stevem2 said Good to hear, except the last bit. It's always something.The nice thing about the BHK preamp is the headphone jack. That let me determine if the problem was in the amp or the pre. Turns out everything sounded fine on the headphones for about an hour, so that wasn't the problem. So I cleaned the tube socket contacts, and that seemed to clear things up. The system has been running fine for about 2 hours, so that was most likely the problem. (I had used some tube contact cleaner and protectant before word got out not to use it for this very reason, so there may have been some residual protection goo that affected throughput a bit.)
Anyway, I’m all good.