I have dedicated lines, but why is this happening?

TWL's answer makes the most sense. I sometimes get a pop from the microwave. It's RF and it somehow gets in my system. Maybe shielding the RF source will work.

Maybe the AC's relay contacts are fried, and it's easily replaceable? Nothing like really dirty contact sparking to mess up your minigrid, eh?

Thanks for all of your replies.

The dedicated lines do not share neutral lines. I helped the electrician pull and install the lines.

I don't believe the problem could be a result of corroded or loose wiring as we just built the house a year ago so everything is new. But then again, it would be worth checking.

Albertporter, I will definitely check out your suggestion. It certainly makes more sense to keep something out rather than trying to get rid of it later.

Sean, the only changes I have made in recent months were to change the caps in my amp as you know and I then added interstage transformers to my Audio Note DAC. Nothing else other than isolation platforms and DH cones. So I don't think a component change is the problem. But I do think the suggestion to clean the grounding rod is a good idea. I hadn't thought of that and that could help.

I have also been considering installing balanced power transformers on my dedicated lines ala Jon Risch. Would this eliminate the problem?

Thanks,

Warren

One more question regarding Warrenh's post about a dedicated ground.

Sean, I searched your posts on isolated grounds here and I am still not sure I understand it.

When we installed my dedicated lines we used 12ga. Romex and 20 amp breakers. We ran each leg in conduit with the conduit tied to the breaker box, but with the conduit stopping short of the outlet boxes (plastic). The ground in the Romex is connected from the Acme outlets to the panel.

The only thing plugged into the outlets are my audio equipment since they are located under the house. I had a hole cut in the hardwood floor behind my equipment rack and ran all power cords out of sight through the floor to the outlets beneath.

How do I change this to make it an isolated ground?

An additional suggestion: try measuring the AC voltage at the receptacle before and during the moment the A/C system is energized. Buy a plug-in AC voltage meter from Radio Shack. At the instant the A/C system activates, the high starting current of the compressor may momentarily drop the AC voltage at your stereo to 100 VAC or even less. If your gear already draws significant current, or your entire neighborhood is blasting their A/C systems, or you have the whole house lit up, the voltage may already be dipped. If the additional voltage dip is low enough, one or all of the pieces in your system may be generating the pop noise.