My Rig

Randall Pro-Tube 1000 (early model, have yet to find any info about it online)
Running through a Behringer Time Machine Pedal, and a Boss DS-1.

Powering both of those pedals is a OneSpot 9V power supply with a chain for extra inputs.

The problem I've come across is a new one for me. I've had the amp for years and never seen this happen.

The Problem

Basically, my amp sounds like it has a tube problem. I warm it up, turn it on, start playing only to hear a SEVERE reduction in volume and quality. It sounds thin and clipping, almost like it's running through a solid state on low volume.

Looking at both tubes, they appear to be perfectly fine at a glance. The pre amps are all lighting up and nothing is glowing out of the ordinary.

Here is the bizarre part: I think it has something to do with plugging in my OneSpot.

I tried bypassing the pedals and plugging straight into the amp. I still hear the same problem.

However, once I UNPLUG the OneSpot from the wall (after turning the amp off), I turn it back on to hear my amp back to normal. Although, I also hear a bizarre clicking coming from my amp at this volume.

So why would plugging my OneSpot (that isn't even powering anything) into the same outlet drain the power from my amp?

To be safe, I've tried three different outlets in my house. The same problem.

Does anybody know what could be wrong here? Thank you for the help. Sorry if the post is a little wordy, it's a bizarre problem.
Yeah, uh-huh...that's what they all say.
Could be the phase inverter. Try changing that first, it's cheap.
Gilchrist custom
Yamaha SBG500
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100

Cathbard Amplification
My band