Just for information - a collection of various user posts....
"I think that the Sovtek EL84 sounds great. NOS is good, but the Sovtek is underrated by tube sniffers, though generally respected. I like the EL-84M, military-spec version of the standard Sovtek EL84. Sovtek EL84M's extended voltage tolerance - improved plate dissipation - and ruggedised construction make it equivalent to the RCA 7189. EL84M have higher transconductance, more power and longer life than the standard EL84. However, some musician's prefer the regular EL84's warm distortion to the EL84M's tighter - cleaner tone. For hifi go for EL84M
Jim McShane likes Gold Lions: "Construction quality is superb, and the performance on the test bench looks great. The reviews are very positive as well! Clearly this is the best new production EL84."
Genalex Gold Lion EL84 reissues - sweeter treble than Sovtek or NOS military EL84 which can sound slightly steely. Bass is tight and mids are beautifully clear. Some QC issues, I had some fail in under a year, though my current pair last 4 years or so.
Psvane EL84s, a magic combination in my amp, a lovely 'tone'. QC seems better than the Gold Lions, but they cost twice as much. With the Psvanes in my Glow amp, the treble was a bit soft and lacking in bite, and the bass wasn't well defined.
I too vote for the JJ's. Ruby EL84 is made by JJ.
Tried JJ EL84, EI EL84 (now scarce) and a Russian mil spec EL84/6P14P-EB in a Manley Stingray amp, all fine. A slight preference for the JJ followed by the EI followed by the Russian 6P14P-EB. JJ EL84 are good value.
Some NOS EL84 in triode mode sounded GREAT, 6P14P-EV and 6P15P-EV sounded just good, but nothing to write home about.
NOS
Best are Mullard cv2975, Brimar el84, Telefunken 7189 and surprisingly RFT. I kept some Reflector 6p14p & 6p14p-ev , EI Elites, Siemens E84L/7320 and Sovteks which I listen to every now and then, but I always go back to the "selected group" above.
Any GE and RCA sound great and last forever. For a little more cash try Philips Black Plates and Mullards. Stay away from the Teles, their el84s are some of the worst tubes they made and fetch silly prices.
GE 6BQ5 is the best one. Russian military ones are decent, but not as good.
I have RCA metal case 6V6, nothing special. Siemens EL84 is much better.
Telefunkens which I am using now. Great detail with super wide soundstage. Not too different from the Mullard 7189. Jim Hagerman.
Tung-Sol 7189 are excellent tubes for this amp, exceptional low end. RCA grey plate 7189 or just regular EL84 are also nice. EI El84 is also great in midrange and lower mids. I’m now running a pair of ‘57 Amperex 7189 rare D getter and I think my tube hunt is over. These are the best mix of high, mids and lows in my tuba.