Since you can hear the noise through your speakers when you tap on the knob, that is a microphonics issue. They may still be fine for another application, but not in a high gain preamp. The feedback is likely a separate issue.
I clicked on the link in the video FRM posted and it took me to Brent's website. Perhaps he didn't test these tubes as well as he could have. I'd exchange them explaining the issue. You'll likely get a better pair if they're available, or a refund if not.
It can be hard to get a hold of Andy sometimes. One man shop. Sometimes he may not have what you need on hand but he has sources and is always buying tubes. I let him know what I need and he usually calls back to say he's found/bought some.
Once you hear the tubes that bring the magic, it can be hard to even turn on your stereo until you have them.
