I have done more digging and I think the issue is with the power brick itself.

I was using the speakers outside on the deck plugged into the outside wall socket. I had the speakers on stands and really didn't take the time to route all the cables.

I put them inside the front sitting room to do some more testing and noticed the power cord doesn't fit in very securely into the power brick. Outside this I think was more or less dangling as the height of the outdoor stands are pretty tall compared to indoor stands. As well, the size of the actual power prongs in the brick are smaller than standard. It sort of reminds me of an old amp that I had that required a special C13 plug for it to work. Any North American computer plug (C13) just wouldn't fit and was too loose and the stereo had problems.

I just for giggles took a power meter to the 15v barrel plug end to give it a test and was getting readings all over the map under voltage. I think that if the power going in isn't right then how can you expect the rest to work. I did hunt high and low to see if I could find that special C13 power cord but I didn't.

I did, however, get through to Axiom and was hoping that they could send me a replacement power brick assuming that there might be something really wrong with the one that I have, but after speaking with Deb, was told that Andrew wanted the whole set of speakers sent back. Can't understand why as the one on the left doesn't have an amp or any electronics inside of it, so I would have thought for testing they could have just had the one on the right with the USB/Amp inside. But they wanted everything so off it went this afternoon.

I didn't get around to testing the speakers hooking up to my new Raspberry Pi3b+ running Volumio. I think that is likely the way I am going to be playing mostly. That way any guest can just log onto the Volumio.local web page and call up other songs that they would like to hear.

For the part mixers, I think it might be better off to use the 3.5mm headphone jack to connect off the back of the mixer than route everything back to the PC and then USB connect to the speakers. Again, that is another setup that I have not given a try to.

Anthem: AVM60
Axiom: ADA1000, LFR1100, VP180, QS8, EP500, M3, M3comp
AudioSource: Amp One/A