The heat dissipation is solely done by convection (there is no ventilation in the Devialet), we advise not to have the unit in a cabinet or in a place with poor air circulation.
You can check the Devialet’s temperature by pressing 2s on the remote tone button and going to screen 14th ont the Devialet’s information screen. You can navigate the screens by shortly pressing on the tone button. Temperatures going up to 65°C are absolutely OK.
Additionally for DUAL-Mono setup, we highly recommend you to set device side by side rather than one on top of the other one.