Just curious, How do you connect your minijack headphones to the Devialet output?
You will need to do a bit of re-configuration.
You need to use coax 1 and coax 2 re-configured as a pre-amp output.
You will need either a hybrid 2 x RCA to headphone socket cable or (as I have done) use a 2 x RCA socket to headphone socket adapter which I got from a local electronics supply store for AU$8, then use your own cables.
You also need to re-configure your remote so that the balance/tone/SAM button becomes a pre-out on/off button and don't forget to disable "mute" on the pre-out.
Then, when you want to listen to headphones, just switch on the pre-out and mute the speakers.
The downside to this is that you lose the balance/tone/SAM functionality unless you use a seperate SD card for those times that you want to use headphones.
Hope this helps.