In my parts bin I have left a couple of transformers: PT 160-0-160 and 6,3V 4A secondary (it should be good for an amp with a quartet of el84) and OT Single ended 6600 Ohm into 4 or 8 Ohm 15 watts. I would like to build 6L6 single ended bass amp for a friend, but the voltage the PT puts out is too low. Would it be possible to use a full silicon rectifier and voltage doubler to get around 400V for the power tube? Can you point me to a schematic? Then, since this will be a bass amp, I am thinking about the pre... I don't want to add a lot of knobs, so I wonder if a baxandall eq and just a volume control would work.