I have an LFM-1 and 1050, and in really hot weather I get a loud hum coming from the subwoofer. If I turn that off, I still hear the hum in the speakers. Again, this only happens in hot weather, and it doesn't seem to be any particular component causing it as I've tried the old "unplug everything until you find the source" trick. It tends to happen even if my AC is off, so I'm thinking it's something with my refrigerator, but I could be way off.

Any ideas?

Have you got cable or satellite television, with a coax cable coming in from outside connected a 'box' that is connected by more cables to the rest of your gear? Powering down or unplugging the power cord to the 'box' won't be enough, if the problem is coming from there. To check this, you'd need to either power down the 'box' and disconnect the incoming coax, or power down the 'box' and unplug the power cable and all other cables that link the 'box' to your system - in other words, total isolation from the coax coming in from the outside including no 'box-to-other-gear' case contact.

If the external coax connection is the culprit - and I think it is more than any other single cause, there are isolators that can be installed.

Another possibility that ties into the hot weather is the electrical grid itself: if the overall load on the grid is too high (due to all of your neighbors running their air conditioners) you may be experiencing just enough voltage dip to upset certain electronics. Again, this is just a guess on my part, and I'm not sure how much dip would be required to make this explanation plausible.

Thanks for the feedback. I actually don't have cable hooked up at that TV, so that's not it. As for your theory gonk, I wonder if using a UPS would even things out enough to compensate. I have a spare one around, so I might try that. Couldn't hurt any.

I don't know if a UPS would help or not (depends on how the unit works when power is available), but as you say, it couldn't hurt.

Well, now I have to wait for the hum again. It was hotter today than yesterday, but no hum. I'll try the UPS the next time I get a hum, but the fact that it's so hit or miss makes it hard to troubleshoot.