@hagtech What RF filter are you using? There's many and don't know anything about these.
Looking at the guide, it's definitely not hum or buzz. I know what to do to make them appear.
This is a very sharp beeping sound with a pulsing bass driver, I have posted the sample afterall. It's the same every time.
What's interesting I can hear the same noise coming from my laptop charger sometimes. Of course it's not the source, one of the first things I unplugged.
@lewm I have taken the cover of the EAR off, with the tubes exposed, the noise doesn't get any stronger. Do you think the interference could get into the Faraday cage and be stopped by these aluminum hats? Maybe I could use an aluminum foil instead, just to see if it makes any difference.
I'll try different tubes next week, even tho I have read they cannot be returned. Mullard CV4004 or Tung Sol gold pin.
@perkri yes, the tubes are sitting well in the sockets. I have taken them out and changed their positions too.
@theaudioamp The building isn't the tallest in the area. I have checked the google map, recently updated by the way and there's nothing visible on our roof or on any roofs near by.
An electrician is gonna stop by with a 12V battery that can power up the phono preamp. That should definitely eliminate a possibility of a noise coming from the electrical network.