#1
I have a Crate BV120H all tube head, with four 12AX7 preamp and four 6l6 power tubes. Recently there's been a very loud/annoying static and buzz to it whenever I don't have a noise reducer on.

I have my NS2 x-patterned through the loop and through the front of the amp. Whenever I turn off my loop, the hum/buzz is present. Does this mean that the preamp tubes are the ones I need to replace?

Keep in mind this amp is 10 years old and have about ~70 hours put on it, half of that coming from me in the past couple months.
#2
It could be a bad preamp tube. That is pretty easy to check. If the power tubes were dying then you would get drops in volume. It could still be something else but let's start with the preamp tubes. Follow my video link below and report back.

http://s545.photobucket.com/albums/hh384/buckethead_311/Amp%20stuff/?action=view&current=Microphonicpreamptube.flv

Preamp tubes are $10 - $20 each. You may only need one. Contact:

dougstubes.com
thetubestore.com
tubedepot.com
#3
Thanks a lot for the video! However, I'm stopping by my local store tomorrow and will talk to the tech there. I really wouldn't mind swapping them all out at once, but I understand that I don't want to spend more than I have to.