@invalid thank you for the pointer to Space-Tech Lab. I hadn't heard of them before.
@russ69 can you elaborate on what you mean about the preamp? My signal path now is turntable-external phono stage-preamp-amp. The preamp is operating in 'direct' mode, which provides no gain or tone controls. It's essentially merely an attenuator. What about a preamp makes it "key to a good system"? It seems like replacing my preamp with an attenuator would be an even swap in terms of the signal path.