Hi, I have a DDA-100 which I bought in January which also has a faint whirring sound when no music is playing and which can be heard when you have your ear close to the unit. It sounds a bit like a hard disk. I returned the unit for repair but I still hear the noise so am considering returning for a replacement. The problem is the shop I bought it from where I live in Stockholm, Sweden, has no more units in stock. My unit's number 0406143. How did you go forward with your issue?