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

@dover I already got an electrician over and it was the first thing he did. I demonstrated the problem with the phono preamp, he even brought a 12V battery and we had plugged the EAR into that. I have shared a picture in a one of the previous posts. 
Maybe I'll have to call him again, or I'll find someone else to be sure. I will consider getting the tester to do it myself. 
The building isn't that old, it's in the center but it's a functionalist building from the 50's. The power line could be 20-25 years old. I'll open up one of the sockets to take a look. The voltage is pretty stable too. The owner takes very good care of it.
I'll definitely call the electrician and make sure he checked it properly. But I think we even checked the grounding outside of the apartment. 
There's a different circuit in the kitchen, I tried to power up the EAR from there, no change nor difference in the noise level. I could run a power cable from a socket outside of the apartment.
I have finally bought proper power cables, they are on it's way. 
As soon as I sell the Classé power amp I'll get better interconnects too.
 

I have mentioned this issue in the conversation with the ARC staff as we were discussing the advantages of the ref150 over a ref110 (the use of KT150 tubes) and they basically said I should get the best interconnects I can afford and keep them short. 
 

And yes, I have tried lifting the ground in the EAR's power cord. 

@ghdprentice  the original idea was to find an ARC PH5, still affordable but all the ARC products are rare in Europe. So is BAT gear or Conrad Johnson. I have read how EAR compares to PH5 and I simply went this way.  
I'm a bit afraid I'd have the same issue with any ARC phono too. 
The REF150 is great, it gives a lot of room for improvements in the rest of the system. If I get an opportunity to get a good deal on an ARC phono I'll go for it.  
 

@filipm if you are going to open up a wall socket to check things out, might as well check for DC voltage on your AC power too - just put your DMM to DC volts and the probes on hot and neutral - I don't think it would cause this issue as it typically causes mechanical transformer hum and vibration and not noise in the signal path. However, I suppose the tubes could be picking up that vibration if present via microphonics - and it is another thing that might not be present in another location.

If tips from phono stage manufs including Jud @ Joule-Electra(RIP), Kevin@K&K and everyone here couldn't resolve it, it was time to move on. 

@sbank If that was a JE phono section, the input gain stage was so starved for current that it easily rectifies RF energy and so will be prone to RFI problems. I think Jud didn't want to increase the current to a more linear region as gain was going to be sacrificed.

@ejb14 There is a transformer hum in the EAR. I thought that's normal. There's also some hum in the LS16. Nothing too loud but when you get head close to the device in absolute silence it's audible. 

The electrician didn't make it yet. But I got the shorting plugs. It's the same as the shorting plugs I have made. It makes no difference at all. - that's kind of a hint. 

Anyways, today's hifishark found an ARC PH5 stage in Netherlands. I'm thinking of picking it up. It will be interesting to see if it acts the same. I was also always curious how these two compare. If the problem remains, I'll sell one of them and keep looking for the solution or I'll just sell both and get a solid state phono stage.

I think you might be right about the lifted ground. I remember bringing home my first dedicated phono stage. There was some kind of hum too. I don't really know what I did but it disappeared after a while a remained pretty quiet. I also had a Primare R15 phono stage, it wasn't quiet either, there was this white noise at higher volume but neither of them picked the noise like the EAR.

That was the first thing I thought of, the transformer is making noise and the tubes are picking it up. But I would never guess the noise of the transformer is caused by a lifted ground. I'll take the EAR somewhere else again and see if the transformer sounds the same. (I didn't mention it before because it's very quiet and seems normal)

@filipm - my calculations might be incorrect, but the EAR  amplifies a those low frequency signals (the mechanical transformer hum is a pretty low frequency I believe) something like 2500 times depending on how low the frequency. First an equalization of 20db for the bass region of RIAA, then another 48 dB for its phono amplification according to the EARs specs. I wonder if lightly touching the tubes with a pencil eraser (thus absorbing some of that mechanical energy) affects it.

This may be caused by the DC voltage on the AC power that I mentioned earlier - easy to check, and you can filter it with device that goes in serial with the power, like the Van Alstine Humdinger or I think iFi has one too. Good test to take it elsewhere to see if you still hear the mechanical hum. Supposedly toroidal transformers are more susceptible.