So about 2 weeks ago my musicman hd130 amp started to kind of crackle out on me, and I bought it a few months ago and never brought it to a tech (I know, a mistake, but the guy I bought it from worked on amps himself so I wasn't too worried.) I took out the chassis and noticed some of the tubes defenitely looked bad and when I took them out 2 were in rough shape and 2 looked good so I ordered 2 EH 6CA7's off the bay and tried to get in touch with my normal tech, but I couldn't reach him for a week so I decided to try a guy I had heard about that repairs amps and specializes in mods. I brought the amp to him and he seemed to really know his stuff, but he said a few things that I am worried about, not to question his knowledge, but it just seemed a little weird. First off... the two tubes that I thought were good werent so I have to order another pair, but he said I could now only run the amp at low power (the hd130 has a switch for high or low power, I used it on high before). He said the amp runs at about 700+ volts on high which is way more than any modern day tube would handle and it would possibly ruin the amp. Does this sound right? The low has about 300-350 volts, he told me never to run it on high, and I'm pretty sure he meant when it had all the tubes in it as well. Also, he was running the amp with just the two tubes (two middle tubes) in it out of 4, but he said it was fine for the amp, but I've heard its bad for it, is he right? Also, it obviously didn't sound as loud as it did before on high, but I'm looking for a really loud sound, and I asked him if it would be louder once the two other tubes were put in and biased, and he said probably a little, but not much, but it seems like this should double the watts going out the cab, since I am doubling the amount of power tubes. Is he right though? Will the full set of tubes not make that much of a difference? I do trust this guy, but I just wanted to check with some of you to see if he knows his stuff. He did a great job with the mods though, and he's real cheap (4 tubes biased, pots cleaned, and 2 mods to the amp for $25 flat). If anyones in the MA area, you should go to this guy. Any and all help is greatly appreciated.