6H30 tubes ringing in BAT VK-300SE

I have had this issue in nearly every 6H30 tube I have bought for my BAT VK-300xSE integrated. Whenever I switch inputs, or the unit comes out of warm-up mode, or out of mute, I get a high pitched ping followed by a ringing sound out of the speakers.

I have tried 3 different sets of tubes- two pairs of Electro Harmonix gold pins, and one set of Sovteks. Eventually it gets to the point where if I tap on the chassis of the BAT, I get the high pitched ping/ringing out of the speakers. The last new set of EH's I bought, when I pulled them out of the box brand new, and tapped on the side of them with my finger, bingo- it audibly rings in my hand!

It doesn't seem to affect the sound, but none the less, are there any good sources for QUALITY 6H30 tubes? I am not going to pay $300-$400 for a pair of the "New old Stock" DR tubes. I have bought all of the Sovteks and EH's from Music Direct. Maybe they got a whole batch of bad ones?

Please Help!!!