I must retract all of the erroneous comments about that power supply. I didn't look carefully enough at that PS schematic and thought it was something else. My bad.
ACnotDC in post #419 is correct about tying the two PS grounds together, because there is a high current path between those grounds.
ItsAllInMyHead you should connect the ground wires to the ZD25-Mini PCBs to the same PS GND point to form a star ground. The image in post #407 shows one ground on the PS+ GND side, and the other on the PS- GND side. Continue to have one ZD25-Min i PCB with a ground loop breaker.
Not a worry. For all intents and purposes, those two connection points are "the same". You are correct that one channel's GND was connected to the + rail side of the PSU and one to the - rail side of the PSU. However, they did have a jumper between to "make" it a bipolar supply with a common GND.
I'm never embarrassed to share mistakes in the hopes that someone reading may not replicate my error ... OK, I'm a little embarrassed.
I took out the PSU yesterday just after William's post. I added additional jumpers between the GND points from the "+" rail side to the "-" rail side of the PSU board per everyone's kind suggestions. I thought it would be also be a wonderful time to redo the layout a little to add some physical space between the DC wiring and the PEM.
Well .... I have now joined the "You can't fix stupid" club.
My intention was to "go vertical" and move the PSU board toward the front of the chassis. It was mounted on threaded rods to raise it over the toroid. I've mounted things similarly before with another PSU. I put a set of cap boards over the inductors/chokes in a "CLC".
I was in a hurry (stupid) and didn't check the clearances. My K-lock nut on the underside of the board was large enough to overlap slightly with one (or both) of the supply traces/pours. Additionally, I had tightened it enough to where it cut through the solder mask and shorted one of the rails to chassis GND through my mounting rod.
I typically have these boards mounted with nylon spacers.
I was
at my boneheadedness and decided to leave it alone for the rest of the day.
Thankfully, I was at least smart enough to re-check the PSU with a variable transformer before re-connecting the amp boards. I didn't however have it on a DBT and wasn't using a 0A5 fuse per my normal process. It was at about 40VAC at the primaries when it when poof. So, at the moment, I am trying to figure out which component(s) released that little puff of smoke. Troubleshooting is not my strong suit...
So, if anyone has a tip for boneheads, I'm all ears. I had mentioned wanted to use a different PSU anyway.
So, I'm putting together another PSU in the interim, until I decide what to use permanently.
Moral of the story... don't be a doofus like me.