Have any of you retubed? If so, with what, why and how did it change the sound? I just opened mine up just to see what it had for tubes and oddly enought here's what I found from left to right: no name, Sovtek 7025, no name, no name. I highly doubt the dealer I bought it from three years ago had a reason to change the tubes so I have to assume it came from Koch this way. What's with the generic 12AX7s?