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Thread: Trying to identify an intermittent noise caught by instruments pickups

  1. #1
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    Trying to identify an intermittent noise caught by instruments pickups

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    Hey!

    Newly registered here! I'm trying to find help identifying the source of an intermittent noise that's being picked up by my instruments pickups. It's not a 60hz hum. I could deal with a constant noise being part of the "character" of the instrument, but the intermittent nature of this noise kinds of bugs me and I'd really like to get rid of it from my recordings.

    I attached a file - the volume is massively boosted, but it's pretty easily audible at normal volumes. I only get it with an instrument plugged. This is my bass with single coil pickups, both at full volume. If I turn down either of the pickups, I get the characteristic background hum of single coils, but the intermittent noise still comes through. I also tried with a guitar with humbuckers - the noise was considerably lower, but I could still hear it. I tested with three different instruments.

    I tried powering off my computer screens, desktop speakers, a nearby ceiling fan with lights, turning off the wifi from the PC itself (but didn't try powering down the router that feeds the wifi around my appartment yet).

    It *mostly* goes away if I put my hands on the strings or on the bridge, or touch a metal object on my desk (e.g. the DI's case).

    Any ideas?
    Attached Files Attached Files

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    Sounds like a bug zapper.

    When I hear a timed pulse like that...I look for some electronic device that could the culprit. I mean, it's not a ground loop or just your more typical AC noise.
    That's a repeating pulse of some kind that appears to be on a 5-6 second cycle.

    Speaking of electronic pulses...I was just dealing with that issue as it relates to the new "Smart Meter" and "AMR" meter technology that is being rolled out nationwide by the power companies.
    There is a lot of argument against them...though the power companies are trying to push them through....but now many are offering op-opts.
    What's that got to do with this thread...well...these new digital meters emit very high EMF spikes in order to transmit their data...though the newest "Smart Meter" units are even worse, and they are continuously running on a wireless WAN network, constantly emitting RF signals, like a microwave.

    Not that I think your problem is that...but just to point out there are all kinds of electronic devices that will cause noise in the electric lines.
    The irony with these new meters, is that it's the power company that is introducing "dirty power" into their own electric lines...not to mention the health issues caused by the 24/7 RF transmission at very high levels....plus the fact that now the power company will monitor your every device and know any time you power something on/off in your house. Talk about Big Brother.

    I still say your problem sounds like a bug zapper.

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    PLEASE tell me you have a digital test meter?
    If so check the conntinuity from the jack body to the bridge. Should read less than one Ohm. Similarly the case of the DI should read very low to whatever it is plugged into?* If not it should read low to the input jack sleeve.

    You seem you see to be missing an earth bond? Since, AFAWCT, you are running: Bass>DI>AI(?)>PC there is no fear of a "ground loop" and so any earth lift switches should NOT be lifted. Does the whole setup eventually find mains earth?

    The noise spectrum is a wide band pulse centred at about 4kHz and thus not likely a "coherent" source like a radio station. An electric discharge "zapper" would seem favourite. It is important to know if the noise is being picked up on the guitar cable or gets into the DI anyway. Do you have a guitar pedal? If so, plug that in sans guitar and check for noise.

    *Where does the DI plug in? An interface? Mixer? Directly into a laptop jack? If an AI, what happens if you go directly into the instrument input of that?

    Dave.
    Attached Thumbnails Attached Thumbnails spec-ins-noise-png  

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    Although it doesn't sound like what I've heard from them before, but could it be a cellphone signal? The usual sound is a "ditditdddddit" but perhaps this is something with newer phones.

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    I suspect a digital monitoring system - electricity, water etc - they all send data bursts.

    one thing to try - if you use the single coil pickups, then as you rotate, they can be useful to direction find. The interference comes from the line off the pole pieces, so you can get a rough bearing keeping in mind it goes forward AND back. If you move in the room, you should get two directions and where the line crosses is the source location. Closeness to the source also changes the volume - so walking around can help you locate it. That doesn't fix it, but gives options. touching the screening with the hand does do a couple of things - creates a high resistance path, through you that dampens the noise by shunting it to ground, and it also makes your body a shield - a conductive mass that can mask some of the EM fields that are around. It's also a good short cut for any fault currents that can suddenly appear, and hence in some circumstances, can kill you. The ground of the guitar and the metalwork should already be grounded - and this may not be the case. Touching strings and hearing noise going down is always a warning.

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    Wow! I did not expect such indepth replies, you guys are amazing!

    miroslav
    Haha, you're not the first one to make the bug zapper joke! If I ever need bug zapper sfxs, I'll know where I can find 'em Interesting about the smart meters. I'm on the second floor though, and I think they'd be set up at the base of the building if we had those, right?

    ecc83
    I don't have a meter, no! It's my first time trying to debug this type of problem, and I know next to nothing about electricity and interference, so bear with my newbie questions for a second here;

    * What is an earth bond, and how can you tell I'm missing one?

    * I am running bass -> DI -> interface -> pc indeed, all through brand new high-quality Mogami brand cables.
    20190709_073010_hdr-jpg

    * Earth lift switches - I assume you're talking about ground lift switches; the Ground switch on the DI is set to Gnd, not Lift, though I tried both and I hear no difference.

    * Plugging into pedals without a guitar -
    I don't get the noise when plugging into my pedalboard (disconnected from a guitar at the output end)
    BUUUUUUT, I DO get it if I touch the tip of another, disconnected instrument cable with the cable connected to my DI (along with a loud hum).

    * RNDI (active) into Steinberg UR44 interface (input 3 - a Mic/Line input, gain is at ~1/3rd). The DI is being fed +48v by the interface. I went and tried plugging the cable directly into the interface's four inputs, without the DI, and I get less noise plugging into inputs 3 and 4 directly (Mic/Line; though it's still there, only much lower). Inputs 1 & 2 (Mic/Hi-Z) give off about the same noise level, plus a loud electrical buzzing. The UR44 manual says this about the inputs;
    2019-07-09-07_57_01-window-png

    bouldersoundguy
    Yeah, I thought about it. I took my cellphone to the bass pickups and could hear the signal very clearly, then turned it off to see if the intermittent noise would go away - still there.

    rob aylestone
    Cool, I'll look into that. I did notice the noise getting louder along an axis, and as I got further from my PC towards the room at my back. I'll see if a quick treasure hunt could lead me somewhere interesting I do hear noise go down if I touch metal, but keep in mind I'm amplifying the noise pretty radically right now to keep it easily audible. I assume even in a best case scenario, there would be some slight variance between touching/not touching the strings? Again, electricity newbie here.

    ///

    My next tests are moving around the place with the bass, trying to find a source for the noise, and failing that, making my setup mobile with a laptop and trying to find another location in the appartment with as little noise as possible, though that's only a temp solution (but I'm supposed to record bass in the next few days, so that's gonna be that if everything fails).

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    Just looking at your picture, and what little I can see of your physical setup...you've got a bit of a cable rat's nest that should be cleaned up, and you should separate the power cables from the audio cables and avoid running them all on top of each other.
    The other thing I notice is your audio interface/preamp is wedged between the computer monitor and the speaker monitor. I would not have that there.
    I don't know how else you have things...maybe you should post a few more pictures.

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    You are absolutely right about the cables at the back of my PC, and I suspected as much about the interface being placed there not being such a good idea.

    I just spent the morning doing these tests;
    * turning off / unplugging (in case of standby) all devices at home (except fridge, oven and eeeerrr the coffee brewing machine )
    * installing Cubase on a laptop and moving my setup around the appartment - making the mess behind my PC and the placement of my interface kind of a non-factor here - I tried in the same room a few feet behind me, in the dining room (on another circuit), and in the furthest room from this one, at the opposite side of the appartment (on yet another circuit).

    I've had various amount of continuous noise in all the places (laptop on battery was the noisiest scenario by far) but in all cases, the intermittent noise was always still there - which leads me to, yes, the cables and interface placement on my desk is less than ideal to say the least, but I don't think it's responsible for this specific noise which is my priority target right now. With the exception of that damn intermittent noise, I'm getting a suprisingly clean input with a very low noise floor - considering this is a home studio in an old appartment building scenario. Also, I can now confirm I get the noise without a guitar plugged in - I can get it with the instrument cable disconnected from any instrument, loose.

    I'm about to try
    * a different audio interface - I'm starting to think, as it's one of the few common denominators in all my tests, that it may mine that's producing that noise internally (but then, why do I need to plug something in to hear it? Preamps?).
    * expecting no result here, but for the sake of thoroughness, fiddling with driver settings inside Cubase

    Here's a panorama pic of the room I'm set up in, in case someone spots something - but I did try turning off and unplugging everything you see in there.
    20190709_141447-1-jpg

    The room we see through the doorway on the left has nothing going whatsoever in there. Then you've got my girlfriend's work PC corner. My PC is at the center, to the right you've got my living room setup.

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    Actually - I had to smile when you posted the picture of the guitar. I've got an American Standard 5 string bass and it would pick up things in some venues and be totally quiet in other places. I bought new pickups, lined all the cavities with copper foil and the noises went away. The culprit was eventually tracked down to a switch mode PSU in our stage rack, which is only 4 feet away from me in most stage setups. The Fender pickups just seemed to really hate it. in truth, maybe the foil would have done the job?

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    I like that guitar, though I may be biased.


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