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

You have a very unique setup, where you're mixing balanced (XLR type) and unbalanced (RCA type) pieces of equipment together, and in a situation like that, they don't always want to play nicely. This is when ground loops can take place. 

Are you familiar with a ground lifter plug? I know we have them in the US, but I don't know if you have them there. I'd be interested in hearing what the EAR would sound like, if you lifted the AC ground to it, while still keeping the TT ground connected to the EAR. 

It also sounds like you purchased the EAR used, and I'm wondering if anyone has made some internal modifications along the way. 

>>>So I took the EAR to my friend's place. Horrible wiring, cheap components - absolutely quiet and great sounding.<<<

I'd be curious in knowing if his system has the same meshing of XLR and RCA equipment as yours does, or is his exclusively RCA unbalanced connected equipment?

@filipm the EARs transformer is pretty noisy mechanically at your place; suggesting a power issue. The battery test was interesting and you would think would rule out dirty power, but that may have also just demonstrated the same power issue - have you tried the battery test elsewhere (like at the friends place where the EAR sounds fine)? I suspect the same results. 

I listened to the noise again - the noise is a pulsing sound over what looks and sounds like a ground buzz. This may be a stretch, but perhaps your EAR's power supply is near end of life and when combined with the transformer issues at your place, is sagging and recovering rapidly, like a motorboat noise. It may not occur elsewhere because the wall power is just better enough there to allow the EAR's power supply to keep up. This would cause the tube circuit to generate the noise in the output regardless of input (search tube motorboating on youtube). 

Are the filter capacitors in the EAR's power supply original? They are probably over 20 years old at this point if so. I'd take those out and test them or just replace 'em.

@ejb14 

These had to be replaced. R16 died, the others were replaced along with it. 

It stopped working for a while as I was experimenting with it. 

I'm thinking of sending it to the factory, at least I will write them again with a suggestion.

@dpop I have also tried RCA only interconnects with two of these chains. For example Bryston B60 doesn't have XLR inputs. Now I'm only using XLR between a preamp and a power amp. 

33 ohms were measured on the EAR's phono ground pin or any screw (chassis) and the ground pin on the inlet. All the other solid state phono stages worked fine. Maybe except a Primare R15, there was a pretty loud surface noise, kind of like white noise. 

I always thought it was a subjective point of view, my girlfriend keeps telling me I only keep analyzing the system (of course when I'm not happy with the sound). Nevertheless I always had a feeling there's not enough juice in it, specially with the Bryston B60, it wasn't stable, sounded weak or lean sometimes. I was always surprised when I took the amp elsewhere. 

What else can we measure on the AC line when an electrician comes over? 

There's a simple voltmeter on the power conditioner I'm using for the sources. It shows some drops time to time, it's usually around 228-229V but it goes down to 225. If we find out the AC line is horribly dirty and unstable, is a power plant good idea? Something like PS Audio PP12 (I'm just a bit confused now, I have seen some measurement that suggest it's an overpriced piece of crap and I'm being told to stay away from power conditioning)