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Interference across vintage receivers - Marantz/Pioneer/Eico

robbymo

robbymo

New Member
Hello AK - I posed this query in the tube amp section a few days ago but it appears this problem is occurring across all my receivers/amps. I'd originally heard a high pitched noise in all channels in my EICO HF-81, sounding a bit like Cell Phone interference of yore ... a faint squealing noise a bit like a dot matrix printer. Cleaned the pots/connections as advised and the problem still persists.

I've subsequently plugged in various solid state receivers including a Marantz 2230, Marantz 3330 + 140 preamp/amp, Pioneer SX 780 through different speakers, different power outlets and different rooms and am getting the same noises through all in varying degrees. The sound increases with turning up the volume, and listening in the preamp stages.

I've disconnected wi-fi routers, power strips and any lights that might be causing this but the problem persists. I live in an apartment building in NY. The problem started a few days ago and my neighbor has cited a strange noise in his clock radio - not sure if there's a relation.

Any other ideas to help diagnose?
 
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I'd guess since you live in an apartment there's other people living near you. It could be any one of them (within 250ft or so) with maybe a bad power supply in something, or a bad light, among other things. If something is making that much RF noise it's a malfunction. Just as it appeared, one day when you're not paying attention it'll disappear. Whatever it is, it won't last long doing that.
 
Certain Ham radio transmitters can cause all kinds of interference. I was at a friend's house once and I heard an amateur radio transmission very, very clearly on my friend's ... washing machine!
 
Well, nothing is easy with interference. You first have to determine whether it's coming through your power outlets or over the air. Checking with your neighbors might not be a bad idea. Next there are power conditioners, but they won't help with over the air stuff.

Good grounds really can help with over the air noise. Also for non-polarized plugs, you should try reversing in the outlet. Start by unplugging everything and then plug in just your main amp/receiver. Test to see with no input and your volume full on, do you still hear the interference. If yes, try reversing the plug if it's non-polarized. If you still hear, I'd guess it's coming through the lines as most amps/receivers are shielded quit well.

Have you looked over the sticky topic on ground loops? AK has tons of good information in these "sticky" topics!
 
Thanks, I'll give that a shot. I just learned from a neighbor that the building across the street may have put a cell phone tower up. Am I out of luck if that's indeed the case?
 
It is likely not an amateur radio operator because the signal, in this cast the interference would not be constant. The interference may or may not becoming from a defective in the sense that failure is imminent.

The interference (RFI/EMI) can be conducted (such as through the AC mains) or radiated (coming through the air) or a combination of both.

A battery operated AM/FM radio can be used to try to track down the source.

Below is a video just for general information that gives some examples of devices that may produce unwanted interference.
While he gives examples of radiated interference, any of these devices might couple interference into the AC mains. Then a couple of things may happen, the interference can be conducted via the AC mains wiring to the impacted devices, our audio gear or it can be radiated by the AC mains wiring and picked up by our gear or a combination of both.


Something as simple as building maintenance changing one lamp with another can be an issue and so on.
The possibility of a close proximity cell tower could be another can of worms. A cell phone tower is not going to automatically be an issue, but there can be issues with the installation.

The go to tool in these cases is a spectrum analyzer. It will allow one to see, hear track and document the interference.

In a perfect world all of the devices would live up to the manufacturers' claims of "no problems".
 
Look for anything with a SMPS (switch mode power supply) in it. It could be anywhere. Listen with an AM radio like a RF sniffer.

You will find high frequency switching supplies in these items:
Laptop computers.
Laptop power supply bricks
CFL Compact flourescent lights
LED lights
VCR/DVD/TV power supplies
Set top and cable boxes PSUs
Microwave oven PSUs
Printer PSUs (power supplies)
All small lightweigh chargers (phone/baby monitors/camera battery chargers/routers/xboxs etc
Drill and power tool chargers
Garage door opener power supplies
PC power supplies - even when they are soft off.

And, Many many Xmas tree lighting power supplies!

It could be your neighbours too. Good luck :)
 
Hmm, it's intermittent. Almost sounds like bursts of data over broadband or wifi. But what do I know. Very little actually.
 
The issue is occurring in different rooms, with outlets on different breakers. Would that indicate anything?
 
Upon hearing it, that sounds like some kind of telecom equipment. It's not the sound of SMPS power supplies. What you're hearing is digital data of some kind. Quite a few digital electronics put out sounds like that, but they usually only go a few feet. Cordless phones can throw out noise that's fairly powerful like that, but they don't usually make that sound.

Have you tried using an AM radio to locate the noise. You can use a battery AM radio tuned off station as a crude RF sniffer. The old analog ones work best for that, they receive front and back, but very little from the sides due to antenna construction, this helps to find the direction of a signal.
 
ramzilla said:
What about hooking it up at the office?
Click to expand...

robbymo said:
The issue is not isolated to one receiver, it's occurring on 4+ different devices!
Click to expand...

The suggestion from ramzilla would test whether your apartment building's electrical and RF environment are to blame, which seems almost certain to me. As repair_guy says, it sounds like data communications to me. A new cell tower would be a prime suspect. The wiring in old apartment buildings can act as a giant antenna, and if you live right near actual giant radio towers, like I did, well, it went away when I moved...
 
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