HELP. can’t stop high frequency interference.

[coledfriesen]

I’ve been working out of a project studio for about 6 months - it’s an older building with some dodgy looking power.

I haven’t had any real noise issues until this week and there was terrible read up screeching frequencies coming through my guitar amps, my tube mic - even at a lower volume through my monitors.

I got a furman power conditioner and no matter what outlet I put it into, if I turn the heater off, the lights off, unplug everything else in the place I’m still getting this crazy interference.

Is there something I’m missing? It wasn’t there and now is. Please help.

[Martin Walker]

Hi coledfriesen, and welcome to the SOS Forums!

High frequency interference is often associated with ground loop problems where digital gear is connected, but it's normally at a low level. However, 'screeching' (aka howlround) sounds more like some sort of feedback mechanism, where a signal get passed back earlier in the audio chain and then gets amplified.

In the UK power conditioners are rarely needed, but even if you're not in the UK I doubt that the Furman device is altering anything to do with this interference, so I suspect that's a red herring.

If this interference 'wasn't there and now is' you must have changed something, perhaps a gear setting, or accidentally plugged an audio cable into the wrong socket, but the only way to track down the reason for this problem is for you to systematically unplug gear until the noise stops, which will narrow down the culprit.

Failing that, you'll need to provide a lot more detail on what gear you have and how it's connected so that we can offer more specific advice. It may also help if you can record a few seconds of this interference and host it somewhere so we can listen to it.

Martin

[coledfriesen]

Hey Martin,
Thanks for the response. Hard to fully narrow what it could have been as I’m always plugging, changing and rearranging my setup as sessions require me to. Spent a bunch of time trying to isolate the problem and didn’t fully sort it out.

I did manage to being the interference down to a more manageable level and will continue to attempt plugging and unplugging various things. I’m in Canada FYI.

I noticed today that if I love my amp around while the “screeching” is happening it morphs as I move around the room so I thought maybe it it’s the amp that needs a look at. Tried every outlet and had the same problem, tried using an active di box direct in and the problem was still there, tried anything I could plug into the wall and there was still a small amount of noise from all sources and outlets.

[Wonks]

Have you noticed any new phone masts or radio masts in that area or even on the building, that weren't there before?

Are you close to a military base of any kind that could have moved say a portable radar installation or truck close to you?

If there are multiple let rooms, somebody could be using something outputting a very strong RF field that is being picked up by your equipment.

Have you tried a battery powered portable radio to see if that also picks up the screech?

[James Perrett]

Are you surrounded by other people in the same building. Could one of them have bought a gadget that emits interference? It could be a dodgy switch mode power supply in some piece of kit or even a fluorescent light. Some fluorescent lights emit quite a bit of interference just above the audio band so it is possible that a faulty one could be interfering in the audio band. Even power line networking plugs could cause problems although they should be out of the audio range.

Are you using any radio devices? Have you checked your sockets with a socket tester? In the UK you can buy socket testers for a few pounds.