505 hums when receiver turned off

[daslolo]

Is this normal ?

I notice that when I disconnect LFE jack from the rear of my 505, the hum ceases.

Thanks.

[Airplay355]

ground loop maybe?

[daslolo]

What is this and how do I fix it ?

[Airplay355]

I'm not really sure and I don't know. I'm not even sure if thats what your problem is. Sorry lol. Someone who can help better will show up, don't worry.

[Tour2ma]

Don't think it's all that uncommon. My Carver M1.5t produced a hum when I shut down my pre-amp. Right or wrong I attributed it to interrupting their common ground when I flipped the pre's power switch.

Simple solution, leave the AVR on... For vacations and electrical storms shut both the AVR and sub down...

["Polk" Paul DiComo]

Sure sounds like a ground loop to me. Here's a simple way to troubleshoot the problem - disconnect any cable TV, satellite TV or antenna connections from the system even if they are not hooked up directly to the audio system. If the hum goes away the ground loop is the result of the cable/sat/antenna ground and is cured by putting on a ground isolator http://shop.polkaudio.com/customer/product_info.php?cPath=6&products_id=38

If that doesn;t do the trick, use those 3 prong to 2 prong adapters to "lift" the grounds from each component in your system until the hum (hopefully) goes away. If that doesn't work, let me know and we'll see what else we can do.

[RensoPLC]

Any time you have subwoofer associated hum it is 99,9 percent due to a ground problem as stated in an earlier reply. I would bet that it is most likely due to a bad cable. Yes when these audio cables go bad the internal wires touch (ground to signal) and this will happen.

try a new cable or at least a spare ne you may have !

I hope this helps