Originally Posted by: JFRICKAnd remember that power amp tubes (valves) should not just be replaced. You'll need to have the amp re-biased for the new tubes. Failure to do so may cause damage to the amp. This is not a do it yourself thing, take it to your tech for re-biasing and re-tubing. Pre-amp tubes can just be replaced, they don't need any kind of adjustment (biasing).

Isn't it possible to get color matched groove tubes, so you can change the tubes yourself. my fender delux came with tis type of tube and recomends that if I order the right tubes I won't have trouble with the bias.