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.

Joe Robinson

Joe Robinson plays guitar like Ali boxed, like Einstein knew theoretical physics and like Hitchcock made movies. If the chipper twenty-year-old from backwoods Temagog, New South Wales, Australia were two or three times his age, his sheer six-string ability and compositional insight, which have already earned Robinson a world-wide following, would be no less astonishing. That fact is underscored by his winning TV's Australia's Got Talent in 2008, and the Australian National Songwriting Competition at the tender age of 13. But with his new album Let Me Introduce You, Robinson has made a daring quantum leap. The gifted young virtuoso has redefined himself as a budding pop-world visionary, deftly walking a tightrope between the instrumental music that's put him in the spotlight and a unique fusion of vocally based rock, blues, jazz, country and R B that's entirely his own. "Let Me Introduce You was a dive into the deep end for me," Robinson confides. "It would have been easy to make anothe...

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