I have a little Bellari tube phono pre (the VP-530 - which is pretty much the WP-129 with an added usb out), and I decided to give a different tube a shot. I wanted to start cheap, so I went with the Sovtek 12AX7LPS, becuase some people had reported improvements over the OEM tube, and other sources suggested this one should be pretty quiet and is good for use in phono preamps.
Question: Do tubes need to be broken in before a judgment is made and, if so, how long? Also, when "breaking in" is mentioned in some components, some people say it is a myth. Is this the case with tubes? Also, is there a known science behind whether they need broken in, or is the notion based primarily on anecdotal experience? It's okay if it is, I'd just like to know. I don't want to start a debate on whether it is "real" or not; rather, I'd just like to know whether there is a consensus and, if so, what that is.