No, unfortunately this is not possible. The alarm tone sounds at the programmed alarm time. 20-40 minutes before the set alarm time, the alarm clock switches on its built-in LED. I have set it for 20 minutes and I usually get up before the alarm tone starts. I then switch off the alarm and the light. You get used to waking up with the light on, which is really pleasant.

With the HF3520 model, both the volume and the light intensity can be set to "Off".

Well, with mine you can set both the brightness and the volume per alarm time in the menu, and OFF is possible.