Battery-Powered Audio System Buzzing?

Thanks to everyone for the input. I confirmed that my Anker battery creates a pure sine wave. It also has a maximum output of 1800 W, and my system on average draws about 175 W. @erik_squires thanks for the suggestion, I had not put everything in the system on the battery. Once I did the buzz basically went away. Thanks again!

@immatthewj I am trying this setup with both my upstairs and downstairs systems, the difference being the downstairs setup has the Schiit Aegir going into Tekton Impact monitors. For the downstairs setup, yes it is a dramatic improvement. The sounds was great to begin with, but on battery there is a wider soundstage, more holographic presentation and for lack of a more clinical term - an intoxicating musicality. On the upstairs system with the Tyrs and the Encore towers the difference is harder to tell. Now that I have it setup on battery I will try A-B ing between battery and wall-power to listen more critically for differences. 

While I appreciate the other suggestions, this experiment is already into as deep technical waters as I feel comfortable wading through.

And yes, originally when I posted I still had 2 subs and the DAC going through wall power. Once I put everything on the battery the buzz disappeared.

@immatthewj After A/B-ing with the upstairs system (Schiit Tyrs/Tekton Encores) I've come to the conclusion that while there is a difference between battery and wall power, it is very slight. One is not better than the other. Not worth the annoyance of dealing with the batteries. I will A/B more extensively with the downstairs system (Schiit Aegir/Tekton Impacts) and report back. It was on that system that I originally noticed the big difference I described above. We'll see if that holds under more scrutiny.

@goldenways I definitely don't want to harm my equipment. I'll reach out to the manufacturers of all my gear and see what they think about powering their stuff with batteries.

An update for any who are interested - I heard back from all the manufacturers of my gear.

- Don Sachs said no concerns for the preamp. It draws at most 150 W. Only issue would be if voltage drops. "You won't hurt the preamp. The preamp will run on 100 volts, but the regulated supplies will not regulate and it will not sound good.  As long as it sees 113 volts or more then it is fine."

- Schiit said that in theory their gear should work without issue to use battery power, as long as the batteries are supplying the recommended power. But they can't officially endorse it.

- Rythmik said "Keep the voltage within spec. For instance, 120V 60hz is better than 120V 50hz for the transformer." 

So my takeaway is that with a quality battery that provides appropriate power, there is no concern about using it to power audio gear.

Additional update: My basement system indeed does sound better on battery power. However, since my Yggdrasil OG DAC remains powered on all the time, the nervosa of constantly watching and recharging the continually draining batteries got to be overly annoying and not worth it to me. I'm now back to wall power both up and down.

@erik_squires That's a great question. I don't watch my incoming house power. I'm not sure how to do so, but that would be interesting to learn.