On Tuesday, I became the proud owner of an Amp Ultra. I love everything about it. It plays beautifully with a KEF Q350. But there are two things that make me unsure. First, the top of the enclosure is very warm. Warmer than the first WiiM amp. Maybe that's normal. But today, I put my ear to the enclosure, and I could hear a squealing and grinding noise inside. I need to listen more closely, but all the sounds are still there. In standby mode, it's silent. I'd like to ask other owners to listen and tell me if they experience this squealing noise, and if it's even supposed to be there, or should it be quiet inside the enclosure?