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.



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



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



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

J Mascis

Indeed, Mascis is one of today's foremost exponents of the Jazzmaster. A surf staple in the'60s and a punk fave in the'70s, the guitar had become something of a fringe model by the 1980s. But the Jazzmaster was given new life in the'80s,'90s and beyond by Mascis, who took the instrument to a new place with his feedback-drenched, distortion-laden band, right-coast grunge pioneers Dinosaur Jr. Mascis (born Joseph Donald Mascis Jr. in 1965), bassist Lou Barlow and drummer Emmett "Murph" Murphy came blasting out of Amherst, Mass., in the mid-1980s with their debut album Dinosaur blazing an acclaimed indie rock trail with albums You're Living All Over Me (1987), Bug (1988), Green Mind (1991),Where You Been (1993), Without a Sound (1994) and Hand It Over (1997). Mascis assembled a new band, J Mascis and the Fog, in 2000, but when Dinosaur Jr. came back from extinction for a 2005 tour and released a new album, Beyond, in 2007, Fender knew it was high time to recognize one of its rare Jazzmast...

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