I run Amity labs power supplies on my L3's and S9's. This unit powers 2 S9's, very good quality! https://www.ebay.com/itm/Power-Supply-for-Two-x2-Antminer-S9-S7-L3-with-Ready-To-Plug-Harness-/182254895754
+1 to Amity labs PSUs. I have 1 and absolutely love it. If I didn't already have 4 apw3++, I would buy another Amity Labs. Great quality. I even picked up their PDU that runs off of my dryer connection, allowing me to run 4 S9's on 1 220v connection until i have my shed built to run everything.
Do you have a link for the PDU? I have an immersion experiment in the works and would LOVE a unit to power all four S7's!!!