How can you tell when you need to replace tubes?

A couple of years back I picked up a Superior TV11 tube tester on eBay for $40 or $50. Not the fanciest tester in the world (it is just an emission tester) but it works for my purpose.

If you decide to buy a tube tester I would recommend you educate yourself about the different types and watch the auctions so you can bid intelligently.

With break-in often reported by audiophiles to be up to 1000 hours and power tubes lasting about 3000 hours it would seem to be a critical question that demands a precise answer. However, precision audio is a bit of a mystery - like cooking a great meal - sometimes it turns out just fantastic and other times it just doesn't cut it - even carefully following the same recipe.

I did not realize that tubes take 1000 hours to break in until I experienced it my self. I can say it has been that long, but the tubes sounded harsh and cold at first. Now the EL tubes sound very detailed with good layering and seperation, plus there is no harshness or distortion like at first. I though EL tubes were not very good until many hours were on them.

Thanx,