What is bias a tube amp ? Is it difficult?

In the back of my mind when I purchased my tube amp, I too, dreaded having to bias my VTL ST-150. But I wanted tubes and like anything else, I knew I'd eventually learn how to.
I had the bias instructions and I bought a decent multimeter at Radio Shack. When it came time to replace the tubes, I called the dealer, CSA in Montclair, NJ. I explained my inexperience and the dealer offered to bias the amp and show me how easy it is.
He was right. I took notes, paid attention and since then I've performed the operation myself. Go ahead, don't let the unknown keep you from experiencing "all" aspects of this hobby.

Fyi, Decware makes terrific tube amps and preamps, and they are all self-biasing. Check out Decware.com .

Good luck

Find out ahead of time how to bias the particular amp you're looking at buying - they are all different.
Some auto bias, so it's a total non issue for the owner.
I have a Rogue Zeus, which has a LOT of tubes. Rogue puts a meter right on top, built in. You just flick a switch for the tube you want to check, and adjust. It's that easy. Rogue might do this on all of their amps, I'm not a dealer - I don't know.
In my mind there are some advantages of being able to check bias - you should let the tubes warm up for a while before checking - auto bias checks them at the power up cycle. Also, you can check tubes periodically, and see if one changes faster than the others, and is on the way out.
I use my amp daily, and need to adjust them every 4 -6 weeks - but not by much. You feel like you are giving the thing a tune up - which I guess you are!

Biasing is NOT difficult. Own a JoLida 502B.

I don't understand auto biasing vs manual biasing? Why wouldn't all tubes be auto/self biasing? What is it about the nature of an amp, or the manufacturer, or whatever, that one would produce an amp without this feature? thanks in advance, warren :)