Dan,
IMHO the issue you are facing is fundamental one in that you are hearing the difference in amplifier topology - the EL34 amp is a push-pull probably configured as a pentode amp while the 300B is a single-ended (as you wrote) amp. The EL34 is a pentode tube but it can be configured as a pentode or as a triode. The pentode configuration gives more output power but at higher distortion. The triode configuration gives lower power but with lower distortion. I used to own a Cary/AES Sixpac that used EL34 in triode configuration & the sonics were really very good. (Too bad for me that I bought a 1-ohm version Apogee Scintilla that the Sixpac just could not drive!).
The push-pull amp will have more distortion (pentode config) & maybe even cross-over distortion since one/one set of tubes will be used to push & the other/other set will be used to pull. The matching of the push-pull pair is critical & it will never be perfect.
The SET amp uses just 1 300B tube to push & pull. so, by design the push pull ckts are perfectly matched - it's the same tube doing both! The distortion is (way) less.
Plus, reading other tube users' comments, it seems that the 300B has some sonic attributes that the EL34 simply does not have.
IMHO, Jjrenman was on the right path when he changed his pentode amp to a triode configuration (it is also why I chose the Sixpac as I, too, want a the pentode EL34 configured as a triode).
BTW, the 300B is a triode tube (& it sounds awesome) - there's a correlation here......
IMHO the issue you are facing is fundamental one in that you are hearing the difference in amplifier topology - the EL34 amp is a push-pull probably configured as a pentode amp while the 300B is a single-ended (as you wrote) amp. The EL34 is a pentode tube but it can be configured as a pentode or as a triode. The pentode configuration gives more output power but at higher distortion. The triode configuration gives lower power but with lower distortion. I used to own a Cary/AES Sixpac that used EL34 in triode configuration & the sonics were really very good. (Too bad for me that I bought a 1-ohm version Apogee Scintilla that the Sixpac just could not drive!).
The push-pull amp will have more distortion (pentode config) & maybe even cross-over distortion since one/one set of tubes will be used to push & the other/other set will be used to pull. The matching of the push-pull pair is critical & it will never be perfect.
The SET amp uses just 1 300B tube to push & pull. so, by design the push pull ckts are perfectly matched - it's the same tube doing both! The distortion is (way) less.
Plus, reading other tube users' comments, it seems that the 300B has some sonic attributes that the EL34 simply does not have.
IMHO, Jjrenman was on the right path when he changed his pentode amp to a triode configuration (it is also why I chose the Sixpac as I, too, want a the pentode EL34 configured as a triode).
BTW, the 300B is a triode tube (& it sounds awesome) - there's a correlation here......