ZeosPanteraPatreon sub here, how do believe a set of TH-X whatever's would pair with this bad boy? Picked up some EM-U Ebony's a couple weeks back and would be interested to get into a tube situation with them and maybe some 598's. IYO yay or nay?
PixlatedOn the cheap try a GE 6080 for the output (the bigger tube marked 6AS7 on the plate), that's where I started. So far it brought the biggest improvement over stock. For the driver tube Sylvania 6SN7 chrome-top is a safe inexpensive choice, it brought additional refinement in my case. There is an epic Darkvoice tube rolling thread on head-fi, lots of good info there.
PixlatedAnother suggestion for the output tube is Russian 6N5S or maybe the later 6N13S variant, about $15 shipped from Eastern Europe, lots of NOS available. I got one recently and like it, very open sound with good treble and bass extension. Similar construction to the big stock tube but sonically night and day.
PixlatedIf you're on a budget, if suggest the RCA 6as7 with black plates for the output tube they're cheap at around $15 for NOS and a 1952 Sylvania 6sn7gt "bad boy" tube which runs for about $45 used. If you have some extra money get the tung sol 5998, GEC 6as7g, or Western Electric 421A for the output and a tung-sol 6sn7 with round plates or the Sylvania 6sn7w with the metal base.
g_v_lSorry to hear that your tube is humming. Hopefully the burn in period will fix that! If you're using the Dark Voice, look into the Fitz mod to fix the humming issue for all tubes.
SmokujinLooks like the tube is a dud, marginal for pre-amp duty but has no power to drive my phones and is badly out of balance. So much for the "NIB", trying to arrange a return.
g_v_lReturned the bad RCA tubes to the seller, sounds like he had no clue they were used and end of life already, I'm on my second 6AS7 RCA pair from the WWII era. They sound really nice in my system, finally the sound I was trying to find. One is a JAN (military) and the other is the normal consumer variant, slightly different design, similar sound signature, I like the JAN one better, sounds richer with deeper bass, out of the box with no burn-in anyway.