Hi, I apologize in advance if this is not the right way to “reopen” this topic of mine, but I couldn’t figure out a better way.
As I said in my topic, I’m experiencing this very weird beep which randomly (usually with a maximum interval of 5 minutes between occurrences) comes out when connecting my guitar to the PC through my M-AUDIO MTrack II Plus audio interface.
I’m back to writing after TONS of tests, in which I tried pretty much everything…: Getting my phone away from the room, taking down the power supply of the apartment, changing jack/signal cables, audio interfaces, buildings (I live in an apartment building) and even CITIES…
Below are the results of my tests:
Software doesn’t seem to be involved, as I can hear the beep also if I set the audio interface to “direct” (as suggested by @ccaudle), routing the signal flow from the guitar input directly to the speakers/headphones, without passing it through the PC.
PC hardware doesn’t seem to be involved, as I can hear the same beep using my laptop and my desktop PC
Musical Instruments doesn’t seem to be involved, as I can hear the beep just plugging one end of the jack into the audio interface and leave the other one unplugged. Although I noted that the beep doesn’t seem to occur when connecting my microphone (which uses an XLR cable), but it is coming back if I only connect one end of the XLR cable to the audio interface and leave the other one unplugged
Changing Audio Interface doesn’t seem to affect the situation: I tried the Focusrite Scarlett 2i2 (3rd Gen) audio interface and beep still occurs.
Changing cables doesn’t seem to affect the situation: I tried either my “not so well shielded” jack cables and cables which should be shielded better like Roland’s and beep still occurs. I also tried to connect my audio interface to the PC with this cable with ferrite chokes suggested by @Schmitty2005 but nothing changed.
The only weird - as much as “weird” means in this VERY WEIRD issue - thing I noticed about cables is the one I described above about hearing the beep when my mic’s XLR cable is disconnected from the mic and not hearing it when connected
I tested the setup also in another apartment within the same building, in an apartment within another building in the same city (just about 50m away from my home) and in an apartment within a building located in another city about 33km away from mine, finding out that I can hear the beep in the other apartment within my same building and in the apartment 50m away from me; while I don’t hear the beep in the apartment in the other city
As I said, the beep seems to come out randomly, everything I was able observe was that it usually comes with a maximum interval of about 5 minutes between occurrences. I also noticed that in the night it seems to happen less frequently, there were a couple of times when I tested at 2/3 A.M. and didn’t hear any beep for about 10/15 minutes
Of course, keeping my phone distant from the audio interface (e.g. another room of the house) doesn’t seem to matter, beep still occurs. The same happens taking down the power supply of the apartment, still hearing the beep
As suggested in this topic I also tried to download the “Ultimate EMF Detector RealData” app in my phone and I scanned for EMF values the area of the desk where my audio interface is placed and found a value of about 20 microTesla. However, I don’t know how reliable this measurement is, as it seems to change a lot after very small movements (we’re talking about centimeters) within the same area of the desk and considering that the value of the measurement increases greatly when I bring my phone closer to the right side of the audio interface, thus reporting a value of around 24 microTesla when I place the phone on the left side of the interface and values up to 170/180 microTesla when I place the phone on the right side of the same interface.
What’s even stranger to me is that these values are detected even when the interface is not connected to power at all.
Looking at all these tests the issue seems to be some sort of interference, but I couldn’t understand the nature of the interference and how to avoid it… I hope for your kind help in this because now I really can’t figure out anything of this…
Tough one. Throwing in stupid ideas:
Aliens? No, no, but what about radar beams and the like. Very strong signals from radio, TV, etc.
? Any sort of external radiation source?
Because you are not getting the beep at that other city …
Did you try changing the operator ? I mean seting everything up so that the beep occurs and let a friend try again while you stay away (or let the computer record alone) ? Since you tried changing everything else…
Actually no, I didn’t. I just involved my guitar teacher just to test the issue with his cables (Roland ones) and to be sure not to be crazy hearing that damn noise… But I always were there.
I guess I can try this, even if I don’t have too many hopes…
Quick/dirty check with a waterfall spectrum after filtering out noise of of the linked .mp3
Time is on the vertical Axis (around 0.5 sec)
There is a faint constant periodic signal at just under 5kHz (around 13 pulses in 0.5 sec visible in the spectrum). And a louder “beep” at around 5.3kHz (sine wave visible in scope) halfway though the provided audio.
I have no idea what E/M radiation in that freq band could be around that’s picked up by your cable antenna.
Instead of running your guitar direct into your interface, try plugging it in to a DI box with a short cable (3’, 6’ at most) and run the DI box into the interface?
Does the beep come through and is it recorded, or is it just on playback/monitoring?
… and using a correctly terminated (microphone) balanced XLR cable can eliminate that antenna effect,
while left without termination (open) the XLR cable also will work as an antenna like all other unbalanced cables.
The input stages of the sound cards probably decode the low frequency part of the radiation signal → beep.
Just a wild guess.
As you move the cable around in various directions, will the beep be loader or quieter?
(takes some time to find out at 1 beep per 5 minutes.)
If so, that would give some hint of the direction where the signal is coming from.
My first suspicion is a cell phone tower near your building. Possibly some other RF transmitter, but cell phone would be the most common to be near a residential building.
Without knowing what kind of detector is in your phone and without a way to calibrate the levels there is no way to know if those measurements are useful at all.
If you notice the thread you linked to on thegearpage.net solved the problem by changing to less noise sensitive guitar pickups. You did not mention on either of these threads what type of pickups you have or any details about your guitar wiring (probably most relevant, what style shielding, if any, your guitar wiring cavity has).
My guess at the most efficient way to try to avoid the problem is to build a small RFI filter into the end of a cable, or in a small adapter at the audio interface input, but I have not seen a commercial offering of something like that, so would depend on your DIY soldering skills and willingness to experiment a little.
Unfortunately the time between the beeps is REALLY random, sometimes it was even longer than 5 minutes
Compatibly (as far as I know) with the idea of a signal intercepted by the cable acting as an antenna, it seems related to the length of the cable itself. I’m not hearing the beep with a shorter XLR cable (about 110 cm), but I’m still hearing the beep with a longer XLR cable or a longer jack cable (already since about 160 cm). Moreover I tried to crank up all the volumes on this headphone/portable amplifier I got and still no beep. The fact it is plugged directly into the guitar (so using no cable at all) makes me believe even more that this it is related to the length of the cable
I also tried this active DI BOX trying to follow @seablade advice but just plugging it in and using it “as it is” I’m still hearing the beep. Hower when I activate the “-20dB” attenuation switch on the DI BOX I’m not hearing the beep, at least until the time of writing.
As I could understand this switch just attenuates the signal, which seems to confirm my idea that the beep hearing is related to the high volume/gain of the signal, this is why I just turn everything up in my audio interface/monitors/heaphones to be able the beep more clearly.
I leave here the manual of the DI BOX for you to be able to get more information about the “-20dB” attenuation switches and/or on the DI BOX itself.
… and using a correctly terminated (microphone) balanced XLR cable can eliminate that antenna effect,
while left without termination (open) the XLR cable also will work as an antenna like all other unbalanced cables.
The input stages of the sound cards probably decode the low frequency part of the radiation signal → beep.
Just a wild guess.
I was making exactly your same guess. Anyway I’m not sure how to do the test you’re suggesting: should I just sit in front of the PC/audio interface as usual and rotate the jack plug not connected to the audio interface in any direction trying to see if the beep goes louder/quieter or I should walk through the room?
Actually that likely has more to do with that particular DI which I would toss in a trash can and set on fire if I were you. That DI is absolute garbage, I have had to use it and will do everything I can to never use it again. Injects lots of noise into the signal and it wouldn’t surprise me if it had shielding issues.
If you are getting it with an XLR cable, there is soemthing wrong. And by that I mean, part of what any decent DI box should do is take an unbalanced signal like what is coming out of your guitar that is subject to interference, and convert it to a balanced signal. Balanced signals, as long as properly wired and handled on both ends, are pretty damn resistant to interference. But you can’t just plug an XLR into a guitar and have it be a balanced signal. There is a way to wire a 1/4" TS to a XLR to plug the XLR into a balanced input to get the benefits of this, but it may not be the case that is what you are doing.
The fact that you didn’t get a beep when using a short cable of any sort means it is definitely noise injected in the cable (Provided that was the only variable you are changing) or connections. And as such I would look closely at your wiring.
I also assume this means you are hearing the beeps in any recording you do if the only variable you are changing to make it go away is the input cable?
Chances are if you are hearing it in nearby apartments, that won’t do you any good. It is likely being generated external to your building and not something you will be able to control in that case. You need to make sure your wiring is as good as you can, which means using as short unbalanced connections as possible, before converting them to balanced. Most DI boxes will have a ground lift switch as well, try that, which will lift the audio ground (Ideally with a 1:1 transformer), but maintain connection on the hot and cold to allow balanced signal to still pass. Most often used to fix ground loops which it doesn’t sound like that is what this is but may make a difference none the less, for instance if your M-Audio suffers from a Pin 1 problem and it is using the shield as an antenna if not connected properly.
Ok, so in this case it may be related to that bad DI BOX… Btw, it also has a “Groud Lift” switch which I tried too but nothing changed.
I also assume this means you are hearing the beeps in any recording you do if the only variable you are changing to make it go away is the input cable?
Yes, I can also ear the beep in my recordings
At this point may I ask you to recommend me a good DI BOX to use in my situation?
If I understood it correctly using a good DI BOX and connecting my guitar to it with a short - unbalanced - cable and then using a longer - balanced - XLR cable to connect the DI BOX to my audio interface I could solve the problem, did I get it right?
I was also wondering how long should the unbalanced and balanced cables be: for the standard 1/4" TS jack it should be 3 feet, 6 feet at most as you stated before? What about the balanced XLR cable instead?
I don’t think that DI is quite as bad as Seablade makes out, but it is active, meaning it has an op-amp buffer just like the input of the audio interfaces, which makes it just as susceptible to demodulating RFI.
The fact that two different audio interfaces and an active DI all expose the problem probably indicates more about the high level of RFI than about the quality of the devices. The Focusrite interfaces are pretty widely used, and I do not recall hearing other complaints of RFI sensitivity.
Did you also increase the gain at the audio interface by 20dB to keep the guitar level the same? RFI demodulation is very nonlinear, so reducing the input RF just a little can sometimes completely avoid the problem. It would not be optimal from a noise standpoint (white noise, i.e. hiss), but if attenuating in front of the first input stage and then making up the gain later avoids the buzzing and beeping, it might be worth extra hiss.
Hi there, thank you for answering.
Actually, as I wrote in the first message:
Musical Instruments doesn’t seem to be involved, as I can hear the beep just plugging one end of the jack into the audio interface and leave the other one unplugged
So it doesn’t seem I’d get something using the guitar type/manufacturer to investigate…
Actually, after the 20dB reduction I levelled the gain via software/audio interface knob to get a quite well audible signal.
So yes, white noise/hiss apart and - above all - as long as the beep doesn’t come out again maybe this can be a solution.
By the way, do you think using a passive box could improve the situation?
That isn’t a completely relevant test though, normally you would not have the unshielded plug just hanging out in the air. You can see the effect of that in your description of an unconnected microphone cable having the same noise, but as soon as you connect to a microphone, which connects a metal shell around the signal conductors, the noise is no longer heard.
You never did describe your guitar, but it is possible that a guitar with a well-shielded electronics cavity would not be susceptible to the same noise. Hard to say, because you almost always end up with holes in the shielding for the pickups to protrude through, which decreases the effectiveness considerably.
It is possible, but hard to guess in a general sense. Two different models of passive DI could have different behavior.
You mentioned that this also happens with an XLR cable if you’ve nothing connected to it. So might this be that your guitar requires a stereo jack cable but you’re using a mono cable? Or vice versa?
