Actually, I think the ET2.5 arm is a brilliant design. Being an engineer myself, I can understand the way he manipulated the design and the materials to give a very cost effective and highly functional design. Living with the arm for so many years gives one an appreciation of how well he did this. It's relatively easy to build cost is no object designs. We are surrounded by them in hi fi. The real trick is to design a great product that many can and will afford and that functions at the state of the art.
This is what Bruce did. In my view the main difference between the very expensive air bearing arms and the ET is the air pressure that is used, very expensive materials, and extensive machine work. The ET arm is made from plastic mouldings done to a very high level of precision. This kept the price down to an affordable level. The air pressure issue can be dealt with. The expensive materials and machine work are not needed. Yet, the performance is excellent. This is the mark of a great design. You should appreciate this and encourage this approach for the health of the industry. The problem is most engineers are not as good as Bruce.
I suspect the design is maxed out. It can't get any better without a completely new model for which there is no market. Doesn't sound like a good business proposition to me. It probably won't happen unless the vinyl resurgence is much bigger than I think it is.
Bruce stopped developing the ET arm when it was no longer cost effective to put development money into them. CD's are the cause. And actually he kept refining the design past this point but the fact is there were few customers. However, the arm is still available but the price is significantly higher than you remember. I think I paid $3000 for my new ET2.5 about two years ago.
Air bearing arms have always been exotic. They have always appealed to the more technically inclined person who understood the advantages and were willing to walk the extra mile to extract the best from them. I'm one of those. Anybody who settles for a pivoted arm is, in my view, willing to settle for less than the best. I think of them as lazy which is not a good attitude for creating the best system possible.
Damn, there I go again-being honest!! But so be it. I know I have just insulted nearly every member here (everyone with a pivoted arm, that is). I don't care. I'm not here to play politics.
Oh, and Myles, you never did answer my question about which compressor you were using. I would still appreciate an answer.