Class D is just Dandy!

Wake up and smell the roses sunshine, Class-D is not as Dandy as you try to make out it is YET. I can quote many more just as esteemed as Nelson Pass if you like.

In the future with higher switching frequencies that look to be promised by the semiconductor tech-heads, it very well maybe the amp of choice, then our heavy, gas guzzling linear amps will become door stops or boat anchors.

Class-D today certainly has it's niche in audio, but it can't mix it with the real top of hiend yet.

Cheers George

Greetings One and All

So i fell across and have enjoyed reading this thread from page 1 - quite the hike. As an entry level audiophile with a passion for both stereo and home cinema and given the title of the thread I thought i'd chime in. Very much an enthusiast I have some basic understanding, have tweaked existing hardware replacing crossover components etc but do not pretend to understand some of the more advanced electronics principles involved in this discussion. I currently have a combination of class A/B and class D both in my car and home and have a mix of passive and active filters.

I don't expect to convince people looking for high end as up to now I have no experience in this domain but it is clear to me that class D amps are capable of some very serious sound and at specific price points can better other alternatives, this I believe is the common denominator for anyone interested in quality audio and the reason for my post.

I stumbled across and am very very pleased with my latest class D amp which happens to find itself inside a pair of floorstanders, admittedly a bit of an exception from most of this thread. I can highly recommend people investigate the Nubert active range, I'm currently running the Nu-Pro A-700

This is a fully digital class D implementation, so is digital up to the output stage, no DAC but a high end ADC for line in, it has the advantages of 3 way drivers with one amp per driver ( 2 x 90w mid and tweeter, 1 x 300W for the 2 woofers) phase correction and group delay as well as frequency response are managed by the onboard DSP.
 
There is a lot of technology at work here and I continue to be surprised by these speakers every time I listen. I took the risk of purchasing without listening base on reviews translated from a variety of German audio sites, one of which suggests there is currently no better active speaker under 10k€, class D or otherwise. at 2500 euros the pair they are worth looking into and there are other less expensive models built on the same principles.

Here's one of the reviews that show some of the guts:

http://mein-heimkinotest.de/standbox-revolution-fuer-2500e-paarpreis-die-nubert-nupro-a700/
(seems the link for the translated version gets cut short)

Thanks all for the very informative thread :)

Cheers
Phil

@georgehifi

And no one is more invested in making sure they know you don't like Class D than you are.

Best,

Erik

10 years ago class D had already been around for a while, but back then they weren't bringing home the bacon against the prior art. But it was obvious even ten years ago that it was a rising star.

In the last few years though its become a technology to be taken seriously. So about a year ago we began working on our own design.

Despite this, I can't call it a mature technology, a since price/performance curves define what is mature, and the technology is still improving at a rapid rate.

The major problem, as George points out, is the switching speed, but in recent years that is a problem that is fading. Part of the issue of switching speed has to do with the introduction of dead time, which makes distortion. But there have been a lot of advances in relatively cheap semiconductors recently, and the result has been that for a given switching speed, there is less dead time required because the newer devices are so much faster.

This means also that higher switching speeds are showing up.

Somewhere in this, a threshold is being crossed. We see this with the many responses on this thread. Class D, while like any other technology that has its better and worse executions, has arrived.

Its my opinion that any amp manufacturer that ignores the implications of class D is doing so at their own peril.

Looks like our first patent in the field will be filed soon...

Nice summary of benefits of GaN for class D implementations:
https://www.eeweb.com/profile/alex-lidow/articles/how-to-gan-egan-fets-in-high-performance-class-d-audio-amplifiers

Class D clearly has even more potential although given the article was written in 2014 I struggle to understand why this tech isn’t more prevalent today. Am curious to open my amps and check the components but given the heatsinks present I suspect it’s not based on GaN tech. In any case I smell the roses and class D has come of age.

Cheers
Phil