Help me to understand something here. You have everything disconnected from component to component and no AC applied to any component and you still have a hum coming from behind your component rack ? Sean
Tinfoil under my hat works for me...
Why do you think it's RF?
Do you live in a multi-unit dwelling of some sort or a house?
City or country?
What's downstairs, upstairs, and next to this room?
Sounds to me like something mechanical, not electrical, and it's causing some microphonics issues in your gear when it's on.
Mooncrikit sent me the following via email:
I live in a single story family housein the suburbs on a 1/4 acre lot. I moved my amps and preamp and speakers and cd source to the other side of the house with no change. The only part of my gear that would be sucseptible to
microphonics would be the preamp, which is tubed, but I borrowed a buddies AR-LS1 and the same [stuff] was happening. I figure its RF since I shut down the main circuit breaker to the service panel, unplugged all gear from each otherand the wall and can still hear a humming onlt in this area of the house.
Well, I have no idea unless you live next to a giant power transformer and didn't tell us.
Sounds like it might be 60 Hz hum from a transformer of some kind, but that only occurs if there is something powered up. Any chance you might have low voltage halogen lights on a different circuit breaker? If you still hear it and the whole house mains breaker is off, you may want to get your ears checked--might also be tinnitis...
Assuming that Edesilva might be on the right track about a very strong electromagnetic field (EMF)expanding and contracting at 60hz frequency from a rogue external power equipment, your speaker cables can pick up that like a wire-loop induction. If your speakers are efficient enough it might be playing the hum all day long without your amp turnon. I can be wrong, but try disconnect your speaker cables and see if the hum is still playing.
I do hope I'm wrong in this intriguing Mooncrikit case. There were many health concerns raised by people who live near sources of EMF recorded by Mark A. Pinsky in his book "The EMF Book" 1995 Warner.
I corresponded with Mooncrikit briefly and from what i can gather, Edisilva seems to be on the right track. It is almost as if there is an external source for the vibration / hum. Only problem is, Mooncrikit has experienced this when the AC mains were disabled, meaning that the power to the entire house was not functional. As such, it looks like Philip's suggestion about an EM field could be coming into play here. I have experienced this problem to what most would consider a "scary" and very visible extent before, but not inside of a house.
As to try and narrow things down, how far is your house from a large pole transformer ? Do you have High Voltage power lines in close proximity to your house ? Is the AC feed into your house in very close proximity to this room ?
To be quite honest, this sounds rather baffling to say the least. Sean
This is a real shot in the dark, but check to see if you have a thermostacially-controlled vent fan in the gable end of your house. When I moved into a house once I did not know one existed. I keep hearing a damn humm, but only in one room, and only on occasion. Now, if you have truly disconnected power from the main, my point is moot.
yes check your attic for a attic exhaust fan ours is quite noticeable if your near the wall where its mounted into. But killing the power to the entire house should turn its power supply off also? or possibly do you have any of those round attic vents they aren't powered by electricity they work through the heat rising it could need new bearings if you have any.
I am getting dit dat from a ham operater keying somewhere. I just ordered some material that is supposed to shield from RF. I have a
SOTA sapphire turntable and Hana low output moving coil on a unipivot Ultracraft tonearm. It is a function of where the cartridge is located above the turntable. It is highest when not above the turntable platter but outboard of the record perimeter the noise has some varation in volume and stereo channel it is on depending on the location over the turntable. It does not disappear at high volume but is still apparent over mostly the outer edge of the platter but over the outer inch or two of record grooves.
I have tried different tonearm pipes(the tonearm has changable "pipes" not changable headshells), and tonearm bases. It is present on a Hana low output moving coil and also on a moving magnet Grado mounted on a second tonearm pipe. Different tone arm cables make a minimal difference in the amount of the noise. I even tried adding ferrite chokes over my tonearm cables
The ONLY cure for RF (radio-frequency) interference is a Faraday cage; however, as others have mentioned, RF is hardly likely to be the culprit. Most likely, it is EM (electro-magnetic) interference rather than RF. As someone has mentioned, transformers related to other equipment are likely to contribute to audible 60Hz (and harmonics) noise. And, if your system is improperly grounded (or there are ground loops) it is extremely easy to have that noise induced into your signal. Likely culprits are the power supplies associate with low-voltage lighting (often halogen and/or LED), florescent lighting, door-bells, and some of the smart-home controllers that inject additional signal on top of the A/C line.
Given that most high-end gear-heads tend to spend ridiculous money on various interconnects, that is an unlikely problem. Some (poorly designed) preamps do not ground or terminate un-selected open inputs, creating a possible source of noise induction. Speaker cables, also, can pick up induced hum.
Cheap but VERY effective speaker cable formula:
The resulting speaker cables can carry more current (and voltage) than even KW-rated amplifiers can produce. Moreover, they are as immune to induced signals as anything commercially available without going to shielded conduit. And, they cost relatively nothing. Win-win!
As for RFI, keep all your cables as short as possible and use shielded power cords. They should be three conductor plus shield. The shield should be connected to the male end only. The best way to make sure thi is the case is to make your own which you can easily do at the state of the art. You can even make them look sharp if you care. I don't. Use balanced cables everywhere you can.
If you still have trouble then you will need to move.