If it's crackling/static then you probably have a tube that is intermittent or has a short. I ran into this a couple of times back when I had a Woo amp. Cleaning the pins and the sockets is step one, getting yourself a different pair of driver tubes is step 2. If it is still there then you may have power supply noise leaking into the circuit or a bad cap somewhere.
Hey thanks for the reply! The noise only happens as it warms up and then doesn't happen at all.
I have a GZ34 and two 7N7 <-> 6DE7. I have a few older tubes that I had swapped for these around somewhere that I could try and see if it is indeed a tube issue.
Do you have any recommendations on how I should go about cleaning the pins and sockets? I would hate to accidentally do more harm than good.
I don't think it's PSU noise or anything like that. If I turn the sound up high enough I can hear a hum but I definitely don't play it at that volume so that's not an issue. This is a distinctly scary sounding electrical noise as it warms up. Quick burst, maybe 3-4 as it warms. I warmed it up with the headphones unplugged and only plugged them in after this time and it made a quick pop sound as I plugged in but then nothing afterward, which I assume is more normal.