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

Get one of those cheap yellow outlet testers at Home Depot and see if the new outlets where wired correctly.

If your using tubes from the previous owner you have no idea how many hours they have on them.  I would say replace all the tubes and go from there.  I bet that solves your issue.  Others commented on a possible DC Offset issue but this usually manifests itself as a humming from transformers in your equipment and not a sound through the speakers as you describe.  Before you do anything...replace the tubes as that to me is the most obvious cause.  

 

@dill got the little $6 yellow tester (figured it is good to have regardless).  All outlets I have been using were OK.

Also moved the amp out of my mini man cave into the living room and plugged into another outlet....and the hum is still there!!!

I ordered the iFi DC blocker from Amazon to check that next.

My new speaker cables came in too, and no help.

If the DC Blocker fails, I will try replacing the tubes.  Does anyone recommend a solid place for both price and good tube reputation?  

 

For tubes I suggest Jim McShane or Brent Jessee. Both have websites and are good sources for tubes. Jim for good prices, Brent for the best.

You might have a ground issue inside the amp. I had one in my phono stage that was fixed by removing some paint from under the chassis ground wire. There was not enough bare metal exposed to make a good ground. The paint was acting like an insulator.