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…
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.
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
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
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
Most likely, this information is not true.
For the CVC it shot my colleagues 6P15P mu in triode mode no more than 25.
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
Fixed, it was actually 22 :). I wrote the incorrect the grid step setting down
Tnx Ale
Ale, this great work! very valuable analysis!
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.
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
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!
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
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.
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!
My apologies, I just realized 6j11p is nearer to 6j9/6688/e180f. I also see the correction you made to Mu in the comments above.
Where I can download teh spice models ?
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
have you meassured the Rp (Ri) of them?
Have you read this post in detail?
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 !
Try asking in DIYaudio forum. I’m not an EL84 user and I can’t see the reason of moving away from the 6e6p-dr!
Ale
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
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.
Hi Joao. Agree, I’ve noticed this as well. Thanks for sharing your experience! Either way, for their price, the Russian valves are very good value for money!
Hi Ale–
Thanks for the blog and your DIY components.
I’d like to comment on the 6Z51P.
I have a recently constructed 45 amplifier using your gyrators on the input section.
I compared 6Z51P with E180F using cathode resistors and LEDs. Over several listening sessions, with multiple listeners, the E180F was unanimously selected as sounding the best, but no one thought that the 6Z51P sounded bad. In all honesty, it was not necessarily a direct comparison between them, as the gain of the 6Z51P is simply too high in my system (driven by 2V RMS DAC signal) and much more attenuation was required for the Russian tube. Overall, listeners thought it sounded a bit warmer than the E180F.
Prior to trying the E180F, I was completely satisfied with the sound and had no complaints. But the E180F brings a bit more detail and clarity without sacrificing anything.
The 6Z51P should absolutely be considered by anyone who is using a 9-pin tube socket which is wired for D3A and so forth–I have no doubt that, in someone’s system, it would sound really great.
We ran the 6Z51P around ~3V on the cathode and anywhere from 200 to 250V on the anode.
This is not exactly a relevant comment for this thread, but for completion’s sake, I also tried the 6N6P. This was a more rushed listening test and I am not able to come to a very strong conclusion (this requires a differently wired socket and I just don’t have the time to compare in the near future). That said, I think it is a contender as a great sounding tube just like the others mentioned here.
Unfortunately I do not have the ability to measure distortion or provide FFT graphs.
All of the tubes I’ve tried with the gyrator sound great. Of course, your experience may vary.
Thanks again Ale,
Kyle
Hi Kyle
Thank you for sharing your experience and feedback. Indeed 6Z51P is a valve to use. So it is the 6Z49P-DR, 6Z52P and few others, which sometimes are overlooked and replaced by a double stage of 6SN7!
Of course it depends on multiple things beyond the operating point and end-to-end system, in particular which output stage is driving. As you say, having too much gain may give also the wrong perception of its performance and sound.
Personally (and this is literally personally), I’ve been inclined to use the 6Z49P-DR (gold pins) and 6Z52P. The latter is a bit all over the place in terms of specs (and I have hundreds of them) so you need to submit them to the mercy of a curve tracer to get the best set or pair to use. If you live in the US, go for the 12HL7, a real sleeper and amazing valve. Mostly all of the ones I cite below, are of gain above 30, so would work well to drive a 300B, 45 or 2A3 depending on your source.
Let’s not forget the Post Office German ones C3g/C3m….
Needless to say, there are out there amazing drivers for a budget! no need to spend stupid money (without looking to undermine the amazing performance of a D3a or a E810F) but we all know where the prices have gone for some valves.
Here are some links of interest:
Hope you find it useful.
Again, glad you like the gyrator driver stage 🙂
Cheers
Ale
another amp. with these tubes
http://www.audiodesignguide.com/Ibridone/index7.html
If you can make the filament voltage work the PL802 is the real sleeper also and cheap.
I just want to extend my deepest appreciation to Ale for his work on this analysis. This has led me to design/build my great new phono preamp circuit using a two stage triode strapped 6Z51P. These tubes are a great find 🙂 direct phono capture here: https://www.youtube.com/watch?v=dBi1dVSF5vo