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Can I use a Russian 6P15P-EV in place of a 6BQ5/EL84/6P14P-EV in my PP amp?

indeed, its been on extended loan for a long while now. I need to fiddle with the low distortion mode again. I had it working at one point, its something funny around one of the optocouplers. I replaced it and it was fine for a while but now it doesn't want to lock in again. Probably one of the many 50 year old components ailing. Luckily tube amps don't really need the ultra low distortion mode so I haven't bothered with it.

on to the 6P15P, I found this discussion on them and how to make them perform a bit better than simply wiring the suppressor to the cathode like normal. I'll try this next time I put in an order, i don't have the right zeners on hand.

Using 6P15P in triode at 300V - suggestions?

There's some confusion about the G2 rating of this 6P15P. Some data indicates 330V for both anode and G2, while other comments suggests the G2 is "fragile" and should be de-rated, maybe down to 160V like the EL83. So for those wanting to use this in triode e.g. in a PSE amp, how to proceed? A...
www.diyaudio.com www.diyaudio.com

basically if you run the suppressor about 30v above cathode voltage, it makes life on the screen easier and improves the performance as a pentode.
 
I've read that about the 6p15p and have been planning to do the experiment. I have a full case of the 15's so it's nice to have an idea about how to use them effectively. So far I've only used them as drivers for SE GU-50's so haven't really needed to adjust the suppressor.
 
I have 6P15P-EV running U-L at 310V and 40 mA idle per tube. Have not yet seen any issue. OPT are tapped at 28%( scavenged from a Sherwood S5000 ). I have some -DR suffixed 15's to try eventually. The amp is built on Pete Millett's ETF competition amp boards with fixed bias set with multi-turn pots...the finals are lined up to the fraction of a mA and they hold bias settings well. Sound good too... :) As mentioned before, there is a jumper between pin 3 and 6 to deal with the separate g3 connection the 6P15's have over EL84/6P14 basing.

On that separate g3, I plan to try elevating the g3 by 9V with a battery and see what happens. With pentodes in TV service this is generally done to reduce a particular type of distortion known as 'snivets'. It is usually higher voltage( 30V? ), and also tends to square up the gentle knee displayed by pentodes towards the sharper beam plate. With Tv tubes the usual construction IS beam plates so 'who the heck knows?'...LOL

It sure works pretty well with g3 tied to the cathode pin.

Douglas
 
spantou01 said:
Many of us have come to depend on Russian 6P14P-EV tubes for our Dynaco SCA35, Fisher SA-100 and other 6BQ5 based amplifiers, where the output tubes are running close to the voltage and dissipation limits. With the scarcity of 6P14P and its variants at the moment one wonders to what degree and under what operating conditions 6P15P-EV would work satisfactorily in an amp designed for 6BQ5 type tubes. I have a box of them and they seem to be considerably less expensive to buy, even now, than “real” 6P14P-EVs.

If you search the internet for an answer to the question in the thread heading you will find many warnings that 6P15P-EV is a fragile tube, but no direct answers. I have been trying to get at the bottom of the anecdotal: “they are more fragile than …”. I know what the spec sheet says, but the Russian specs are notoriously conservative.

Has anyone reading this actually tried 6P15P-EV in place of 6P14P-EV and experienced failures? Presumably screen failures. If so, was it in UL mode, pentode and at what screen voltage? I have scoured the internet and found many “they are more fragile” references, but have not found any evidence of someone who actually tried it and experienced failure in this swap. If you have experience with this we would love to hear about it. I do know of someone that used 6P15P-EV successfully in his Baby Huey build, but he had variable screen voltage and monitored screen current.

I wanted to determine this for myself, so I’m currently building a Tubelabs SPP (Simple Push-Pull) amp (http://tubelab.com/designs/tubelab-spp/) and adding fixed bias based on Dave Gillespies’ EFB design and variable screen voltage (in pentode mode). I plan to run the 6BQ5 power tubes at 320V (plate to cathode) and screen supply voltage variable between 200V and ~300V, and compare performance under these conditions with 6P15P-EV. I also will connect UL output transformers if the first experiments work well. I will report what I found. Unfortunately I do not have the capability to measure distortion.
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I've not found the to be scarce at all, but it's been 6 months since I've placed an order.
 
Thank you for you input. Indeed, if one is willing to pay enough for it nothing is scarce at all.

I wrote that in June 2022. The availability of 6P14P-ev changed drastically in the prior 6 months and the price trippled.

But the point of the thread was to explore the usability and limits of 6P15P-ev as a substitute for 6P14P-ev.
 
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