I wondered about DC offset, but to me the difference in the +ve and -ve cycles looks too pronounced.

I may just have to live with "it sounds OK" until I've saved up for a 910!

I've just noticed a new recent firmware release for the 3K http://music.yamaha.com/products/downloads.html;jsessionid=05DEBA11BCA961B65CC8C75AE41697B8?productId=106898

I don't really see what difference it would make; I don't need the new functionality but is this worth a go just to see?