There is some value in the two critques that have been made of my post. However, I think there also some problems.

Dudley did not just review the DNM components. He devoted an entire Listening column to the history and ideas of the DNM designer, Denis Morecroft (April 2004). He devoted another Listening column to reviewing two DNM amplifiers and some DNM interconnect (May 2004). And then he did a follow-up review on the amplifiers in the May 2005 issue. I do not recall him giving this sort of attention to any other company's products.

Jan Vigne said he or she could not remember Dudley stating a personal preference for a particular case material. However, in my original post I quote Dudley saying, "I don't doubt for a second that the DNM preamp's low mass has something to do with how good it sounded." In the April 2004 issue Dudley wrote about the DNM amp cases, "those plastic boxes may lack grunt appeal, but their value in the war against distortion is obvious."

Given all the attention he gave to Morecroft's ideas and products and given his endorsement of the ideas concerning casework in the 2004 and 2005 quotes above, I think Dudley ought to have done one or both of two things in his recent review of steel cased and inner steel walled amplifiers. One, he could have explained why his thinking about cases has changed. And/or two, he could have asked the amp designers why they prefer steel cases and reported the answer.

This is not just a case of a reviewer liking the sound of, for example, both transistor and tube amps. I have nothing against that. Transistors and tubes are two routes to good sound but they are not really opposites. However, I think that plastic and steel cases really are opposites, in some ways. If the steel approach is right than Morecroft is wrong, at least with regards to the arguments he made for his cases. I think Dudley should give some indication as to where he stands.

In the August 2004 issue Michael Fremer reviewed the tangential tracking Kuzma Air Line tonearm. In this review he wrote, "When you hear a true linear tracker for the first time, you'll know it -- the absence of the etchy, pinched character present in all pivoted arms is among the most obvious differences.... When all playback conditions are ideal, the Kuzma Air Line is one of top two tonearms I've ever heard." From the rest of the review it seems that Fremer thought the Rockport System III Series 6000 tangential tonearm was the other top tonearm.
In an April 2007 review of the revised Air Line and the Kuzma Stabi XL turntable, Fremer wrote, "While it's true that a genuine tangential arm ... will eliminate the distortion products produced by the arc described by a pivoted arm's travel across a record's surface, experience tells me that distortions elsewhere in the reproducing chain are greater than those produced by the playback stylus's lack of tangency to the groove throughout most of its travel in a pivoted arm, and that tangential trackers are not worth the hassle and expense. Of course, that's my opinion; you may conclude otherwise. In fact, my position on this matter in 2007 is diametrically opposed to what I expressed in my review of the Air Line in 2004. Based on recent experiences with better pivoted arms, I've changed my mind. Perhaps another product will send me back again as I meander my own way across the record..."
Fremer acknowledged and explained his change of position. If Dudley has changed his position he has done neither. If he has not changed his position he should have at least asked the two designers of the steel body amps as to why they used steel and reported the response back to us.
DUP's comment that Dudley did not ask Moorecraft why he used plastic cases is wrong. Dudley reported Moorecraft's exlanation in his April 2004 Listening column. What he apparently did not do was ask the designers of the Audio Valve or the Shindo amps to justify their material.

I have no personal, professional or financial connections to the amplifier industry. I do not own DNM, Audio Valve or Shindo amplifiers (I own a Creek). Nor do I have any connection to Art Dudley other than I read his work in Stereophile. So I have no conflict of interest in making these posts. Other than saying that, I do not see why I have to explain to you, Jan Vigne, why I am making these posts. Other posters to the Stereophile Forum do not necessarily explain why they make their posts.
Sure I have changed my mind about various things in the past. So what?
If I were in Art Dudley's shoes I would have handled the recent reviews of the Shindo and Audio Valve gear as I am suggesting he should have.
I think part of the problem of some of the posters to this thread is that either they have never read Dudley's pieces on DNM in 2004 or 2005 or they do not remember the pieces. If they had, I think they would be more amenable to my opinion. Both the Listening columns are on this Web site. I do not think the follow-up in 2005 is on the Web site.