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Audio Forums >> Frequently Asked Questions >> Why the 6P15P-EV over the 6P14P-EV
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Message started by oztayls on 03/13/21 at 22:21:57

Title: Why the 6P15P-EV over the 6P14P-EV
Post by oztayls on 03/13/21 at 22:21:57

In the user manual for the SE84ZS, Steve mentions the choice made for the Svetlana 6P15P-EV in favour of the EL84. Given that the direct replacement for the EL84 is the 6P14p, why did he choose the 6P15P-EV, which is not a direct replacement? I haven't been able to find any info about this. Thanks.

Title: Re: Why the 6P15P-EV over the 6P14P-EV
Post by Lon on 03/13/21 at 23:07:33

I think the answer can be found in this paper:

https://www.decware.com/newsite/paper145.htm

"There are two unique pentodes that can be found in many Decware amplifiers. These are the Russian 6P15P-EV and the EL34. What makes these pentodes different from other tubes is that the suppressor grid is not internally connected to the cathode. These two tubes can be wired as either pentodes or triodes."

I think he chose the SV83 for models Rev. A and further (the initial choice was the Svetlana version of the 6P15-EV, then when Svetlana devolved to not always being the "EV" version he moved on to verified 6P15-EV) as it can wired as a triode in a manner I don't think the EL84 can.

Title: Re: Why the 6P15P-EV over the 6P14P-EV
Post by oztayls on 03/14/21 at 00:31:37

Well, that is perfect! Thanks so much Lon, and as you said, explains it all. Now, I also have a cheap little EL 34 desktop SET (Boyuu A2) that sounds really good for the price of it. It would be worth a shot doing the "CCE" mod to that and running the 6P15P-EVs just to see what is possible! I'm not sure whether it could be done on the A2, as I haven't yet opened it up, but it sounds like it could be a bit of a fun experiment.

Title: Re: Why the 6P15P-EV over the 6P14P-EV
Post by Crazy Bill the Eel Killer on 03/17/21 at 19:39:51

Actually its the screen grid that get's strapped to the plate to make a pentode behave like a triode. not the suppressor grid. A strapped El84 ( or 6P14P-EV ) makes a triode just like a strapped 6P15P-EV.

Steve chose the 6P15P-EV because it is a video tube, not an audio tube like the EL84, resulting in extended bandwidth and speed. Most of us who have compared the two I think would agree.

The suppressor grid comes into play when the CCE ( Christmas Comes Early ) mod is applied. In the 6P15P-EV the suppressor grid is separately accessible which allows the mod to be applied. In the EL84 the suppressor grid is internally strapped to the cathode, meaning the CCE mod has no effect when using the EL84.

Most of us far prefer the CCE mod with the 6P15P-EV.

Cheers, Crazy Bill