@Pasha makes an excellent point. I followed up by reading some articles and, even the APC units I relied on don’t seem to be good options. Perhaps, the AudioQuest PowerQuest 2 or Furman PL-8C would solve the ground contamination problem. They cost substantially more (around $300), but are on the lower end of the price range for power conditioners.
Surely, we have other experts here with advice. Too bad the companies that market DJ equipment don’t offer advice and partnerships. Of course, in the deluge of information, maybe it is offered and we overlook it.