OpenTheremin V4 audio out directly to headphones OK?

Hello Folks!

I have an OpenTheremin V4, and I want to make a very simple and compact practice setup for silent practice—meaning to headphones.
I have it running through a small mixer (Yamaha MG06) and it works, but I want to go more simple.

I am getting some conflicting information on the internet. I believe we shouldn't plug headphone directly into the audio out of the OpenTheremin?
Someone, however, instructed that you could/should.
My knowledge of electronics/audio is at a novice level so please forgive me for any ignorant questions!

Any guidance would be much appreciated! Thank you.

Late answer, sorry ...

If you connect your headphones directly to the OT V4 you will face these 3 problems :

TRS jack carries 2 signals, tip is the audio output and ring is gate signal. Then one hear will hear audio, the other will hear noise glitches. but let's admit you can separate them through proper connectics. 

Then comes the 2nd problem, the audio signal will have 5v pp amplitude without maximum volume control. Which may be a bit loud for your hears. 

And probably headphones' low impedance (typ. 32ohm, 16 ohm if they are parallelyzed) may overload output circuit (not so sure for this last one) 

That's why it is advised to use a small headphones amp with volume control. 

Late answer, sorry ...If you connect your headphones directly to the OT V4 you will face these 3 problems :TRS jack carries 2 signals, tip is the audio output and ring is gate signal. Then one hear will hear audio, the other will hear noise glitches. but let's admit you can separate them through proper connectics. Then comes the 2nd problem, the audio signal will have 5v pp amplitude without maximum volume control. Which may be a bit loud for your hears. And probably headphones' low impedance (typ. 32ohm, 16 ohm if they are parallelyzed) may overload output circuit (not so sure for this last one) That's why it is advised to use a small headphones amp with volume control.

No need to apologize! Thank you for your thoughtful answer. It is technical enough but easy enough for me to understand!
I shall continue to use the small mixer as it works well.

Many thanks again.