Russian pentodes in triode mode

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:

6Z5P 6Z9P 6Z11P 6Z49P-D 6Z51P 6P15P 6E5P 6E6P-E D3a
Vf [V] 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3
If [ma] 450 300 440 300 300 760 600 610 315
Pa [W] 4 3.75 6 3.4 3.5 13.5 10.6 8.8 4.5
Gm [ma/V] 7 35 33 17.75 29 16 32 25 34
μ 44 36 40 44.3 79.5 22 30 34 68
Ra [Ω] 6K2 1k 1K2 2K5 2K7 1K6 960 1K3 2K
Ia [ma] 16 29 40 15.7 23 52 50 30 22
Va [V] 252 125 150 200 150 250 200 200 200

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…

6Z5P triode-mode
6Z5P triode-mode


 

6Z5P triode-mode SPICE model
6Z5P triode-mode SPICE model

6Z5P triode loadline 200K

6Z9P triode-mode
6Z9P triode-mode

 

6Z9P triode-mode SPICE model
6Z9P triode-mode SPICE model

 

6Z11P-E triode-mode
6Z11P-E triode-mode

 

6Z11P-E triode-mode SPICE model
6Z11P-E triode-mode SPICE model

 

6Z11P-E Loadline 220K

6Z51P triode-mode
6Z51P triode-mode

 

6Z51P triode loadline 220K

6Z49P-D triode-mode
6Z49P-D triode-mode

 

6Z49P-D triode-mode SPICE model
6Z49P-D triode-mode SPICE model

 

6Z49P-D
6Z49P-D

 

6P15P triode-mode SPICE model
6P15P triode-mode SPICE model
6P15P triode-mode
6P15P triode-mode

25 Replies to “Russian pentodes in triode mode”

  1. Great work!
    My experiments in this area showed there are some cheap tubes that can rival the d3a, but that the quality controle can be hit and miss so its worth taking advantage of there low cost to buy lots and select. Lowest thd tube @67vrms I found was 6j9p but only when run over its anode diss limit, 6e5p wasnt far behind. 6j52 gave ok figures, not quite up to d3a. Have some 6j11 to test. 6j9p gave less than 0.05% with harmonics only up to 4th I think.

    1. Hi Lorenzo,
      Actually 6j5, 6j9 and 6j49 look very good from a model perspective. Would be great to measure their performance.
      If you want, I can add a table with a summary of your THD measurements? That would be great to share as you have done great work on this space…
      Thanks
      Ale

  2. Thanks Ale.

    6P15P in triode mode with MU = 40 is really very new information for me.
    Ale, I do not doubt in your ability, but can you check this once more, please.

    Thanks,
    Rajko

    1. Yes, it looked high to me too, perhaps I wrote down the wrong scales when plotting the curves. Need to retake or double check…
      Ale

      1. Yes, I remember the triode curves I had at hand and the MU is about 25-30. I probably wrote down the wrong grid voltage steps hence misreading the actual MU. Anode current is likely to be ok, but the grid is not.

        I will have to retake this, apologies. Thanks for spotting it out!

        Ale

  3. This is great Ale. Russian pentodes are becoming more and more popular in pro audio too, and there is always the need for cheap alternatives. I have a batch of 6J51P, havn’t got round to using them yet but you might like to try them out – they were about £1.60 each.

    1. Hey Charlie, you are right but variance of parameter is significant so as recommended by Lorenzo above is good to have a good stash. 6j51 have about 10 so am fine, thanks. Would be keen to try 6j52 though
      Won’t see you this Thursday at the pub meeting as will be in Frankfurt, but hopefully we meet next time?
      Cheers
      Ale

      1. So from your suggestions, you think 6Z51P is one good alternative to the D3a? I can not justify buying any D3a to try out!

        Shame you can’t make the pub, but hopefully the new venue will attract a bigger turn out!

        1. Can’t comment on the sound of it as haven’t tried it yet.
          Yes, I will be in Frankfurt this week so can’t make it. We should try to meet up soon
          Ale

  4. I have tried some of these russian tubes, triode connected, in my headphone test and evaluation platform and in my GM-70 SE.
    6J52P: unfortunately it doesn’t sound good to me and to a musician friend. They are very harsh and bright sounding.
    6J9P and 6J11P are OK, but the european E180F and E186F sound better.
    The 6P15P-EV is not bad! But again, I have european equivalents that sound better.

    Sad but true.

  5. This is wonderful work and I am grateful for the fact that these results are being shared this way: thanks for that. I have question about the 6J11p. The 6j11p is the Russian equivalent of the American 6ej7/European ef184. Do valves of this designation really give 50mA/V, or is this a typo (like maybe the Russian 6j52p)?
    I have enjoyed this site very much. The work here is Very well done and nicely presented!

    1. Ciao Andrea,
      All model parameters are on the screen shoots above. I haven’t generated the spice models for all but you can do it yourself by editing any other one and updating MU, KG1, KVB, VCT, etc.
      Hope this helps
      Cheers,
      Ale

  6. Hi Guys , i am not technical person 🙂 i own pre tube use 6E6P-DR, may I change it to EL84 , do i need do any thing more inside the preamplifier ? and EL84 do better sounds ? Thanks in advance for your advice !

  7. Hello 6zh52p good bulb and it is important them correctly to make and accompanying parts large spread in the parameters
    each has its own ears

    of the best examples of 6zh11p –
    6zh11p Friazino gold numbered grid lamps
    6zh9p —
    1520 military execution
    6zh9p Friazino gold grid
    6zh9p-e Friazino gold grid 10000 hours

  8. these triode straped pentodes (and tetrode) work quite well. I tried most of them with CCS and I get distortions lower than 0,3% (330V rail and 100Ohm whit cap cathode). But they are quite picky about plate current. F.I. in a 6Z11P if you go from 20 to 30mA you can see 3rd and 5th harmonics disapear, leaving almost only 2nd. The 6E6 likes more about 24-26mA and D3A is the most “imune” to current, but “prefers” 20mA. This is and “average” statement as is varies a bit with the specimen. This change in distortion spectrum can make a signiificant impact on listening. Please bear this in mind when evaluating the tubes.

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