Has anyone tried going 13 volts on their external power supply to DAC+? I read that this improves the sound greatly, so I tried it and it did. I switched back to 12v since I'm worried about toasting the unit. Anyone know if 13v is safe? I emailed Mytek and it's no surprise they said run 12v. Knowing all to well about liability, even if it can do 13v, they won't recommend it since that's not what is published in their manual.