fxloop

So I got a new noise gate pedal (Klirrton Schnauze, it's pretty great). When I use it with 4 cable method it's all fine, but when I use it 4 cable method with a preamp pedal into the fx return, there's a huge level boost. (guitar > schnauze input > preamp pedal > schnauze loop input > MT15 fx...

I ran into the oddest and noisiest hum on my MT15. Now the noise only starts when I run effects through the FX loop, I have tried the same setup though my Mesa and do not get any noise, but when I unplug the chords in the loop the noise goes away. Ive replaced the preamp tubes so I don’t feel...