Originally Posted by quack724
Thanks very much for the suggestions Ray. I actually had hum with the Onkyo too. I wrote a post on this issue
in 2012 but did not get replies. You are the first to comment
Things I've tried since my 2012 post
1) Jensen isolation transformer but it did not help.
2) Isolating the power cords to one side of the rack but the Odyssey amp has it's power cord sticking out back from the middle so it's hard to prevent the Odyssey from not being near the non power cables. My Odyssey is 2nd to bottom shelf. I might try to place it on bottom shelf to see if having it's power cord even further away helps.
3) For whatever reason, there was a time when I used RCAs for the Odyssey L&R channels (instead of XLR like I do with my Sunfire 5 ch), the hum would go away and be stable but when I re-insert XLR to L&R *or* put back the same RCA cables I would get the hum again. So I can't consistently reproduce the issue or workaround.
4) Remove all other components except Marantz, Surge X, Odyssey . Odyssey to L&R speakers alone (no Marantz) = no hum.
I will look into your ground suggestion.
I will try to help with some of my basic knowledge.
I would make a new thread into the speaker or AVR/pre-pro, this would get you a lot more traffic and some with more knowledge will reply.
Pm me so I know where to look!
It sound like your Hum is only from your main and not your surrounds or center.
Also you use "Jensen isolation transformer ".
So I will go with the obvious.
pre-amp, amp and speaker cable.
I do not think it is the pre-amp (or the patch cord for signal since you tried, RCA and XLR) since you had switch between two of them, but let's make sure.
Did you try to change the patch cord from the main and switching them for the surround?
If the Hum move to the surround instead of the main, the pre-amp could be the culprit.
If not, put back all patch cord where they belong.
Switch your speaker wires from your main to your surround.
If the Hum move to the surround, then the amp is at fault or the wires going to-it.
For the speakers, my only suggestion is to make sure they cross any power cord and patch cord like a + sign, but not in parallel, should not matter that much with patch cord, but we never know.
The last thing I can think about.
In my system I have two dictated 20 amp circuit one for my 2 subs and one for the amp, also one 15 amp for projector, pre-amp and blue-ray.
The one thing I made sure, all those circuit were on the same side of the main house circuit board (you have a left and right side and sometime with audio, it can introduce a Hum problem).
I also doubt it would be the problem since you got a Hum in your main only.
Lots of thing to try, and honestly Hum problem in a system can be the most difficult one to find the source.
Even when found, the cure can be difficult and this is why I made a suggesting of a new tread with more traffic.