Power tube with low output (12 - 18 W) often used in Fender amplifiers, including the Champ, Deluxe, Dual Professional, Vibro-King, Princeton, Vibrolux and others. It has a very warm, round and soft response with rich harmonics, and distorts easily. One of the best choices ever produced for rehearsal and recording amplifiers. Our most premium design, for long life and professional performance. The choice for many pro players who use Groove Tubes in their favorite amps for recording and rehearsal; fully captures the spirit and sound of tube amps from the ’50s and '60s to the present. Matched pair of 6V6-S tubes rated from power range 1-10. Each pair has a specific rating (i.e. R2, R7, etc.) and is matched and biased to a specific output level. R1-R3 Low: Early distortion, wide range, softer attack good for Rock and Blues solos. R4-R7 Medium: Normal performance, great dynamic range/attack and best all around rating type for all styles of playing. R8-R10 High: Most dynamic range, most clean power/less break-up for power players, Jazz and bass amps.