Warren, the Penta/Shuguang KT88SC is as good an '88 as anyone has ever made, according to LOTS of folk, so now you've heard about an excellent current-production tube. Western Electric is currently manufacturing excellent 300Bs, KT88s, and others, but high quality is expensive--the 300B is $550 and the '88 is $350!!!!!!! http://www.westernelectric.com/pricing.asp
But things usually work the other way. After rejecting an entire production batch and being out of stock for a while, GrooveTube has those great-sounding 12AX7Ms again, but they're NOT great-sounding or well constructed this time. Read about it on the Tubes Asylum, http://www.audioasylum.com/audio/tubes/messages/188228.html .
Unclejeff is correct too. But there are other reasons, the principal one being costs. It costs a lot of money to, for instance, duplicate the esoteric material combinations and the excellent vacuum pumping used in decades past. Occasionally the Russians or Chinese get it right; the Serbians (Croations?) at Ei got it right for years, but they're now out of the tube business.
Oh well. My 'solution' is to use NP 845s because old ones are frightfully expensive, to keep all the great-sounding Ken-Rad 6SN7s I have, and to continue buying carefully the world's best-sounding 'N7, the Tung-Sol roundplate.
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