Tube PHONO preamp interference - RFI, EMI, bad grounding?

@lewm - an excellent point - I was assuming the OP was on 50Hz AC power, based on one of his previous statements in this thread, and the circular plugs in the powerstrip in one of the pics he posted.

@filipm - are you on 50Hz AC or 60Hz AC power? (should have asked this question earlier.)

I plotted the noise spectrum in Audacity, and the 50hz buzz/hum is constant throughout the entire recording at around -17db though it does have very short spikes to -13db intermittently (I think this is the intermittent bursts lewm is talking about). And then there is another spike of a range of frequencies every four seconds.

From the Bottlehead trouble shooting guide:

"Buzzy hum, like a bee - This usually means a lifted ground connection. "

if a lifted ground, then where it is lifted is the question, but a cold solder joint is certainly possible, though I would have thought if so it would have shown itself when the EAR was used at an alternate location. 

@lewm  @ejb14 I should have mentioned I live in Prague, Czech Republic. The voltage is 230V and the frequency is 50Hz. I posted it on a local forum but got quickly annoyed by the same jokes some people have been posting for the last two decades over and over.

I was in Berlin yesterday and took my EAR along. It worked perfectly fine even with the cheapest power cord and the interconnects I was using here. I didn't get the tubes yet but I returned with an ARC REF150 power amp. What a beauty.

Ejb, I'm now gonna read the article you have sent. Thanks. 

Exactly, if there was a lifted ground on the EAR, it would have been apparent at least at one of the locations I have been to. I wanna try to bring a small intergrated amp and plug it in on the hallway to eliminate the circuit in the apartment.

Is there any test I can do inside the apartment? I invited an electrician and he said the power line should be fine. 

@filipm  You could get an outlet tester from Amazon or a hardware store - one that would show open ground/earth would be important. Search Amazon for "outlet tester Prague" (or UK) - You can also use your DMM to test (google how to do it, lots of hits) - just be careful - and use just your right hand to place the probes - do not use both hands - if the outlet is not connected to ground, you don't want to become the ground. If you can, I would get an outlet tester. They are cheap and a great thing to have in this hobby. You likely want to test your power cords too for ground correctness.

I've been in and tested many homes and apartments. Not all were wired correctly, even the newer ones. Check all outlets.

Is there any test I can do inside the apartment? I invited an electrician and he said the power line should be fine. 

Beautiful city Prague.

If you are in an older building, you should get an electrician to verify the male earth pins in the building are in fact grounded. They may not be, or the grounding may be compromised with poor connectivity - corrosion etc.

Also if both the EAR and ARC are grounded through the power cables, then when you connect the 2 units with an RCA cable then you have an earth loop - have you tried lifting the ground on the EAR ( making sure iit is grounded via the ARC by putting a multimeter across the 2 chassis.?

OP,

Congratulations on the ARC REF150. Great sounding amp.
 

Now, I would recommend you give up on your EAR and get a ARC PH8… or better yet a ARC REF Phonostage. Each additional piece of ARC is incredibly synergistic… culminating in a really amazing sound with all ARC. Although it makes sense in retrospect, I was really surprised when I dropped in the final ARC piece in my system.