Preamp popping!

If you’re saying that the popping has only started recently and you’ve been following the same turn-on sequence as before: Yes- It’s probably a tube issue. If it’s affecting both channels, check the rectifier. If only one channel, the signal tubes.  Those can be eliminated by swapping them from channel to channel and seeing if the pop follows the swap.

Does your pre-amp have a built in muting system that automatically engages on turn on? If so, perhaps it is failing. 

@newbee and @rodman99999 thank you.  that's the kind of input i was hoping for..

it turns out my 6V6 tube is starting to go.  i turned on the preamp and watched the tubes.  a huge arc shot from the top of the tube to the base.
i'm thinking that's not good.

so i put in the original junky one and will buy a new one.  odd, i had my pre serviced for a hum issue and since i've had it back this is the second of these tubes to go.  the tech gave me a new tube the first time it went.  this may point to a bigger issue.  or not.  i'm assuming the second until proven otherwise.

and thanks everyone, i've been on forums forever, i know how to search.. there was nothing i found specifically for my situation.  and guess what? now there is.  so the next time someone searches, this thread is another possible resource.  it's not like this forum is choked with traffic about whiners who have no idea how to basic troubleshoot.  i understand the startup procedure.  but some times i break the rules.  and when i had in the past there was never popping before.. 
i'm glad i found the source.

If its not a tube get it serviced before it blows out your speakers!!

after service or tube(s) replacement, turn on preamp first. once it's completely up, you can turn on amp.