Class-D amps - a different re view

Atmasphere, class D has, in fact, secured the boombox audio field for the very attributes you listed. That says nothing of the class D amps that have been designed for the 2 channel audio connoisseurs, anymore that the previous mass product use of tubes defines your products.

The most fussy tube amp I have heard is the Audio Note Kageki. As I understand AN takes pains to limit compromises for their upper shelf amps.

ICE makes the 500A amp module. This is a module that requires an add on power supply, unlike the ASP modules that have digital power supplies built in.

The 500A module is aimed at the tiny audiophile market. You'd think that would be it. No, they spent countless engineer hours improving the 500A module. You may consider this production in agreement with your reduced compromise ideal. Why did they do that? They wanted to limit compromises in their finest module.

Now, the 500A module's amp performance depends on that amp designer's talent and knowledge. And better sound doesn't stop there. That designer amp's performance depends entirely on it's owner's application. I have found the requirements of a successful class D system are stringent indeed.

The better of class D amps CAN be frightfully outer space transparent. The down side is any, whether it be electronic, like oversampling DACS, or physical, like hose speaker cables, the result can be disastrous. That has been my experience.

So y'all understand, just because I make tube amps, that does not mean I'm blind to what is happening in the world of class D. I think I made that clear on my first post to this thread.

Though Genesis did use a class D amp, it was a far cry from where the technology has gone today.

Can you tell me what areas you think class D does not match your amp's performance?

I think the area where we can show up a class D amp is in the area of soundstage presentation, the ability to be fast and detailed, yet relaxed in the highs, and last but not least bass impact.

The latter seems to be one of the least understood, but most people also do not realize that a tube can be direct-coupled to a speaker. DC response in the output section, coupled with the ability to separate the driver and output section power supplies, means that the amplifier can operate at sub-audible frequencies without modulating its own power supplies, something that plagues many transistor designs.

The issue here is: design according to the rules that the human ear uses, i.e. create circuitry that allows for the least offense to those rules.

Audioperv, I'm not a nominalist, I am merely dealing with what is. As an example, I think we can all agree that our ears are the most important part of our listening, not our amps or speakers or taste of music. With no ears we would not buy audio products. So why in heaven's name ignore the rules that our ears use?? Yet many of the accepted design, test and measurement concepts do exactly that. Negative feedback is an example: yes, it lowers overall distortion, but- it *raises* the slight amounts of distortion that our ears actually care about. These are the high order odd harmonics- the 7th and 9th, which our ears use as loudness cues.

Take a look at the distortion makeup of the typical transistor amplifier and the class D amplifier and the issue becomes clear. Without question this is one of the areas that defines the leading edge in semiconductor amplifier design. This is where the Pass 1st watt amplifiers gain their traction and where low or zero feedback tube amps get it too. Clearly this area challenges class D designers as well. Like it or not Class A still defines state of the art. But again, like I said earlier, any designer who ignores the advances and significance of class D does so at their own peril.

Nelson lives just up the road for me. What I would give for a visit from him. Seriously, he would be shocked. That from a former Pass Labs fan.

When I first got into class D amps, I immediately saw more promise than drawbacks. My amp builder cut his audio teeth designing no feedback class A amps. There is no looking back for him or I.

My own system has been criticized over the last three years. I was told just the other day by a fellow audio enthusiast class D sound has an overemphasis of the leading edge, and a lack of depth. There was no question in his mind my system championed sound-stage presentation and detail.

Much to his surprise, on a visit just a few days ago, there is no hint of a hot leading edge. Depth leaps into the distance. Place of the music's origin superimposes my own walls.

Why the change? It is the learning curve I wrote about. The choice of caps, of speaker cables, and of source made all the difference.

Atmasphere, if only you could hear this.

Muralman1, here indeed is one the bigger issues of forum use in high end audio! We use a lot of the same language in description of system attributes, yet have no way of knowing if we actually mean the same thing with the same depth. So there is no way that I would know what you have, just as there is no way that you would know what I have without us hearing each other's setup.

The learning curve is without a doubt a serious concern. What I have seen of class D amps confirms your own findings- proper setup pays huge dividends (regardless of the technology). We deal with the same issues all the time with our amps too. I do wonder about some of the comments seen in the press that started this thread- how much was said based on setup issues?

I have to pay closer attention to Class D amps. I've read a lot about them but really considered them. I looked at the Nuforce speakers and Nuforce nine amps at ces. It sounded good but didnt move me. I just returned from RMAF and wow! What a show. Im considering the Acoustic Zen Adagios as my next speaker. I talked to Robert Lee of AZ and I told him the Halcro/AZ combo was awsome at the show. He said for the price range i want to be in, that i should consider a pair of moded belcanto 1000 or red dragon amps to go with those speakers. He said they sound as good and in some eyes better than the halcro/az combo. The same goes for the national sales rep for joseph. Im very familiar with joseph speakers. He mentioned that the Belcanto 1000 amps were mind blowing amps with the new RM 33s speakers. Now i want to hear them.