I suggest you check with the designer of your amp, and see if you can substitute other tubes in place of the KT88. Possible alternatives (beyond the KT90 already suggested) are, 6550, 5881, and 6L6. Old stock American tubes (used, good) are superb, such as the Tung Sol 6550 and 5881. Many designs that use KT88 can use these tubes. Old stock American tubes can often be found at Antique Electronics in Arizona. The comments about the Genelex Gold Lion are absolutely correct, but they will be (probably) over $150.00 each tube, maybe much more. Good used US Military 5881 show in Antiques catalog at only $17.00. If you must only use KT88, listen to the Tesla KT88, or even the Svetlana 6550, I think that both of these are better than the Sovtec.
