Inherited a stack of old NOS (some used) tubes.

[lastmile]

I found 10 Mullards EL34 (xf2) they seem in good shape and they were kept in boxes since the 60s or 70s. I have yet to test them. There was also some other cool stuff in there, such as a few Mullards EL84 (from the same era).

Does anyone think I should pop these EL34s in my Mark III or IIb (whould need mods I guess), or trade them for something else ?

any ideas, experiences?

 

[Boogiebabies]

I would have them tested and batched before I made any speculation.
You may have a few duets, or luckily a quad that are within 5ma of each other. The other issue is the tubes natural plate current. If the tubes draw too much, you could possibly end up running your rare XF2's too hot, perfect or cold. A 25 watt tube should not see much more than -40 ma on a 460 volt plate supply. After they are graded and if you have any matches, a bias meter would be needed to read the actual current draw while the tube is installed. Anything betweem -20 and -42 should be allright, but -45 and up is getting closer to the tubes maximum capabilty and will shorten it's lifespan. A good Mullard run properly should last for an inhuman amount of time.

 

[lastmile]

Thanks for the info BB. I will have them checked out later today.
If I am lucky enough to get an ok matched pair:

1- Is it even a good replacement for the current JJ 6L6GC that are in my mark III? or should I trade them for something else?

2- What are the the top 3 best power tubes that I should put in my mark III? What about the top 3 best pre-amp tubes for this same combo?

 

[stokes]

Mullards are pretty much the "cream of the crop".If you have a Bias-Rite or some other way to test the current draw you can match them up within 5ma's like BB said,but dont just pop them in your amp and hope for the best,make sure they are within the proper range for your amp first.Like BB says between 20 and 40ma's in your boogie is okay,have even seen EL34's lower than 20ma's used in simul-class and still sounded okay.Even used Mullards if they werent abused and completely worn out,will bring a good price or give you an excellent tube to use.If the used ones were used in a Hi-Fi application they most likely were not pushed hard and will have plenty of life left.Have them checked for current draw in an amp with the actual voltage they will see in use,just testing in a tube tester is not sufficient, will basically just tell you good/bad.You have a possible treaure trove there,good luck with them,be careful trading them for "new"tubes,like I said even used Mullards bring a steep price.Nice find.