So I decided a create a living room setup with my lesser used gear and noticed the Atom can cause issues when the DAC feeding it is split to two amps. When the Atom is off, it can cause an audible high pitch ringing on the other amp. When it’s on, there doesn’t seem be an issue. It’s really obvious if your playing a test tone. Anyway so that’s something to watch out for if your splitting a DAC output.
The entire time I had my atom as my main amp I did this (split the output from my modi 3 to my atom and my powered speakers), but I kept the atom on at all times so never experienced it. You could always just turn the volume all the way down on the atom without turning it off. It’s a very cool-running amp, so no big deal leaving it on.