diytube.com

They had a post on Bob Carver selling amps on ebay at DIYAudio, and I looked on his website and on some of the amps he is making, says "Fixed Bias", "Regulated screen grids on high level speech and music", and "Cool running output tubes, expected lifetime of 50 years". How do you have fixed bias, regulated screens, and cool output tubes? Only thing I could come up with is a variable bias, but I just made that up.

Notice where the comma is in that sentence..... the tubes won't last 50 years, the amps will. It's marketing speak