Hopefully I got it sorted out.
Several hours after what I thought were the correct tubes for the SE84UFO I checked the forum and darn (not those exact words but close).  The Russian designation of a SV83 is different.

OK I'm a little slow the 84 designation is in the name of the amp.
Doh!!!

I tried to cancel the order but no luck.  I requested an EL84 and I got pushback.  I sent pictures of the pinouts to show the SV83 vs the EL83 and still got pushback.  I finally found a non ebay store that contradicted what they were sayng all along.

The Reflector 6p15p-EB (SV83) is similar to EL84 Tube Types

Ebay
EL83 = SV83, 6P15P

This was my final response

Of course such tube is closer to el84, but with other pinouts! You need some adapter or make the changes in your scheme!
SO finally i will send two tubes 6p14p/el84 to you, maybe matched pair) - it will be my present for you!:)

Are there power tubes on ebay that I can try or do I need to stay with American venders?

Cheers

LT;DR EL83s are NOT compatible with the UFO amps, but they are adaptable.


Here's the deal. A year or so ago when I ordered my UFOs I was intrigued by the possibility of using EL83s, but there were stories on this site about bad things happening if you tried them. So I checked the datasheet and sure enough EL83s have a different pinout than 6P15P types  and EL84s. Note also that "SV83" is brand name for 6P15P type tubes. I don't know exactly how EL83 got in the mix, but I suspect someone saw SV83 and figured EL83 would be the same thing. They are similar, but they most definitely are not interchangeable. But they are adaptable.

If you don't want to buy tubes from Steve there are plenty of people selling 6P15P, 6P15P-EB and 6P15P-EP tubes that you can use, and they are generally cheap. I bought a number of them, some sound very good, others less so. But for me none of them sound as good as adapteed EL83s. If you are interested in my EL83 journey it is here:

https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1607194889

I don't know that being an audiophile physicist is a good reason to trust me, but I do tend to gravitate to the road less traveled. So, yes, I've pretty much stayed with EL83s since December. I started with Tesla, and tried Siemens and Telefunken and like TFK the best (they are also the most expensive, go figure). I continue to wonder if I like the EL83s just because they were such a hassle to get them to work, so I'll swap in 6P15P types (both Decware that came with my amp, and Ebay) occasionally and I'll be damned if I don't keep coming back to the EL83s. Actually just did it this morning, before I saw this thread.

Of course the input and rectifier tubes matter as well. I've been using Amperex 7308s (bought them in the early days of the internet for a few bucks each) and Mullard Fat Base Smooth Plate GZ34s, which were a struggle for my Scottish Heritage, but worth the investment.

So, if you decide to pursue the EL83 option let me know how it goes, I'd be very curious what your experience is like.

Here's the link for the tubes:

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

As for the EL83s, I just took them out this morning to test them (and try some 6P15P-EPs, which were good, but not as good as the EL83s) and they test the same after 500ish hours as when they were new, so I'm pretty optimistic about tube life.

I have bought many such tubes from Russia via several merchants. BUT. . . I have never bought a pair that sounds better or lasts longer than a pair that Steve selects and puts through his testing. So though I have about 20 pairs of spares. . . once a year or so I buy a pair from Steve for my Monoblocks and my Taboo amp. They just sound the best and don't fail.

I haven't had the same experience with ER versions so I keep using tubes from Steve.

No. 6P15P are the tubes used in the UFO amps. That is the real tube designation, they are mislabeled as EL83. 6P14P are EL84 equivalent and will work in UFO amps without an adapter, but not as well.

 

Well my near tube ebay disaster worked out.  I originally ordered EL 83 that were supposedly SV83 but thanks to everyone I caught it before they were shipped.  They wouldn't let me cancel the order even though I provided pin out pictures and other sites showing they wouldn't work.
What they did allow me to do was substitute 6P14P an EL84 equivalent.  I just put them in and to me they sound really good.  They were used tubes but I feel that they are much more open and more high frequency emphasis than the tubes included with the amp.
I changed out the input tube to a 6922 and I just as happy as a clam.

You are using the incorrect tube. You should be using the 6P15P-EV tube.

Lon, are you using the ebay EL83 -> EL84 adapters? I've been curious how they work in the Decware amps.

I have about fifty hours on the Mullards now and they are sounding quite nice. A warmer, bolder presentation than Steve's which are faster and more focused.

It's nice to have options!

I mistakenly purchased these instead of the 6P15-EV (6P14P / EL84 / 6BQ5 and 6P14-ev "Reflector" EL84M el84 7189 6BQ5) a while back.  Are these the adapters that would allow me to use these on the ZenUFO25th?
https://www.ebay.com/itm/303631540159
I appreciate the advice.  Thanks.
Bob

If you bought these: (6P14P / EL84 / 6BQ5 and 6P14-ev "Reflector" EL84M el84 7189 6BQ5) then you do not need an adapter. EL84s work fine. It is EL83s, sometimes advertised as SV83s that need an adapter.

It is confusing. This is the situation as clearly as I can state it:

The tube that Decware sells is the Russian 6P15P-EV. There is also a -ER version and the just plain 6P15P. There is no western tube equivalent for the 6P15P type. FYI/FWIW the -EV and -ER suffixes designate higher spec, more durable tubes. But electrically they are (essentially) the same.

The UFO amps are also fully compatible with the EL84 tube. There is a Russian version of the EL84, the 6P14P that also comes in various versions. There are many European and American versions of the EL84. The American designation is 6BQ5.

So far so good. Then there is the SV83. This a brand name owned by an American company and is used for 6P15P type tubes. AFAIK they can label any 6P15P type a SV83. Since an SV83 is a 6P15P it is fully compatible with the UFO amps, but you don't really know what kind of 6P15P you are getting.

Finally there is the EL83. It is similar electrically to the 6P15P and EL84/6P14P but has a different pinout so it isn't directly compatible with the UFO amps (but it is adaptable). Presumably because "EL83" looks a lot like "SV83"  the 6P15P/SV83 tubes are also advertised as EL83, but this is 100% wrong. There is no Russian EL83 (that I know of). If it is a Russian tube it is 6P15P/SV83 or perhaps is 6P14P/EL84. There are European made (and perhaps American made or at least relabled) EL83s, that may be advertised as SV83 but this is also 100% wrong. There is no Western SV83/6P15P. The American designation for an EL83 is 6CK6.


I hope this helps, but in rereading it seems like maybe I just made things worse....

Thanks CAJames. UDAMAN!

Where I got tripped up was
EL803s TESLA EXPERIMENTAL PROTOTYPE Serie Early 50s MATCHED PAIR Tubes = EL83

Ebay listed this tube as a SV83 6p15p which apparently it isn't. I was able to switch to the 6p14p/EL84 which for me worked out really well thanks to the posters here.

Much apprieciation

First let me say I couldn't be happier.  I just purchased quan10 6p15p advertised as slightly used for $20 with shipping.  

My thoughts if half of them are good I'm ahead and it will probably take a long time to find out.  I put in the first pair and all I can say is what a great amp.  It still sounds really good.  I'm not good enough to determine if it sounds better or even different from the 6p14p /EL84 that I was really happy with so I figure I'm set on output tubes as I still haven't even broken in the originals.

I just purchased  quan 2 5z3 for $16 and a 4 to 8 pin adapter so I'll be able to swap out the rectifier soon to see if it changes the sound.  They were tested and showed numbers above what they said was minimum and appear to be stronger than the 80 globes that were a lot more money.  One was a Sheldon and the other was a National Union so I don't know how to check but I would bet they're over 50 years old and probably even older.

Again thank you to all the pioneers who were willing to share knowledge allow me to make significant changes to my amp for less than lunch for two at Mickey Dee's.

Quote:


Why do you say that?

The way I read Steve's paper on the Hazen grid mod:

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

Is the thing that matters is whether the suppressor grid is internally connected to the cathode. This is indeed the case for the EL84, but not for the EL83 and (properly adapted) the Hazen grid mod should in fact apply to the EL83. That is one of the things that attracted me to this adventure.

Of course the question is properly adapted. The gory details are the EL83 and 6P15P have the suppressor grid on pin 6 and cathode on pin 3. The EL84 has both the cathode and suppressor grid on pin 3 (i.e. internally connected) and no connection on pin 6. So, if the adapters connect pin 3 to pin 6 then you are correct, and no Hazen grid mod. However, the ebay adapters I over a year ago did not do that, but I didn't like them for other reasons so I had custom adapters made. Those were different (at least cosmetically) from the ones that are on sale now, but the bottom line is if you have a multimeter, and you care, you can test to see if there is connection from pin 6 on top to pin 3 on the bottom. No connection, yes Hazen grid mod. Connection, no Hazen grid mod.

If the ebay adapters negate the Hazen grid mod that would certainly reduce the appeal of EL83s.