The extended upgrade increases the gain of the circuit a bit. So what probably happened is that the noise floor of the tubes was amplified a bit more than it had been without the upgrade, thus making the noise more noticeable when music is not playing. Putting in different tubes verified that it's the tubes and not the upgrade that is creating the noise - unless the gain seems much lower with the cleartops than it does with the Psvane. You might try using the cleartops on the outboard positions and the Psvane in the center position and vice versa to see if the noise is more obvious wit the Psvanes in the preamp stages or the regulator stage.
Does anyone know how to pronounce Psvane?
No no no, it's spelled, "Raymond Luxury Yacht," but it's pronounced, "Throat Warbler Mangrove"
- Raymond Luxury Yacht