Here are the results of my testing scenarios
#1; Preamp connected to Amp via XLR (7 channels), Amp feeding speakers, amp on = no buzz, turn on preamp = no buzz. All else unplugged and unconnected (no power or HDMI cables, no subwoofer)
#2; Connect a HDMI cable to HDMI out #1 at 7005, EXTREMELY low buzz, I will rate it at .5 or 1/2.
#3; Connect above HDMI to HDMI in #1 at unplugged Plasma HDT, buzz a little more noticeable, I will rate it at “1”.
#4; Plug in plasma, buzz is heard, same as when plasma is not plugged in. I will rate it the same, a “1”.
#5; Attach cheater plug to TV and plug in, stays about a “1” and a crackle is heard every 5-8 seconds. Remove cheater plug.
#5; Attach both DirecTv RG6 lines to DVR, buzz stays a “1”. Plug in DVR, buzz remains a “1”.
#6; Disconnect the HDMI out from the 7005 and buzz goes back to a “.5”.
#7; Connect a HDMI in at number 3 on the back on the 7005, buzz is a tad louder, a “1”. Connect the HDMI at the DVR and the buzz is a tad louder, now at “1.5”.
#8; Disconnect the HDMI cable at both ends for the DVR (at the DVR and the input at the 7005) and disconnect the HDMI out on the 7005 and buzz is back at “.5”.
At this point the TV is still off but plugged in.
#9; Connect a HDMI to an output on the 7005 and to HDMI 1 on the plasma and the buzz is back at 1.
#10; Connect the HDMI from the PS3 (plugged in but not on) with no HDMI connected to the 7005 out, buzz is at “.5”. Connect the HDMI out at the 7005 and connected at the plasma and the buzz is back to a “1”.
#11; Connect the HDMI from my Oppo BDP-93 (not plugged in) and buzz is at “1”. Plugged in, it remains a “1”.
I also tried plugging the plasma into the same Tripp Lite Isobar using a thick 3 prong extension cord, and plugging it in to a different outlet/circuit, and neither helped.
Somewhere somehow there seems to be a ground loop occurring, and to me it seems like when I connect the HDMI to the TV to complete a connection between the 7005 and the TV, the ground loop is either started or exaggerated to the point where it is audible. The buzz rating of .5 is barely heard from 3 feet. Very tolerable if I was on my counch watching/listening to something. With the buzz rating of “1”, it can be heard at a distance of 12-13 feet, however it is very, very, low. When standing within 1 foot of the speaker it is quite noticeable.
I connected the other sources(PS3, DVD Jukebox, and the DirecTv DVR via HDMI and the buzz got up to about a “2”. This is easily heard, but not "loud" at 12 feet.
If I was to swap this AV7005 with my amp, and get the Marantz SR7005 instead, would I most likely encounter the same issue?Edited by cp1966 - 12/10/12 at 6:37am