I hate to say it, but I think that's just a fact of life with the Crown XLS. Many of us use them for subs where such issues aren't really a concern. I have an XLS 1502 powering a sub but I never considered using it full range. It definitely gave me a hum, so I put a low pass on it with a miniDSP which pretty much took care of it--something you can't do if running it full range.\n\n\nI've had a Crown XLS running my subs for years. Never had any sort of hum.