Please answer all the questions, if i shall have a chance to help you troubleshoot. It's very important to know, if a single CPU core is overloaded. Please keep in mind, that a overload of a single core does'nt shoow in the total CPU usage meter.
Which CPU do you use? Full name please.
Which driver are you using for your Helix and why is the buffer set to 480 and not ie 512 samples?
I understand the soundcard is integrated in the Helix board.
Are you sure there is'nt any input or output that is over 0db?
Is the preset you mention the only one, where you have this issues? It would be easier to check, if you could mention a factory preset to check out.
What's the Playmode setting for the preset? Full name.
Do you have a MPE controller?