Thanks Perry, Great info - I see some I'm going to get. I think it's any 10 that are on sale. I believe you are referring to www.abcvacuumtubes.com, right. I use 12 volt tubes in place of the 3tf7 and they have one of them on sale, 12ct8. I believe the alternatives are: 12bh7, 12by7, 12ct8, 12dq7, 12bv7 and maybe 12fx8. Regards, Larry