As I said the other day, “It is my estimation that the EL84 would greatly benefit from a lower percentage UL tap transformer.” Whereas there is much to be learned from the current data set taken with the Edcor GXSE10-5K transformer, I have decided that a different configuration needs to be tested as well.
After checking with a couple of different companies I decided to have Musical Power Supplies wind me a custom SE-UL transformer with a 20% UL tap. This transformer will likely not arrive until early June. At that point I can retake the data with the different tap position and see how the results differ.
In the meantime, I will continue to go over the first set of EL84 data to see what else I can glean from the numbers. There is at least one, and maybe two or three, operating points from the 40% tap data which I would recommend using. But I really want to be able to publish both sets of data together and compare and contrast operation.
As always, questions and comments are welcome.
Question:
The closer the screen tap gets to the plate, the more triode like the behavior becomes, and the closer the tap gets to B+, the more pentode like the behavior becomes? Seems logical to me. My personal experience with UL amps has been repairing push pull ones, and never really having to mess with the output transformer. (Good quality transformers of any type seem to have an “eternal life” if used within their ratings)
Thanks for the update. I am excited to see what you learn!