2. amps-preamps
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Ground loop feedback - cable wire issue

After installing an amp there was a ground feedback low hum noise. Muting ht system made it go away but not a good solution. Also, routed cable thru surge protector and this substantially reduced problem, but still slightly there. I don’t like using surge protector.

cable co came and grounded cable wire. But this did not solve problem and I still need Cable wire to go thru surge protector. Outlets in room all controlled by one circuit. All components except tv and amp share a surge protector. Tv goes thru power conditioner and amp plugged directly to wall.

disconnecting cable wire eliminates feedback noise, even after being grounded.

Seems amp related, not sure why.



emergingsoul
gdnrbob
4,450 posts
 
To lift a ground means you remove the ground pin.
You can do this by either removing the ground pin from the plug (not recommended), or using a ground cheater:
https://en.wikipedia.org/wiki/Cheater_plug.
As your Marantz has only 2 prongs, then this is moot.
I will defer to atmasphere with regard as to how to proceed.
He looked at my equipment when I had a similar issue.
Bob
atmasphere's avatar
atmasphere
11,850 posts
 
@emergingsoul   Is there a TV involved in this setup?

emergingsoul OP
1,182 posts
 
Yes, there is an HDMI cable between tv and avr.

tv is plugged into a power conditioner.

thanks
saika2
31 posts
 
"You can only do this if the preamp employs a 2-prong AC connection! "


Actually, can be done with a three prong connection as well....just have to switch the live and neutral within a plug of an ac power cord, and resupply the "noisy" preamp or amp ...in some cases the noise will be less........lifting the ground is way to break the ground loop, but is fraught with electrical shock hazard, although it can be a useful tool or trick to determine the origin of a ground loop...some preamplifiers - eg the Herron VTSP series have polarity switching toggle switch at the back to enable this to reduce "noise" in the system.
jetter
3,035 posts
 
This is what solved the cable tv ground loop problem for me, worked like a charm:

https://www.bhphotovideo.com/c/product/1344635-REG/jensen_transformers_vrd_1ff_cable_tv_capacitive_based.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gclid=EAIaIQobChMI_966mNDx6wIVGU2GCh0JEQEkEAQYASABEgIdlvD_BwE
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