Tube Single Ended Triode Questions??


Why can't SETs be built with more power and able to drive a bigger range of speakers? I know the 300B tube can goto 10 Watts or so, and the 2A3 in only 2W, but why can't they do an amp that is like "single ended parallel" with several amp stages in parallel? Or, why can't tubes be used like EL34, 6550 and KT88s (I guess these are known as power tetrodes) and make higher power SE amps? I guess the idea behind SETs is to avoid splitting the siginal into push-pull and they are class A, but you give up a little S/N ratio with a SE circuit - is this correct? Are some tubes too noisy to run single ended, or can only a portion of a KT88 be used in SE mode?

Also, the output transformers- is this really what seperates okay from great SETs? Are quality transformers what makes them so expensive for what appears to be a very small parts count?

I have some question for latter about SE -vs- Balanced preamps too - is it a simialar trade off to SE/BAL amps, but I will save that for latter.
6550c

Showing 2 responses by victor_hrynchuk

I like how vendors rate the power output of their amps. 50 wpc from two parallel 6C33C. To put it mildly just a little bit of overestimation. Claims of 50 or 70 Wats of output power from a single 845 or 211 tube are just plain bogus.
One 6c33c in class A will provide you with something around 18 Watts. Two tubes theoretically will provide twofold increase, but only theoretically. To do this they must be supper precisely matched and for 6C33C it is practically impossible, so on peaks one tube with bigger current will swamp another. I believe you can get 30 Watts for from parallel 6c33c SET amp. The only way to get 3db increase of power from paralleling two tubes is to use two independent power supply , two output transformers and parallel the secondaries of the output transformers. The solution is very expensive.