Burn in time so far: do not recall anymore - but "sufficient" in any case
Before I comment on the tube rolling - I will let you know about the test of two gadgets I tried: 1. The use of a termination plug for the digital input on my source and 2. An "audiophile fuse" which I put into the source as well. For 1: Using a termination plug does absolutely not yield any results in my setup - but I do not recall if I disabled the digital input via the config of the Yamaha anyway. For 2: Well this may be a psychological thing since it is hard to A-B that sort of thing. But I imagine that the use of a PADIS Audio Grade Fuse has contributed to a more "firm" refined sound. At least you would not make something wrong by using it (exept for - maybe - spending money, although little - for nearly nothing).
To be absolutely sure what the differences for the tube combinations are I changed first back from combination 5 to 2 again and then back again. The result is clear: Combination 5 is superior to combination 2 in the way described already.
So the remaining combos are:
3. 7326 Cetron 1983 NOS with Amperex Bugle Boy ECC88 Holland "D" getter 1959 NOS
5. 5998 Tungsol 1963 NOS with Philips ECC88 Holland "A" frame getter 1975 NOS
6. 5998 Tungsol 1963 NOS with Amperex Bugle Boy ECC88 Holland "D" getter 1959 NOS
Now it goes into the shooutout of Combo 5 vs. 6: I have not been reporting new results so far because I did use the combo 6 quite for a long time - this alone shows that there is nothing wrong with this one. Exchanging the Amperex then with the Philips (going to combo 5) clearly revealed the airy sound character of the combo 6 but its lack of bass definition as well. I now have to listen for some time to combo 5 again - but it seams that this is a winner - better to say: a favourite. If I say "seams" that reveals how difficult a final judgement is. Both combos, 5 and 6 posess their own strengths and weaknesses (?). I would describe combo 5 as having "tube characteristics with a "transistor typical" firm bass definition" - a combination that would appeal to many I suppose. Combo 6 just gives you probably too much of that "tube characteristic" (using this term for the lack of a better expression) - but this is as well a matter of taste and it depends on the style of music you are listening to.
I may say that combo 6 is surely nothing for dance floor music, but might be more appropriate for orchestra classical styles - but then again - combo 5 will do that very very well, too. Reporting day 9 will then contain soon the final shooutout results with only one "favourite" recommendation and a summary of everything concerning my "WA3+ experience".