This is one bad boy tube! Highly recommended! I built an SE 6V6 for harp kinda based on the 47 Champ leaning towards a 5F2 without a tone control, and I won't divulge what rectifier, speaker or both xfmrs used and component value changes I've made. I have a retired mec engineer (hard to track down so that miser's 250,000 tubes stay stuck in storage) acquaintance and he gave me 2 NIB GE Black 6SJ7s and i put one in to see if it sounded better than my old and strong Ratheon Metal band, it did. Fast forward a few years--6 months ago--I told my buddy to nab one of these Red 5693's to upgrade the pentode for his cool Noble amp. Interestingly it didn't sound as good as the old glass sj7 in that Noble, and that glass didnt sound as good as the GEs in my SE, however, when i stuck the Red in my SE Growler...Sweet Mother Of Jesus! Bingo! For nasty amplified harp I'm a less is more guy in an amps circuitry and the tailoring of component values to get your amps tone dialed in is the road I go and that Red 5693 was the final nail in this amp. I was just asked to build something like my Growler but with about 20 watts.....boy do i wanna go SE with these Red 5693s in that build.