I'm brand new to the world of tube audio amplifiers although it's fast becoming an obsessive hobby. The sound improvement over the stock tubes is astonishing. There's great stereo separation, a much wider soundstage, crispness and detail in the instruments/vocals and punch in the bass/percussion. And talk about headroom - I've never needed or wanted to go past the 11 o'clock position on the volume knob (driving a pair of Klipsch RM-15s and a small subwoofer in a medium sized room with vaulted ceiling). I've run these tubes about 30 hours over 4 days and they seem to be getting better and better with each use. Highly recommend this upgrade package.

Great upgrade, bass response, clarity, headroom and separation all much better. Running Klipsch Rp-500m bookshelf speakers. Plenty loud at 30% volume, no distortion at 100% but too loud to listen for longer than a few seconds. 100% satisfaction.

The tubes are fantastic, am able to hear every instrument in our Latin music. Very warm, and clear. Strongly recommend and the folks at the TubeStore are super knowledgeable and friendly.

My old NAD died and I haven't built my Transcendent kits yet so I grabbed this Monoprice Pure Tube amp to tide me over. Well, from the factory this little amp had a 50 db (50! Measured with 2 different meters. Holy cow. ) 60hz hum from both channels at zero gain. Absolutely brutal. Swapped the tubes for the premium package and zero hum from the right and a tiny bit from the left before burn in. To say the difference is night and day would be understating it. Easily runs my Klipschorns at impressive volumes. And overnight service on Dec 23 for $13 bucks! That was sweet. Good job Tube Store. You'll be hearing from me when it's time to tube up my kits (25 tubes. Whew. )