New tube from Russia. Slightly brighter and lower gain, quicker compression than GT 12AX7. Great for most Fenders, may not be well suited for high gain Fender type amps (such as Boogie).
The Groove Tubes Warranty
Warrented to be free of burn out, excessive noise or microphonics for 180 day from date of purchase.
Warranted to be free of burn out for 90 days from date of purchase. If one tube fails, the whole set will be replaced to insure proper matching.
GT-Solid Rectifiers & Substi-tubes:
Warranted for 3 years from date of purchase.
The Groove Tubes Process - Step by Step
Testing and Selecting Tubes.
Groove Tubes literally goes through thousands of tubes, rejecting more tubes than they accept. They put every tube through a rigorous performance test, one at a time, in real amp circuits. The preamp tubes are rejected for adverse microphonics, low output or high noise. Power tubes are more involved, and they go through additional testing. Here's what they're looking for:
- Grid Leakage. Causes tube to burn out quickly, and worse yet, to short out and wreak lots of havoc. They throw these tubes out.
- Weak Vacuum. Tube will act deceptively normal, then just burn out on you (usually at the worst time!). These tubes don't make it past the first round.
- Gain to Distortion Ratio. The center of all Groove Tube magic! This measurement tells us if the tube will distort early or later in its power range. Since the tube distortion is rich in harmonics (That's why we love 'em!), the tonality of each tube will vary according to this ratio. Only Groove Tubes sets have been measured and matched to insure longer sustain, wider frequency response and a more musical amplifier!
Rating and Matching Tubes.
Groove Tubes translates this gain to distortion ratio into a performance scale that can range up to 100 points, then match up the tubes to within 1 point of each other. To simplify things, they reduce the scale to 1-10 before the tubes leave their shop. All tubes are exactly matched into duets, quartets, sextets and even octets.
More than just Great Tone.
The Groove Tubes Process produces many welcomed improvements:
- Dramatically Improved Sustain by eliminating phase cancellation (which occurs when dissimilar tones coming from unmatched tubes are combined and cancel out certain frequencies.)
- Improved Harmonic Balance- All the notes you play will have the same amplitude. (No more dead spots or dull notes!)
- Longer Life Span by 1st) eliminating faulty tubes. 2nd) Their balanced sets reduce stress that occurs when a stronger tube is working too hard to make up for its weaker partner, and 3rd) because their sets drive the output transformer evenly it actually runs cooler!
Groove Tubes. It all Comes Down to Tone.
When you go into a store and buy other tubes, it's a crapshoot. Without The Groove Tube Process, there's absolutely no way of predicting how a tube will sound. When other tube suppliers claim to have "matched" sets, they're referring to the meaningless measurement of the tube's power. As we learned in the beginning, it's a waste of time to measure power because you simply can't hear variations of power (unlike variations in harmonic distortion). And even if you could, the power measurement is always changing as the tube wears (This measurement wouldn't stay "matched" anyway, but theirs do!). Buying Groove Tubes will save you money and a great deal of aggravation, while turning you on to the best tone you're ever heard coming out of your amp! Groove Tubes are more expensive than most other tubes. Now you know why.
The Tube-Tone Phenomenon. The next time you're experimenting with your tone, and before you shell out more bucks on effects, gadgets, guitars, another amp! ... check your amp head and try out a new set of Groove Tubes.