2. amps-preamps
  3. 164261-132585

Pentode Power Tubes - Ultralinear vs Triode

While I’ve seen a bunch of posts on power tube rolling, I haven’t seen much mention of how preferences correlate to what mode you run if your amp has that option. I have a Primaluna DPHP that has the Ultralinear/Triode mode remote and can run a bunch of EL34 variants up to KT150.
So far I’ve only tried the stock EL34 and Tung-Sol 7581A and seem to prefer Triode mode with both. Before coughing up for another set of 8 to try I’m doing more research. I think based on my preferences so far that the bigger, punchier tubes may not be the way for me to go. I could be destined to find my way into SET amps eventually.

So which tubes do you prefer in what mode of operation?
cat_doorman
atmasphere's avatar
atmasphere
11,574 posts
 
FWIW if ultra-linear is set up correctly, the result should be a pentode or tetrode power tube operating with the same linearity as a triode but with about 90% of the power it could make as a pentode or tetrode.
cat_doorman OP
236 posts
 
@atmasphere always nice to get answers from an expert. They never really covered vacuum tubes in the few EE courses required for an ME degree, and those are only a faint memory. From further reading I gathered that the ratio of the screen-grid and plate can vary quite a bit to find the sweet spot in ultralinear and would be dependent on the tube type. So with tube rolling on an amp like mine (Primaluna DPHP) would running in triode mode be more consistent when comparing different tube types?

What about tube life? Hypothetically, if you adjusted for the same output voltage, would one mode be significantly harder on the tube than the other?
rodman99999
5,981 posts
 
"FWIW if ultra-linear is set up correctly, the result should be a pentode or tetrode power tube operating with the same linearity as a triode but with about 90% of the power it could make as a pentode or tetrode."                                                                                                                                        Bless Blumlein, Hafler and Keroes's hearts!
atmasphere's avatar
atmasphere
11,574 posts
 
would running in triode mode be more consistent when comparing different tube types?

What about tube life? Hypothetically, if you adjusted for the same output voltage, would one mode be significantly harder on the tube than the other?
The patent suggests that the ratio is independent of the tube. Ultralinear has nothing to do with tube life either. Plate voltage will if the proper bias point for that plate voltage isn't observed.

 
Bless Blumlein, Hafler and Keroes's hearts!
And I guess Acro Sound too.

More to discover