I’m experiencing increasingly frequent instances where the power disconnects for a second or two and then comes back on.
The Directstream is on permanent standby and turns off, turns back on, reboots and stays on.
I’m concerned that this may be harmful to the DAC.
Can I use a UPS commonly used for computers just for the DAC without adversely affecting sound quality?
The power switch on the back just interrupts the AC and the DS has a transient voltage suppressor to protect it if there’s a spike when the power comes back one. So a power outage isn’t much different than turning the DAC off and back on with the back switch. I’ve done that to my DAC many times as much as any customer 
Conversely most UPSs generate crap waveforms, even the good ones use piece wise linear waveforms (read as lots of high frequency harmonics) not true sine waves so your DAC will probably sound different and most likely worst on anything that’s not a power regenerator style UPS.
Wow is Ted correct here. As in my home down south I have a large ups and it runs a bunch of stuff thoughout the home. Bad for audio . It adds a layer of haze for sure. I now use a couple of P10,s and it far better than a ups.
Al
For what it is worth, I use a PS audio premier but the DAC was totally fried by a direct lightning strike in my house anyway (audio board, bridge and two power supplies gone). I suspect it came in through the Ethernet the Synergistic Audio Tesla Cable more than anything else (otherwise I would expect the Premier to have died too). Or everywhere at the same time. Just want to caution that just a surge protector or UPS on the power is insufficient protection nowadays.
Did the ups indicate a strike ? It could be just as you state. . In my home down south I have a bunch of stuff to help but no direct connections is best . So audio is ona closed network .
Al
I live in a neighborhood which is about 35 years old, when new, the code allowed for the cabling from the power company to be installed under ground, without conduit. At about 28 years we had (seemingly) frequent power outages. I have a long-time friend whose husband is now a VP for a large construction firm, formerly a 1st class electrician. Before a major kitchen renovation four years ago, he came out and wired a nice whole house surge protector into our main panel (about $1200 at his price), and until our underground wiring was replaced (about 18 months ago), it would log as many as 122 surges in a month! Since the feeder lines were replaced (in conduit this time), we have seen only 2 surges in 18 months!
For my first audio system upgrade I added a Furman power conditioner behind an APC 1500 volt/amp UPS. I presume the power conditioner would take care of any “dirty” power created by the APC unit?