I have a Denon AVR-X2400H receiver. I've recently noticed a sort of popping (clicking?) noise when adjusting the volume using either my phone or the remote. The noise is proportional to the volume that the receiver is at (higher volume on receiver = louder "pop"). The sound is coming from the speakers and subwoofer, not the receiver itself. Is this normal behavior or is there something wrong with my unit? I didn't notice it when I first got the receiver, which was only a couple of months ago. If this is an issue, does it seem like something that would be covered by the warranty? I have emailed Denon, but I figured I would try to get some info while I wait for a response. I tried calling, but the wait time was too long. Any ideas on how to troubleshoot the issue or who to contact would be appreciated. Thanks!