Just an extended FYI here, because some readings in forums and in tube stores induced a lot of head shaking reactions for me about these:

EL84/6BQ5/6P14 (type 1) vs 6P15/SV83 (type 2) vs EL83 (type 3)

AND NO, the 6P1 is not an EL84 type at all, with completely different pinout, and it has been mentioned that it is more like a 9-pin mini version of 6V6, similar to 6AQ5/EL90 (but those are 7-pin).

A lot of sellers especially mix up EL83 and SV83/6P15 all the time, which are completely different beasties!

There are three tube types, that often get confused, with potentially catastrophic results!
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The three types are as follows:
* 1) EL84 also known as (aka) 6BQ5 aka 6P14 - currently produced by several Russian, Chinese, Czech and Slovak makers
* 2) 6P15 aka Svetlana83 (SV83) - currently produced by several Russian, Chinese, Czech and Slovak makers
* 3) EL83 aka 6CK6 (Philips, Mazda, Tesla, La Radiotechnique, NOT made anymore)
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NOTE that the SV83 is NOT an EL83, these are totally different beasts!
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Type 1 and 2 are compatible, IF you have a hefty (>1K) screengrid resistor, have an already adapted Decware SV83 amp, or modify your tube socket with a switch, jumper, a tube adapter, or the Hazen mod (0.1uF/400V cap between pin 3 on one cap lead and 1 or 6 on the other), but type 3 is NOT at all compatible with 1 and 2.
EL83 requires rewiring, different bias, and potentially modified power supply setup!
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Here is why:
* 1 and 2, so EL84 and 6P15 anodes/plates are rated at 12 Watts.
* There are 3 grids in pentodes, one of which is the suppressor grid.
* In the EL84 types, the suppressor is tied to the cathode, so not even on a separate pin to the outside world of the tube.
* In the 6P15/SV83 types, the suppressor is not connected to anything inside of the tube, but tied to pin 1 and pin 6.
* In both the EL84 and 6P15/SV83, the screen grid (aka grid 2) is connected to pin 9 (keep that in mind)
* The actual EL83 (aka 6CK6) is NOT an EL84, and do NOT confuse it with an SV83, because its plate (or anode) is rated at 9-Watts with lower ratings overall, AND the suppressor is tied to pin 6 only, AND the screen grid is tied to pin 1, with pin 9 empty!
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So, what happens, if you plug an SV83/6P15 into an EL84/5BQ5 amp? The missing suppressor connection may cause distortion, and maybe nothing catastrophic will happen. Hopefully your ears will tell you something is wrong, you turn it off, wait until the tube cools off, and you plug in your adaptor socket.

I simply made the Hazen mod, aka CCE Decware mod (Christmas comes early), with a 0.1uF cap between pin 3 (cathode) and pin 6(screen grid on 6P15/SV83) on my EL84 sockets. I can still use EL84, and the amp is now fully compatible for both EL84 and 6P15
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What happens, if you plug an actual EL83 into an EL84 or SV83/6P15 amp?
You potentially may get smoke, because that 9 Watt plate may be overheating and everything is just off, plus the pinout is different, and if anything uses pin 1 on the socket as a tie-down, you may be looking at shorts to the screen grid (you could be shorting screen to suppressor, which may be tied direct to cathode and get smoke from your PS!)

Now aside from the pinout problem, at second glance, red-plating of that 9W anode may not be a worry, because EL83 grid voltage is actually spec'd at (-)5.5V vs. the -7.3 for EL84 in class A, so plugging it in to an EL84 biased socket may work without red-plating due to the higher neg bias set for EL84, but I have not tried it, because I am not going to hunt for very rarely seen true EL83 tubes (The JJ EL844 is an EL83 with EL84 pinout and expensive!)  ;)
In any case, antique NOS true EL83 are more expensive at between 10 and over 55 bucks a piece or more than 6P15/SV83 (my brand new bulk stock Chinese tubes are fantastic at 4 bucks a piece, and look almost like Western Electric EL84 re-issues and sound a lot like them too, plain lovely)