There is no way for me to tell, I've not tried the unit and have no experience. They quote 4.2V balanced and 2.1V single ended with "no load." If they could hold that voltage with a 12 ohm load there'd be more power than you could ever use, but that is an entirely useless spec as load can vary from 8 to 600 ohms with ear gear and if the amp has weak current output they may not ever be able to reach those voltages. An owner would have to answer that subjectively.
I've found measurement in the site below.
It's not my site, but he is measuring output voltage by ohms.
You can see it dropping significantly when the impedance go down.
Read from the graph, at 12ohms, apparently less than 2Vpp which means less than 0.7Vrms.
This is typical A&K DAP characteristics. (the site has a lot of measurements for other models.)
Review site (in Japanese, not mine):
From above site (not mine): Measurement graph of SP1000m (Impedance - Vpp)
(Vpp / 2 / 1.44 = Vrms)