Musicians who get the D.I.Y (as in Do It Yourself) urge can find their first forays into tube amp maintenance a bit daunting, and in some cases even a bit dangerous until you know what you are doing. Gearwire's Joe Wallace asked Sam Austin of Groove Tubes for a bit of advice on replacing tubes and much more. In part one of our look at tube safety, why the preamp section is more beginner-friendly than the power section, and what those Groove Tube numbers (from one to 10) mean in terms of tone for different musical genres.