Lohb
Headphoneus Supremus
Having the power attached will work, but it adds noise. Keeping it connected is only recommended for burning in cables, the amp, the headphones, etc. the adapter is really only for charging. It's a portable amp. You know.
I was looking to replace the noisier SMPS power block with a maybe quieter LPS.
It would save the battery, using it 50% in a desktop situation.