Perhaps someone who purports to know the difference could enlighten me,
as I
really am interested in knowing. (Arfa)

Hi there - I use valves on a daily basis, but I don't know the
construction details. As they say, "I know a man who does" but he's in
France working on Italian sports cars! There are some books on this,
though I don't have the references. When the weather cooled down last
night I did try and google a bit, since I'm curious myself. The sites I
came across tended, again, to be enthusiastic DHT users/designers. You
will find masses of references to DHTs in any search on:
www.audioasylum.com
www.diyaudio.com
These two sites are about the best for design details and user
experiences. Particular sites referring to designing with DHTs include:
http://www.nutshellhifi.com/triode1.html - Lynn Olsen's many DHT
designs
http://members.aol.com/sbench101/ - Steve Bench's designs
http://www.vt52.com/diy/philosophy/philosophy.htm - Jim de Kort's
designs
http://www.audiodesignguide.com/se/katelelo.html - an example of DHT
small tubes
http://www.6moons.com/audioreviews/steve/steve.html - a little history
of the re-introduction of the DHT into current design
http://www.positive-feedback.com/Issue16/kennedy.htm - Preamp design
with DHT small tubes and reference to filament supplies (this is a
whole subject on its own, and filament supplies do sound different in
experiments we've carried out)

I don't know if any of the above will exactly answer your question, but
it should provide some knowledge of the current DHT design scene. Andy