Good to hear you isolated it to the pre. Like I stated in my response earlier, always turn the amp on last. I would fix this issue though ASAP as it can, if you allow it to get worse, potentially take out your amp or your speakers or both. Good plan to start with a fresh set of tubes.
System Static Issue
Have an interesting situation in my system that I have at my work location. The system is leftovers from other upgrades but since it is used primarily as background it fullfills that quite well.
Recently, when I start it up in the mornings, while the preamp is in mute mode and volume is at 0, with no input signal, I will get a static sound out of both speakers, intermittent, but there.
I am assuming it is the tubes in pre (ARC LS17 se)
Have checked all connections and moved each (without static) to make sure that was not the problem.
Set up is used either to stream from internet or through a PSA Jr from SSD with music library on, through JRiver.
Before I get new tubes wanted to see if there are other issues I should consider.
ARC LS17se
Bedini 100/100
PSA DSD DAC Jr
Shahinian Arc
Furman Power PL Plus