What's wrong with my recently upgraded rig?

[ryansalmond]

I was going to do a bunch of soundclips, but then I realized it basically comes down to this:
-when any instrument is plugged into my amp, there is a light hum.
-when my signal chain is bass>pedals>amp, the hum is louder, and there are lots of really loud popping sounds.
-when my signal chain is squier strat>pedals>amp, there is still the light hum, but no popping noises.
-when my signal chain is bass>amp, there is only the light hum, no popping noises.

Background: I have recently bought a lot of new gear, including an acg on-board preamp and several pedals, one of which (an EHX hog) needs its own power supply. When I got this new gear is when the problems with humming and popping started. A couple days later, my amp's sound had become reduced to something very quiet and fizzy. I opened it up and noticed one of the preamp tubes had gone powdery. I replaced both preamp tubes with tubes of the same kind. This gave me my sound back, but the hum and loud popping are still there.

Things to note:
-all the pedals are plugged into a godlyke powerall (one spot), except the HOG which has its own wall wart, and an EHX Steel Leather which I power by battery (got it a long time ago and it's ground has never gotten along with the other pedals).
-Everything is plugged into one power bar.
-the onboard preamp was installed by a tech, but left two extra holes in the bass as the previous preamp had more knobs, and because the input from the old preamp had a bigger housing than the new one. I've attached photos as this is hard to describe.
-There is no shielding foil / paint inside the bass's cavity (unless such paint had been covered by regular paint?).
-While the preamp tube that was emitting white powder obviously needed replacing, I didn't get my sound back until I replaced the OTHER tube.
-Before replacing the preamp tubes I tried plugging into the return jack of the effects loop, thinking this would bypass the preamp tubes and connect me straight to the power amp, but still only got quiet fizzy sound. Afterward, the guy at mesa said that "one of the preamp tubes is a phase inverter that is before the power amp."

Could my new on-board preamp's ground not be getting along with the grounds of my pedals?

I'm not sure if all this means I should get a pedal power supply with isolated outputs, or if I should shield my preamp cavity, or if there was damage to my amp beyond just the preamp tubes.

I hope I've posted this in the right place. Any help will be greatly appreciated.

[ClaytonH]

Try shielding both the contrl and pickup cavities.

[Son of Magni]

This should be in setup & repairs...

[Basschair]

I was thinking Pups and Electronics.

[ryansalmond]

Will shielding help with the popping though? I thought that was just for electrical hum.

[boogie8008]

if the popping is only present with the pedals in the chain the problem is in your pedal board. run one effect at a time to figure out where the problem is and report.