Ok, here is the deal. I have the 100 watt Plexi RI and bought some power tubes that should have biased easily at 38 ma in the low 400 volt range. Even with the pot adjusted all the way I can only get 30ma's........ What do you think it is? Basically the way I understand it is that the SLP has 2 pots. VR1 and VR2. One is for the bias and one is for noise. Correct?