More about that Chinese amp

Well, I peeked inside the amp and took off the transformer covers. There are indeed 3 transformers. From what folks have said I half expected to find some sort of weights under the xmfr covers because the amp is so heavy. Nope, just copper and iron. Inside the amp are no solid state devices but for the Bluetooth module, which connects to the input through a relay. So the amp switches automatically between inputs depending on whether the Bluetooth module is recieving a signal. On to the tubes. I turned the amp on again last night and just listened. After a while, maybe 45 minutes, I heard a crackle. Looking carefully at the tubes I noticed that one of the EL34 tubes was glowing brighter at the top than the other EL34 tube. There is a mica disc in the top of the tube and a little of the filament protrudes through a small hole in the mica. And this is what was glowing brighter. I tapped the tube and heard the noise coming out of just the left speaker. Tapping the right side tube produced no noise. I though that maybe one tube was getting more voltage than the other so I waited for things to cool down and then swapped tubes. The same tube got brighter but was now on the right side. So the tube must be bad because the problem travels with the tube and the same tube gets brighter no matter which side it is plugged into. So, anybody have suggestions on tubes? I'm not an audiophile. My hearing isn't good enough. I don't think matched pair tubes would make any difference to me ears. But I can hear well enough so a fairly high quality tube set would be desirable. And I do think I should get a pair so that they will hopefully last tghe same amount of time. Thanks, Eric