My new Princeton Reverb RI Amp started making a static noise on start-up just several weeks after purchase. Rather than trouble shoot which tube was suspect, I replaced the entire set of factory tubes with this Premium Package. The noise went away as expected. But, unexpectedly, the sound of these tubes in my amp is SO MUCH better then the originals (when they were functioning properly). Vast improvement in tone!!! Well worth the money and I feel confident you will be impressed with the results too.