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This 60 Hz hum is driving me crazy

I just got a new to me, Prima Luna Prologue Premium Integrated tube amp. Sounds great, but there is a "ear to the speaker" 60 Hz hum. Hum sounds the same if I adjust volume +-/  The only thing I have connected is a Parasound Zdac.  Speakers are Rega RS1 Here is what I have tried:

1. I disconnected the Zdac so it was just the PL connected to the speakers with no other inputs. Hum still there.

2. While Zdac still disconnected, I use a 3-to-2 prong adpater to determine if its a ground loop.  Still there.

3. The outlet is a new one added from our remodel.  So I used an extension cord and plugged into an original outlet to see if the electricity was "dirty."  Hum was still there. 

Now here some possible culprits.  

* The stereo is perhaps set up in the smallest man cave in California.  The speakers are about 2 feet away from preamp.  I will try moving speakers further. 

* I am using crappy Amazon 12 AWG cables.  I have some better ones coming from Morrow Cables. 

* The stereo is in front of the panel that our internet wiring comes in through (I am in a condo complex).  There is no wireless there, but perhaps I should set up system somewhere else to try.

* I am using the tubes from the previous owner...do I just buy a set of new tubes?  

Is there anything else I should try?  Thanks in advance.

 

comedyzen
coach67's avatar
coach67
17 posts
 

I had the same problem a few years ago. Even took my amp to the shop because I thought it was coming from there. But there is this thing called DC Offset. You can google it. There's something in the wiring of your house. It's not your gear. I found the CMX -2 precision common Mode  AC line Filter with DC Offset Eliminator. You can find it on the Emotiva web site. Does not affect the sound and gets rid of the hum. Check it out.

comedyzen OP
15 posts
 

thanks Coach.  This is great info.  Going to try a few more things but will def add this to the list if all else fails.

sns
3,464 posts
 

Yep, dc offset can be problem, check your house grounding system.

comedyzen OP
15 posts
 

Now that I think about it, both plugs I used were new ones from remodel from contractors who I would never use again. Hmmmmmm...need to try another outlet...unless they compromised the entire home.

paradisecom
339 posts
 

Another grounding issue I had was from the cable TV box. There was a splitter on the outside of the house, which needs to be grounded and it was, to the steel conduit/ main breaker panel just above it. But, that grounding clamp and steel pipe had been painted so it wasn’t making a good bond. The resistance from the splitter to the pipe should have been 0 Ohms, but it was measuring about 10 ohms iirc, which isn’t much, but it was enough to cause the cable box to hunt for a better ground inside the house, inducing some hum. Once I cleaned everything with a wire brush on the outside of the house and got a good bond measuring 0 Ohms, the problem was solved.

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