Many folks who buy our tubes know that we use a special process to categorically rate our tubes so that players can select the tubes that best fit their preferred tones and styles. However, we get a lot of questions about our rating system, and what the numbers actually mean.

IMPORTANT BIAS NOTE: If you're replacing a tube with the SAME TYPE of Groove Tube (tube model and rating), you do not have to rebias your amp. In any other case, you should always have a qualified amp tech reset your amp’s bias whenever changing your tube type or rating number.

low

1-3

Early distortion, wide range, softer attack good for Rock and Blues solos.

Medium

4-7

Normal performance, great dynamic range/attack and best all around rating type for all styles of playing

High

8-10

Most dynamic range, most clean power/less break-up for power players, Jazz and bass amps.

Jason Hook / Five Finger Death Punch

Jason Hook started his music career at the early age of 6 in Toronto, Canada, with private guitar lessons. His early experience in formal music training also included drums, piano and violin. After working hard for many years honing his craft, In the late 90's, Jason relocated to Los Angeles and went on to tour and record with many acts, most notably, Alice Cooper. In 2007 Hook released his debut instrumental hard rock metal album, Safety Dunce. It garnered industry praise and an L.A. music award for "Best Instrumental Record" of 2007. Shortly after, Hook embarked on a two-year touring commitment with rock legend, Alice Cooper. During this period, Jason recorded his second solo release, American Justice which featured a guest appearance by Alice Cooper. On January 30, 2009, it was officially announced that Hook would be joining Heavy Metal buzz group, Five Finger Death Punch. Shortly after, Hook and his bandmates hit the studio to write and record "War Is the Answer" released Sept 22nd...

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