Mesa Boogie Question

Tubes rock! In a tube or "valve" amp. tubes  provide power to drive the speakers, as well as the pre-amp. They're the source of most highly prized guitar tones, no matter who the player is...with few exceptions.

In recent years a number of companies (most sucessful being Line 6) have produced tube amp modelling direct boxes, amps and software. These models literally mimic the characteristics of the amps being modelled. Opinions vary, but a lot of notable names (like Les Paul!) have been seen using modelling amps. Personally I use a Line 6 POD xt modeller into the power amp in on my old acoustic 165 tube amp. The tone is wonderful! On its own the POD sounds very good, but putting it through real tubes is ecstatic....

Any modern tube amp will typically use easilly avaliable tubes. I've yet to see a music store that sells guitars not carry tubes. Prices vary widely, so definately compare. Depending on the types of tubes you may need to have the amp "biased" which can be done at many music stores for a nominal fee. It's best not to go poking around inside your amp if you don't know what you're doing; there are lethal amounts of eletricity in sections of tube amps, even when unplugged.

Rules of thumb for changing tubes...some people swear by every six months, some have to be changed if they turn "microphonic" (you'll know; howls of unwanted feedback and occasionally picking up noises from the room) or if they have an unusual purple glow which coincides with unwanted distortion...

Good luck!

actually the amp will come with tubes from the factory...I wouldn't worry about changing them unless they start producing the afore-mentioned symptoms...

The latter. Unless you're playing like, 8 or 10 hours a day you shouldn't worry about changing them sooner than a year after you buy it....