The receiver in question is an old Kenwood 1080VR that I'm using to amplify a stereo signal from a computer. When I first set it up the volume will be reasonably loud at "-40 dB" and loud at "-30 dB". But after months of time (6 months or so) I'm finding that I have to turn the volume up louder to get the same actual volume level. Now loud is around "-15 dB" or so. If I unplug the receiver and let it sit for a few days and then plug it back in the volume seems to be louder again and it's good for several more months. I don't think this is just my ear, it's getting quieter! Any idea what this could be? It's annoying. Thanks.