What do the different tube amp types mean?

Realdeal, there are no practical OTLs using 300bs, 211s or KT88s; just for the record.

Ralph,I think Realdeal is right,I also made an OTL using single KR52B,5R4GYB  tube rectified  with 600V on the plate.,no feedback and what a transparency.

@amfibius  Thank you so much for the nicely concise overview of how the tubes work.  This was simple, and to the point. I hadn't come across something like this until just now. :)

Realdeal, there are no practical OTLs using 300bs, 211s or KT88s; just for the record???

Am I reading this correctly??? If so I can tell you that Transcendent Sound has amazing OTL for sale.

http://www.transcendentsound.com/Products.html

http://www.transcendentsound.com/Masterpiece.html
http://www.transcendentsound.com/300B_OTL.html

notnow2,How did you know that is not practical?I also designed & build  one with interchangeable output tube using only one of either VV52B,,300B or KT88.With proper design,you can use any power tube to make an OTL.