I'm not planning on halving the price if that's what you are hinting Well the previous owner must simply have preferred EL34's. Yes, it is simply the effect of flicking a switch to change it from EL34 to 6L6. It had the EL34s when I got it, I used them for a month or so, then changed them to 6L6 (to see what they were like, and also because I had a talent show to play and wanted them to be in full working order, so as a just in-case). I've had the current valves in for 10 months and they still sound good. I've had not one problem with hums or crackling or anything either. Yeah that's pretty much it regarding the valves! Couldn't really put it much simpler!