Hi Guys, after a lifetime of transistor and hybrid amps I’ve finally got an all-valve head. The VB-2. Sadly it sounds crap and so I’ve got 6 new JJ EL34 Mark 2 tubes that came today. Can anyone help with two questions please? The tubes have values written on the boxes. PC and TC. What’s that? The PC values range from 78 1 to 78 7 in the second box. The TC values range from 10 7 to 11 with no value in the second box. In ordering a matched sextet are these values close enough? Secondly, having never swapped the tubes in a head before I believe the current tubes are the original set from 2008 and therefore from watching YouTube I don’t intend to do any more than swap them straight out and not mess with anything else. Any tips on this at all? Sorry, that’s a big ask but any help gratefully received. Thanks.