Sonically the greater effect is always the driver tube, compared to output tubes.
NOS EL84 should remove the four jumpers. They should also be fully tested, including at rated voltages, to be sure they work 100%. Given how desirable a tube the EL84 is (use with many different home and guitar amplifiers) it is EXTREMELY UNLIKELY to get good quality NOS tubes.
There are generally two possibilities for western NOS versions of popular tubes – they are rejects of multiple selection rounds, and are in effect the remaining rejects. In which case, often the performance is not acceptable, or they are outright fakes (which should be avoided at all cost). It is not possible to exclude 100% the possibility of buying good NOS EL84, but it is very small.
On the other hand the ECF82 is primarily a TV tube, and rarely used in audio (though it is very similar to 7199 which is a widely used audio tube and hence again extinct in NOS). So large NOS stocks of good tubes remain.
We would suggest to leave the EL84X factory supplied in place, and only use NOS options for the ECF82. There multiple equivalent tubes, any tube equivalent to ECF80 generally also works in place of the ECF82 in our circuit, but has slightly different operating conditions, and hence sound quality.
Please note, any tube rolling will void the warranty.
