Class D is just Dandy!

It is the notion that Class D switching speeds are the cause, and that someday they’ll be fixed that irritates me.

If you guys are going to point a finger, get the whole story right.
It’s not the switching speed per se, but the output filter that has to try to get rid of it without any detrimental effects down into the audio band that’s the problem.
  
That’s why Technics with their $20k SE-R1 class-d has striven for double the switching speed, so then that output filter can do it’s job properly without much detrimental effect down into the audio band.

Cheers George

George, its more complex than that.

The reason Technics is switching so fast is to reduce distortion. The filter has little to do with it. At their speeds, the inductance of the speaker is sufficient. So their filters are mainly concerned with preventing RFI.

Keeping the switching speed high is important for resolution, and decreases distortion. The problem is that the faster you switch, the more time has to be alloted to allow the devices to turn off before its mate can be turned on.

This waiting time is called 'dead time' and increases distortion. so there's a bit of a catch-22: the more you try to decrease distortion by increasing switching speed, the more dead time you have to have and that increases distortion.

Technics' solution is by using Galluim Arsenide devices that no-one else can get, which are a lot faster (and can switch considerably faster than they are actually being switched in the amp). The reason they are doing this is to minimize dead time, and so have created one of the lowest distortion Class D amps made.

We're taking a different approach. We found a way to eliminate dead time altogether. This allows us to switch at a lower speed and still get lower distortion, or switch at a speed Technics is doing it, without having to use devices that are as fast.

" It's interesting how some defenders of Class D amps go to such lengths to classify the critics of these amplifiers as a minority, yet then go on to claim that the critics are prejudiced. Hmmm ...  "

Hi cleeds,
     Sorry, I'm not understanding your point.
     I really didn't go to great lengths to classify the class D detractors I've  read responses from since I became interested in this technology about 5 years ago.  Just a few minutes recollecting, a few classifying those I recall from Audiogon and other forums and a few minutes detailing my thoughts.
     In retrospectively considering and gauging the totality of posts I've read about class D in the past 5 years, I have little doubt that supporters of class D are in the majority and detractors in the minority. 
     I have no doubt that various forms of bias were evident in many of the class D detractors' posts.  Here are some of the major forms of bias I recall:
1.  Bias in the form of claiming class D was only good enough for subs even though they'd never auditioned a good recent class D amp in their system. 
2. Bias in the form of claiming their current amp would outperform a class D amp even though they'd never actually auditioned one in their system.
3. Bias in the form of claiming the majority of class D amp's switching frequencies  were too low and negatively affected sonics in the audible range even though they provided no scientific or even anecdotal evidence to support their claims.
4. Bias in the form of claiming class D amps were inferior because the Damps they auditioned in their systems failed in their opinion to outperform their much more expensive tube or class A existing amp.

    There are more forms of bias I recall but I'm short on time right now.  
    Yes, I do consider class D detractors overall a minority and do consider many of their posts I've read over the past 5 years to be biased in some form.
   Your stating this and adding a "Hmmm..." does not amount to a coherent statement.  Please clarify.

Thanx,
  Tim   

If bias was a disqualifier, these forums would be dead quiet.

George, its more complex than that

You keep saying it Ralph, it’s the main cause for me, and even noted SS amp manufacturers like the highly regarded Solution amps deigner/owner ect.

"Cyrill Hammer (Soultion Amps) "if you want to have your product performing at the cutting edge it is not possible with today's known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."

I know your developing your own Class-D around present day technology.
We all know hiend isn’t how it used to be, and we all have to do what we can to make ends meet.
I wish you luck on your venture into Class-D, but to me and others like Cyrill it’s too soon yet to take the plunge.

Cheers George