Update: The Furutech tp-609 passive power distribution unit AND the Equi=Core 1800 balanced power conditioner are BOTH hum free!!
This confirms some sort of mismatch in power or grounding between the Puritan PSM156 and the Backert Labs Rhythm 1.4 preamp.
So if I elect to keep the preamp, I will need to invest in another power conditioner for the main system here… maybe a new thread for that… Unless anyone has a good recommendation for something at least relatively close to the $2300 price of the Puritan, but some more $$ is fine to consider. The Puritan is so good at its price, I’m worried what it’ll take to match its performance.