Are most tube preamps ‘ultra linear’?


Is ultra linear prefered ?

hard to discern this designation when reviewing specs. 
emergingsoul
I read this thread because I am new to tubes.  Now I know a little about what ultra linear refers to.  The condescension in this forum is at times amazing.  Big fish in a shallow pond, I suppose.
One thing That is good to look for is a preamplifier operating in pure class A . I find their purity very appealing 
a  DHT is the purest single ended But it lets you hear everything 
not all speakers and amplifiers are a ideal match . I have owned 
several hand built models from Vacuum tube Guru Radu Tarta 
exceptional build and sound quality.
@audioman58 : All tube preamps operate in Class A! They have a single tube connected to the output straight - or through a cathode follower or a transformer! 
DHT triodes are almost never used as preamp tubes because the gain is way too low - plus noise is a problem! 
Hello Jason and others a DHT preamplifier,
is single ended and the purest type of Vacuum tube preamplifier 
it being Direct Heated Triode has a Sonic purity most people 
Have not had the opportunity to hear. I mentioned RaduTarta 
for he builds these one at a time and prices can vary greatly 
depending on parts quality and transformer and Chokes quality .
something worth investigating if you truly want something exceptional starting maybe around $4k ,