I use all GE 12 type tubes in my amps and that loud cracking sound is a tube failure. The seller is giving you a line of BS!
must you play music to break in tubes
I have some GE 12ax7 longplate tubes that make some loud crackling noises. The Seller claimed that this is common with nos tubes and that it will go away after they are broken in, but it is too alarming to hear and sounds risky to the speakers. Might leaving the amp powered up for a while, but with no signal passing, break them in adequately? Kind of hate wasting the power tubes lifetimes, but I don't have any old tubes to use in that amp.