Music Man Amps

Kind of hard to tell actually. There were factory units with the same setup. Sticker and plate. They used up the chassis that they had and had the cabinets made and used up the stickers too. Then there were the factory conversions that people sent in when they were having red plating problems ( I had one of those), then there were the "kits" that they sent out to people and techs to convert over themselves. I did one of those also. It involved removing the 12ax7 and using a plate provided by the factory and the massive re-wiring of the chassis to completely change the structure of the amp from a fixed/adjustable bias amp to a cathode driven solid state driver circuit. Don't know how to tell you which you really had. Chances are though, it's factory and they were just using up the stuff. The outside conversion was very involved and most places probably wouldn't do it on an outside basis and most individuals wouldn't have the patience, time and skill to do it themselves. That's my story and I'm sticking with it! Mike.

If one is to believe the old brochures and what little info is available about the internal practices of MM, the metal chassises were made in-house. I've thought about the tube socket cover plate a few times too - the later solid state driver units also had this - and not only the 65/130 version, the later 75/150 had them too. Whether all of the later models had them, I don't know of course. I'm thinking that when they switched to the solid state driver setup, which was invented to address a stability issue not as much as improving on the overall sound, the chassis design was adapted so old stock could be used and existing units could be converted. In the end, they just stuck with this way of doing it, maybe it was cheaper to just keep it that way.
I know that doens't answer padzor's origninal question - my own suggestion is along the same lines as Mike's. If the chassis appears to be totally untampered with inside, it's probably either 100% stock and the tube sticker is a leftover, or the entire amp chassis was swapped out at one point in time.

As per usual, my advise is to play and enjoy :)

Happy Friday!

-Lars Verholt

As I think back to the 70's (OH MY GAWD!), I seem to remember getting amps in with the ss driver installed and still having the tube listed on the sticker. I think that the Leo mentality was to waste NOTHING! Mike.

I'm drifting a bit off topic (something I seem to do often..) but I'm curious about Music Man switching from the 12ax7 to using a ss driver. Where they having a lot of problems with the 12ax7, or was this just a preventative thingy?
I've never heard of, or seen any 12ax7 melt downs around my neck of the woods but, I haven't seen that many MM amps around here to start with. Thanks, Dave.

They had a bad habit of going Chernobyl on you. I HAD one. It would light up the power tubes like a Christmas tree. I think the biggest reason was they were running out of GOOD tubes. I had one that had GOOD sylvanias and it would eat them regularly. That was of course when they cost $2.50 each though. It was no big deal to get a new set other than they seem to go to crap right when you didn't need them to. THAT'S why they went to the SS driver. It did change the tone of the amp though. Also why the 12ax7 need to be a good one and bias them cooler than normal. Mike.

Wow, that's not a good thing having your amp cook it's tubes at anytime. And you know, there never is a good time for sometime like that to happen, yikes. I can understand why they went over to the ss driver.

Thanks Mike for your answer. Dave.

The sad part was I was trying to SELL them at this time. That's why I bought one then. It was a PITA for a while trying to sell them when I knew they had issues. After they went SS, no more troubles. Sold my "twin" sixed MM and later went right back and bough the 2-10. Go figure. Mike.