Balanced Audio Technology MK-30 tubes. Alternative to Sovtek 6922

Ting each tube with a pencil tip and see if it's sensitive to the taps. You might get away just replacing that one. 

I think you mean a "VK-30" and not an "MK."

Tubes are graded better when they are lower noise and more closely matched. It sounds like you only need lower noise.

I would call Kevin, Brent Jessee and Jim McShane and explain your problem. I think any of those three will be honest about whether they have tubes that will solve your problem, within your budget.  If they don't, sell the preamp.

First off I’d give BAT support a call. I’ve had several BAT amps. all are balanced and spurrious noises are routinely absent. I rolled tubes in an older vk5 pre and in a vk60. noise was never a consideration while interjecting different tubes. consequently I feel the issue is elsewhere…. more than likely.

however the tube replacement options are immense. 6DJ8, 6922, OR 7308 ARE PLUG AND PLAY REPLACEMENTS.

to verify the issue is in fact tube related merely buy any actually ‘new’ ones regardless brand and plug ‘em in. I should think BAT offers something here too, but finding something kshould not be difficult.

BAT amps are all self biasing so even if the what ever tubes are not new for example, things ought to reveal if a tube issue or not.

and I’d call BAT about this anyhow. hopefully it is merely a poor tube.

the flip side of the coin does seem to obligate the seller to explain their notice of ‘clean and clear’ IMO. Very good luck to you..

I will say on the subject of Gold Lion 6922's I retubed my preamp with them and found them to be too bright. I love the Gold Lion KT77 but with the 6922's I ended up taking one pair out.  My preamp uses 6 tubes, I rolled in a pair of Matsushita 7dj8's in first position and ran with that and 4 Gold Lions and it was perfect. As always YMMV.