I have some tube rolling questions. 1. If you are tube rolling but are only replacing one pair of tubes, is it the two on the left for the left headphone jack? 2. When you use the bias adjustment, is there a separate way to do it if you only change two of the four tubes? 3. what plate voltage and plate current to you get on the tubes when you perform the bias adjustments? I'm still looking around the different threads but I have not yet found an answer to those ones.