The 12AX7R is Groove Tubes' take on the classic Russian sounding tubes. The Russian tubes are known for having higher quality control standards and a darker lower gain tone.
Groove Tubes has some issues a few years ago, but I feel they are back on top as far as mass produced tubes go.
The preamp tubes in a my bass amp went bad and I had to get something new. My local shop had a Bugera tube, an Electro Harmonix tube (what was previously in the amp) and the Groove Tubes 12AX7R.
I bought the Electro Harmonix tube as well as the Groove Tubes 12AX7R to compare. To my ears the Groove Tubes had less noise and I was able to get a louder and cleaner sound out of the amp, where the Electro Harmonix tube distorted quicker.
I believe I paid $15 for each of the Groove Tubes
Sounds great and I have been gigging heavily with the tubes in my bass amp for close to 2 years.
I also like that they are readily available at most guitar shops.
I can't think of any room or need for improvement. I like that there is a reasonably priced, decent sounding tube around.
So far so good. Two years of hard work on these tubes. Moving, weather changes and they keep in truckin'
My favorite tube out there for reliability and getting a loud and clean tone.
Lamp Russian origin team many Fender amps, including the Hot Rod Deluxe combo that I used basic test. It is a very good lamp, in addition, offers a great regularity in quality. Fortunately, one is tempted to say as Groove Tubes is a sorter! But it is never safe from a bad surprise ... This is not the case here and you can count on an excellent sort. This lamp sounds great. Its clear, it is balanced and does not put forward a specific frequency at the expense of another. It gives very sharp lens that can get a little annoying in "drive" mode, this time, a slight imbalance. But this is very tenuous. I like him, still in Groove Tube, the 12AX7C warmer and softer. But according to the sound is desired, it is always interesting to know that there are two AX7 in GT with a different sound character. This lamp can awaken a shy guitar in high frequencies or make it easier out of the mix alone.