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.

Nils Lofgren / Bruce Springsteen & the E Street Band

Nils Lofgren - acclaimed guitar master, successful solo artist, Neil Young sideman at age 18 and guitarist for Bruce Springsteen and the E Street Band since 1984. That's some r sum .Born in Chicago in 1951, Lofgren took up accordion at age five after his family moved to the Washington, D.C. area. Something of a musical prodigy, he studied music throughout his childhood - including classical and jazz - and took up guitar and piano after being smitten by rock music. He formed popular rock band Grin in 1969 in Washington, D.C. before joining Neil Young at age 17 in time to play piano on Young's landmark After the Gold Rush album (1970), despite having no experience as a session keyboardist. Lofgren also briefly joined the band that Young had enlisted, Crazy Horse, and played on the group's famous eponymous debut album in 1971.Lofgren also played on Young's Tonight's the Night album and tour (1975), Trans (1982) and Unplugged (1993). Lofgren has maintained a good relationship with Young al...

View Artists Profile