After some proper time tracing the curves, here are a set of Russian high-frequency pentodes in triode-mode for comparison. I was looking at closer ones to D3a and these are the ones I had at hand and wanted to include in the tests:
Well, as you can see in the table above, the 6e5p and 6e6p-e (both tetrodes) were included in the list. Some interesting points to highlight:
- 6Z51P is the closest to D3a in terms of mu, however it’s slightly higher.
- In terms of transconductance, 6Z9P, 6Z11P, 6E5P are closely to D3a
- In terms of anode resistance:
- 6Z9P and 6Z11P have lower Ra as well as 6P15P, 6E5P and 6E6P-E
- 6Z49P-D is the closest
- Overall, 6Z11P is very close but with lower Ra and mu, but the closest is 6Z51P which has lower transconductance, lower power dissipation, slightly higher mu and Ra.
Haven’t tried 6Z52P as don’t have any.
Given the rocketing prices of the D3a and E810Fs, 6Z51P seems like a good alternative…