Amplifier used w/ headphones and no speakers connected, can it be damaged?

I use an Audio Research REF75 SE with a speaker tao to headphone adapter with my Abyss 12266 TC with no issues. I asked AR technical support before I bought the amp and they said there would be no problem with the amp. They were more concerned with my ears.

I had seen other people on the Abyss forum use speaker amps fpr thei TC and so I wanted to give it a try. I first used a Simaudio 600i V2, and then decided to try the AR amp. iI sounds great and there is no hum or noise through the headphones.

I did have the WA5 many years ago.