Nuvista Tubes - General

To clarify one other thing, Nuvistors are vacuum tubes.

Appreciate the clarification. Then, given they are vacuum tubes, assuming all else being equal, should one expect to achieve the same level of "famed" tube sound by using nuvistors (as compared to some other vacuum tube)? 

No. Not necessarily. It depends on everything - circuit, quality of transformers, type of tube, configuration of tube, quality of passive components. Adding tubes is not a panacea for some "tube sound."

Of course there are direct coupled tube amps. The Loftin-White instrumentation amps, designed in 1929, and still used today, were direct coupled designs. The Acrosound Stereo 20-20, designed by the brilliant Ed Laurent, only has an input coupling cap

" The Acrosound Stereo 20-20, designed by the brilliant Ed Laurent, only has an input coupling cap"

This technically should not then be called a direct coupled amp. As there is a cap in the signal path.
It should be described as a capacitor coupled amp with direct coupled output stage.

PS: But wait it’s not even that, it has an output transformer as well, so it has transformer coupled output as well. So in no way can this be called a direct coupled tube amp.

http://www.cma4ch.org/chemo/image/hifi/acrosound-stereo-20-mod-r.jpg

http://2.bp.blogspot.com/-AuRjf-5iXM8/UEYcDrM6X8I/AAAAAAAAAew/RixShlEJghU/s1600/Acrosound_20_20_sche...

Cheers George