Blue Hawaii tube amp

If you want to ruin your amp, go ahead and use the KT77 tubes - NOT RECOMMENDED (you can verify this in the BHSE forum on HeadFi).

I’ve probably rolled 15 different types of EL34/6CA7 tubes in the BHSE, and found the vintage tubes to be very good - the older the better. Metal based sounded the best to me, than DD halos, followed by OO halos. If you don’t want to spend a lot of money, see if you can find a couple of used matched pairs of xf3 to get an idea of what the differences are between vintage and reissues. I don’t know if QC is better, but I wouldn’t suggest using Psvane tubes due to reliability issues (I never had a quad that last more than 1200 hrs).

You should really be asking this question on HeadFi, or reading through the BHSE thread on HeadFi if you haven’t already. I doubt you’ll get much help here.

http://www.tubeaudiostore.com/elpremgrad.html - " The Siemens EL34 is one of the best EL34s made. These tubes are rare, new old stock tubes made with East German precision at the original East German factory, so basically Telefunken". These are black based tubes, not brown based like the ones on the bottom left in the link below. The rest of the tubes from Telefunken " EL34 tubes made by Telefunken in West Germany are pretty rare and Siemens and Lorenz never made any EL34 tube.

Take a look at the bottom of the page on the right hand side from the link below. Read the comments for the other tubes as well - http://www.tube-classics.de/TC/Tubes/SieTel%20EL34/EL34.htm

No way I’d pay $500 for a quad of those. I had 2 quads of the Siemens RFT tubes (East Germany) and never liked either of them. You could probably find mint NOS Mullard xf4 for the same price if you look hard enough.
Link to Philips/Mullard -  http://www.tube-classics.de/TC/Tubes/Valvo%20EL34/EL34.htm