I have the LTA MZ3 and I leave the PSU on all the time. It does not put out any heat when the MZ3 is not being used. I believe the manual says it can be left on as well. My Benchmark DAC does not have an on/off switch and it is left on all the time also. It puts out a decent amount of heat for it’s size but as far as I know, it was designed to be left on.
Al
Al