I've been using my Deluxe with a pair of 6L6's instead of 6V6's. I took it to a local tech for rebiasing when I made that change. Today I called him to let hin know that I might go back to the 6V6's and he said there was no need to rebias when doing so because it is silver face. Is this right? Don't I needto rebias it when going from 6L6's back to 6V6's?