Is this just a case of liking something different?Bingo.
Csmithbarc (System | Threads | Answers)
Both have their strengths and weaknesses, and neither is perfect, which is why there is always a debate about which is best.
Well, Tvad is right as long as this is occurring inside one amp- like if you have a switch to go back and forth. But- if you compare real triodes to pentodes **wired** as triodes, you will hear a substantial difference.
Ultralinear is a way to approach triode linearity with a pentode, without loosing a lot of power. It is a compromise. So is wiring a pentode in triode mode. If you really want to hear what a *real* triode **actually** does, you will have to get a real triode amp to do that. The difference will not just be 'something different' (all other things being equal), it will be a real improvement.
I would agree with both Tvad and Atmasphere. I have the Dialogue Two, and have been having alot of fun exploring the difference between the two modes. The more I listen, the more things I personally prefer in the triode mode, especially vocals, chamber music, and small jazz combos. Even full orchestral and opera can sound better in the triode mode sometimes, though more often the ultra-linear is better for that. I have found that there aren't very many generalizations one can make, it depends greatly on each individual recording. I often find that older recordings that were recorded with tubes sound better in the triode mode, but not always. I love playing around with it, that's for sure. As Atmasphere comments, it has made me curious to explore a SET amp someday.
I'd just like to add that what you're doing by flipping the switch is only a very vague comparison of the general characteristics of a Triode-based amplifier, and an Ultralinear output circuit. What you're REALLY comparing is your Primaluna amplifier with the output tubes' screen grids connected in two different ways.
Changing this connection affects a bunch of circuit parameters simultaneously, including its static linearity, transconductance, plate resistance, grid-to-grid capacitance, output transformer HF damping, etc. etc. . . . all of which will interact with the manner in which the global negative feedback loop (if applicable) behaves. And since it's really impossible to get all of these parameters perfectly optimized for both modes, some of the differences you hear in the sound are going to be due to side-effects from switching between each mode, rather than necessarily from their generic differences.
So IMO you can freely decide which one you enjoy more, independently of any preconceived biases about Triode/Ultralinear circuits in general . . . and your experience with this switch on the Primaluna may or may not have any correlation with what you prefer on other amplifiers.