EL 34 vs. KT 88 ---- What's the difference?

Any further thoughts?

Why can some amps use EL34 or KT88 while other amps cannot use them interchangeably?

Does the output transformer have to "match" the tubes? If yes, what are the impedance differences?

Some amps can use both el34s and 88s b/c they have variable bias, allowing you to adjust the bias to the appropriate level for different tubes.

Stewie, I think it is not that simple. Different plate voltage and the bias range of the fixed bias circuit both come in to play I think. Just having the ability to adjust bias is not enuf. A user should always ask the manufacturer if use is possible, or at a minimum a knowledgable techie (which I am not) who knows the amp before trying different tube types.

Is there anyone who has an amp that is made to handle both EL34 and KT88 and prefers the EL34 generally, that is if you had to make a choice you would stick with EL34 over using the KT88. I think one of my amps (Music Reference RM9 SE) was built around the Siemens EL34 tube, but I still think it sounds better with the Genelex KT88 reissues.