do you have to bias guitar amp pre amp tubes

Swapping preamp tubes in and out and listening is something anybody pretty much can do. That said, if a tube doesn't light up replace it. If you have zero tech ability just wait for bad sound.

When noise or bad sound occurs, but 1st check preamp tubes and look for an individual bad tube and replace just the one, then listen again.It'll usually be V1. This is a good thing because the amp runs four of each of these tube types and replacement tubes now cost north of $1,000 each. I have not had to replace any tubes in the six years or so that I have owned the amp and the builder says that the tubes will last for many more years (the tubes were used, old stock when I bought the amp). For example, I know of a particular 300B amp that owners have not had to replace the Western Electric-sourced power tubes after more than 15 years of fairly heavy use others running the same model of amp with different brands of tubes have had to do more frequent replacement and with one particular brand, the tube would start to flash and make sputtering sounds after 15 minutes of operation. So much depends on the type of tube, the particular design of the amp the tube is being used in (some amps drive tubes much harder), the way the owner uses the amp and the particular manufacturer and vintage of the tube. I don't think that the idea of an average life for power tubes is at all useful.

Do you have to bias guitar amp pre amp tubes