Last night, I found that I was getting a minor hum coming from the phono connection on my Denon AVR-2105. At first, I thought it was a splice to the grounding wire (the wire would not reach), so I started to troubleshoot by disconnecting it from the Denon. Note that both the Denon and the turntable is turned off (well, the Denon was in ‘standby’). When I turned the Denon back on, I was surprised to find a much louder hum. Next, I hooked-up an outboard phono pre-amp, undid the splice and ran the grounding to the pre-amp, and went in one of the 2105’s line-level inputs. I had done this for years on my old Marantz SR580 (no phono input) with no trouble. I got the same results (small hum with grounding wire hooked up, loud when disconnected). In all cases, the turntable itself was off, and was not sending any signal. How does the 2105 know whether the grounding wire is connected in this case (if the turntable is off)? I can understand when using the phono input (the amp knows that a ground should be hooked up?), but when using the outboard pre-amp and coming in one of the other inputs, the 2105 should not be able to tell, right? I mean, the phono pre-amp just boosts the phono to line-level (same as any other line-level source), right? Finally, do any of the experts out there have any suggestions as to how to eliminate the soft hum? Thanx!