Unless someone owns the same preamp, recommendations may help, but a different circuit will result in different sound.
I had a preamp that used 12au7 that was meant to stay on 24/7, it has been so long, I can't remember what I was running. But those tubes, in that circuit lasted for years.
I mostly wanted to comment on CJ, the preamps that run 6H30s, I have one a CT5, are easy on these tubes, I just replaced the tubes for the second time, after +7000 hours, and if they had deteriorated, it was so slight as I could not swear to it. The 6H30 is one of those tubes that there are only 3 options. NOS, hard to find, and if you do, a minimum of $250 for a pair, if lucky. The EH gold pins from Cyroset run me about $90, shipping included. I found about 75 hours to settle in. They get a little bright around 50hrs, then by about 75 hrs, they are done.
I used to have a preamp, that used 6CG7/6FQ7, that I rolled at least 10 different tubes through. At that time, almost everyone recommended RCA Cleartops, I found the RCA Blackplates, Toshibas, and the winner to be Mazda. If you can find someone with the same preamp, their advice will be most helpful.
Maybe I am a minority, but after a lot of rolling in two different preamps, I got tired of it. I prefer to listen to music, not tubes. My CT5 makes that easy. No fretting over is there a better choice.
I had a preamp that used 12au7 that was meant to stay on 24/7, it has been so long, I can't remember what I was running. But those tubes, in that circuit lasted for years.
I mostly wanted to comment on CJ, the preamps that run 6H30s, I have one a CT5, are easy on these tubes, I just replaced the tubes for the second time, after +7000 hours, and if they had deteriorated, it was so slight as I could not swear to it. The 6H30 is one of those tubes that there are only 3 options. NOS, hard to find, and if you do, a minimum of $250 for a pair, if lucky. The EH gold pins from Cyroset run me about $90, shipping included. I found about 75 hours to settle in. They get a little bright around 50hrs, then by about 75 hrs, they are done.
I used to have a preamp, that used 6CG7/6FQ7, that I rolled at least 10 different tubes through. At that time, almost everyone recommended RCA Cleartops, I found the RCA Blackplates, Toshibas, and the winner to be Mazda. If you can find someone with the same preamp, their advice will be most helpful.
Maybe I am a minority, but after a lot of rolling in two different preamps, I got tired of it. I prefer to listen to music, not tubes. My CT5 makes that easy. No fretting over is there a better choice.