Guy...... The EL34 is a pentode also, not a triode. So no triode mode. Dennis is currently a strong believer in designing single ended pentode amps that run Pentodes "the way they were designed to be run". I'm new to both tubes, so I don't have much preconception. I will go back to listen with the EL34 (and the KT150's) again, no doubt. The 6V6's just hit me hard the none of the other tubes did, so I'm drawn to listen to them for a while. But all this audio perception is very fluid. So I will likely contradict myself in short order! 
...........Peter
Hi Peter.
I have been in audio stuff, mainly tubes, for the past 45 years,
therefore I know quite well that an EL34 is not a triode
and that a EL84 is a pentode.
However, I can give you two examples of manufacturers who wire
pentode into triode.
Decware SE84C+ (EL84) and Wright Audio Lolita (EL34).
A pentode wired into a triode give surprising results.
I am not saying that pentode cannot sound as good as a triode,
but up to now,
I did not hear pentodes sounding as good as triode
or pentode wired as triode.
I have a Niteshade Audio NS10 with 6L6 wired as pentode
and it's far from sounding as good as my Decware EL84 SET.
That's my opinion based on my experience,
results and opinions can vary with different pair of ears.
Guy 13
The guy with 66 years old ears.
