What do the different tube amp types mean?

@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.

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

Correct; for example at one of the links above, there is a 300b-based OTL. It uses 4 power tubes per channel and makes 6 watts per channel (for comparison an SET using one 300b will make about 7 watts). We built a 300b OTL about 20 years ago and got a similar amount of power. If you have an idea of what 300bs cost, and compare that with the cost of the same number of 6AS7Gs (which can make 20 watts into 8 ohms), you see how this is a pretty good example of the word 'impractical'. 

You run into similar issues with the 211, KT88 and for that matter most of the power tubes commonly in use today. If you want to make a practical OTL amplifier, the three tube types most suited (due to availability and efficiency) are the 6AS7G/6H13C, 6C33 and the PL519.

Ralph,The OTL is only using one DHT tube and 2 other tubes,3 tubes total per ch.,Audiophiles are looking for the best sound, just like the Atmas,that you claimed they are the best for the money.Are we  looking practicality or sound quality?