter can be moved up accordingly. So it has no phase shift effects down to 5khz, but only then at over 20khz instead where it really doesn't matter.
And the dead time will magically improve as well, it's a win win, for higher switching speeds that's why Technics with the SE-R1 persevered to get it, at a cost rrp $30k aud. 

Cheers George

This has morphed into one of the more interesting and informative Class D threads I have witnessed.
I wish I had something technical to contribute myself but I do not, however that is why i peruse these forums, to increase my own personal database of knowledge.
But we do seem to have two diametrically opposed schools of thought of late, Switching Speed or Dead Time.
Now just what is an outsider supposed to believe here? How do I choose which path is best to follow? Does one wait for the various technologies to duke it out and see which becomes victorious.
Think VHS vs Betamax although maybe a poor analogy as the real winner did not win.
It seems Class D is ready to come of age if you like but in what way, shape or form?
Difficult choices ahead possibly

But you are reverting instead to your single track paper-bound comments

Only because of those "looking for confirmation" to what they think that Class-D is finally Hiend.
It hasn't changed that much since it's inception, many you will find are buying Chinese modules some modded via Pascal EU, just more and more trying to make "big bucks" out of what is essentially very cheap to make, if you take away the "glitzy chassis" they have.

NP: Personally I think it’s a miracle that they work at all. I am not tempted to go in that direction.    



Cheers George