@thewatcher101 - Please list the pre-amp you are using.
@thewatcher101 - The Pathos Aurium is a headphone amp. I'm not familiar with it, but I looked it up. The only "outputs" it has are for headphones, plus an 1 XLR and 1 RCA "Tape" output. In this unit, I'm not sure what the difference might be for a "tape" output vs a traditional pre-amp output. I'm not sure you are using it as intended and I'm not sure any advice you may get will be valid considering it is not a traditional pre-amp.
Just curious, how do you have this connected to the amp that powers your speakers? What amp are you using?
The Pathos Aurium is a headphone amp, not a pre-amp. I read the user manual. According to the user manual, the "tape" outputs are a bypass. To me that implies that the tube and headphone amp are not in the circuit at all if you use the outputs.
I suspect you may not be using the Pathos properly. That would explain why you don't hear any difference when you turn off the Pathos.
How are you "skipping" the tube in the pre-amp"? Are you turning off the Pathos?