A Little Help With My Studio .22 Required

overturned · Jun 5, 2006

Hey, my first post here.

I just (well, about 6 hours ago) got my Studio .22 combo. And I'm really happy, the first Mesa I've ever owned and it probably won't be the last.

However, I'm having a little trouble. As, sometimes its feedbacking a little unnescesarily. According to the manuals of .22+ and Caliber (I couldn't find one for the .22) it reccomends switching out the pre-amp valves.
Now, I'm no newb to tube amps, I've owned a couple, but this would be the first time I'd be interested in replacing them.

Would y'all agree with the small amount of info I've gathered over the "problem" that new pre-amp tubes would be the solution.

And will I need to take it to a tech for biasing of the pre-amp valves?

And, on a similar theme, when I arrive at the stage where I would want to replace the power amp tubes would they then need to be biased or is the amplifier "fixed bias".

Many thanks

RR · Jun 5, 2006

Your preamp(s) tube has (have) become microphonic and usually the culprit is the V1 tube socket the one closest to the input jack. Exchange that with a new 12AX7. That may cure the feedback.

Other may chime in making other suggestions.

plumptone · Jun 5, 2006

Congrats on the new old amp. I used to have a studio .22. Great little amp. I wish I never sold it.

Pre-amp tubes should be checked definitely. It probably wouldn't hurt (if you don't know the age of the tubes or how hard the amp has been worked) to do a complete re-tube on the amp. That way you are starting with a clean slate. But in any event, there's no need to re-bias the amp - it's fixed bias, and deliberately designed that way. A new set of good tubes and the amp will amaze you with what it can do. If you haven't tried it yet - run it through a 4 x 12 cab. You won't believe your ears.

LHanson · Jun 6, 2006

Nice amp. I have a .50 cal +, a .22's big brother. Same preamp (or nearly so, depending on if it's got a + or not).

Preamp tubes don't have adjustable bias circuits, they are cathode biased, so don't worry about the pream bias. All Mesa's have fixed bias output stages, meaning there is no adjustment, just buy the right (according to Mesa) tubes.