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Electrical interference from speakers with no audio connection
Old 9th October 2019
  #1
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Electrical interference from speakers with no audio connection

Hey!

I'm having trouble with interference that I think is coming from the mains. The noise is a high pitched whine that sounds like it's distorted and is very painful. I've attached a clip of the sound - I think the lower frequency white noise is normal but the high pitched whine is not?

I moved into a new apartment about a year ago. 3 months after moving in, I bought an amp/speakers from goodwill. The amp was causing random crackling/popping at times but that went away with use. I use them as part of a dj setup. Everything was great for a couple of months. I used the equipment nearly every day.

One day after practicing djing for about an hour, I found that my ears physically hurt and I had a headache. I thought I maybe had the volume too loud but it started happening every time I play music. I noticed that there was a new distorted high pitch whine coming from my speakers that was not there before. It sounded like all my music was clipping despite the levels being ok.

After trouble shooting my equpiment, I concluded that the sound was caused by my amp/speakers and not any other equipment. I assumed the used equipment must have died, so I bought a new set of active monitors (monoprice 8inch). However, the issue persisted with the new speakers!

This prompted me to do a lot more troubleshooting. I tried every socket in my apartment and turning off breakers (and all battery powered devices such as laptop/phone) but nothing helped. I told my landlord who let me test in the apartment downstairs (there are only 2 apartments in my building). Same issue (although I didn't turn off the breakers down there). My landlord had an electrician come and look at it. He said he doesn't know anything about audio and could only really check the ground, which was fine.

I know that I have phone towers nearby and have tried using baking sheets to block the signal but that didn't seem to do anything.

After all that I returned the monoprice speakers because they hadn't helped. I tried a 31 mix ferrite choke (AC power Speaker buzz with no audio connections) around the power cable to the amp as well as the actual speaker cables but it didn't help regardless of the number of turns.

At this point I am out of ideas. I do think that it's possible to block this noise somehow because I have 2 dj mixers. The cheaper one has the noise in the headphone channel but the fancier one does not. I'm just not sure what else to try.

tl;dr
  • painful high pitch whine in speakers
  • noise present with no audio cables connected
  • not caused by any electric devices in the apartment
  • downstairs apartment has same issue
  • premium dj mixer filters the noise in headphone channel, budget mixer does not
  • electrician has checked ground which is fine
  • new speakers (monoprice 8inch monitors) did not help
  • mix 31 ferrite choke has no affect
Attached Files

2019_10_08_16_12_12.mp3 (90.3 KB, 373 views)

Old 9th October 2019
  #2
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Radardoug's Avatar
 

Theres nothing weird on your clip, it just sounds like room noise. Maybe you have a hearing problem?
Old 9th October 2019
  #3
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I have considered that it could be my hearing but ruled it out because I don't get the pain when listening to battery powered devices (my phone, for example). I will probably have my hearing tested just in case
Old 9th October 2019
  #4
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Not saying you have tinnitus, but FWIW here's a quick way for some self-screening:

Turn on the speakers (or whatever you suspect is causing noise). Stand about 6' from them. Listen for the whine.

Turn your head, slowly, 90 degrees in each direction. Move your head from side to side slowly, maybe 6" in each direction.

Does the noise change while you're turning or moving? Then it's probably acoustic.
Does the noise stay steady? Suspect your hearing.

High frequencies are -very- directional. They can bounce around the room, causing reinforcements and cancellations at different spots in the room. If the room doesn't have any reflections, you'll hear directional beaming.
Old 9th October 2019
  #5
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samwinston123's Avatar
 

I hear a tone around 4kHz although it's very faint. That's a recording of the speakers with nothing plugged into them? The cheap mixer has the same noise in the headphones with nothing plugged into it?

When you say that all the music sounds distorted, that makes me think that something is oscillating at a very high frequency which is reducing the headroom available for the audible frequencies.
Old 9th October 2019
  #6
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Jay Rose, thanks for your suggestion! I did the test but it's hard to tell because the whining noise is not a consistent tone, even when I'm stationary. I don't know that much about tinnitus but my only experience with it has been ringing in the ears. Maybe there are other symptoms but the noise is definitely not a ringing in my ears. I know that because the whining noise actually causes me tinnitus after listening for more than 5-10 minutes

samwinston123, thanks for your input! That is indeed a recording of the speakers with nothing plugged in (only power). The cheap mixer has that sound in the headphones with no audio signals plugged in. You say that you hear a tone around 4kHz but what I'm hearing seems much higher to me, closer to the borderline of my hearing range (not that I'm good at estimating frequency range). I think my audio sample is throwing people off because it contains 'normal' speaker hum and also this whining noise. I will try to use a high pass filter to make the whining noise clearer. The sound is not a consistent tone, it is something that gets louder and quieter, which could align with your oscillating theory. What could cause something like that?
Old 9th October 2019
  #7
Led
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Led's Avatar
I hear the same thing Sam mentioned. could be a fan whining?
Old 4 weeks ago
  #8
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I think I may have had a window open during my first recording and that is road noise you are hearing. I have recorded another demo that I think more clearly captures the issue. I didn't use a high pass filter, just turned down the bass on the amp and held my phone closer to the tweeter while recording
Attached Files

2019_10_09_16_01_11.mp3 (438.1 KB, 300 views)

Old 4 weeks ago
  #9
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Radardoug's Avatar
 

Heres a spectrum of one of the loud pulses. I would say its computer related. Might even be your phone.
Attached Thumbnails
Electrical interference from speakers with no audio connection-noisespectrum.jpg  
Old 4 weeks ago
  #10
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Radardoug, I have no idea how to read that chart but truly appreciate you looking into this! Are you saying the speakers could be picking up interference from the air and not the mains? I have tested this in the past with my phone and laptop turned off, so I can rule them out. I know that I have 2 satellite dishes on my building just outside my window and also cell phone repeaters within 100m - I've tried to block them out with baking sheets in the past but didn't have much luck (I don't even know if a baking sheet would block those signals tbh)
Old 4 weeks ago
  #11
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S_mask's Avatar
 

There's a sort of spikette at 2 kHz, and a series of spikes starting at 4 kHz, repeating each 2 kHz, at 6 kHz, 8 kHz, 10 kHz, and 12 kHz.

It goes away and returns, too.

A screen shot of the FFT in SpectraFoo responding to your file's playback is attached.
Attached Thumbnails
Electrical interference from speakers with no audio connection-speaker_spikes.jpg  
Old 4 weeks ago
  #12
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samwinston123's Avatar
 

Yeah those noises in the second recording are some kind of wireless signal modulation.

The baking sheets will only work if you ground them somehow. Otherwise they just turn into crude repeaters. Are these speakers active or passive?
Old 4 weeks ago
  #13
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S_mask, thanks for that FFT - it gives good insight as to exactly what I'm hearing! I learnt what FFT is too

samwinston123, that's great to hear they are from wireless! That explains a lot. I had a hunch at some point but thought I had ruled it out with my baking sheet idea. For future reference, how can you tell that it's wireless interference? Is it the specific frequencies from the FFT or something else?

The current speakers are passive. Is it important to shield the speakers or the amp? I guess I will perform the baking sheet test again but use a crocodile clip to ground the baking sheet to my mixer. The baking sheets are aluminum - is that a good material to use?

As I mentioned in the op, I did buy active monitors at one point when I thought this was caused by broken speakers. Those speakers still had the noise and when I plugged in the audio cables (xlr) it actually made the issue worse. It sounds like that can be explained by the interference being wireless and the xlr cables acting as antenna's?
Old 4 weeks ago
  #14
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S_mask's Avatar
 

A similar-seeming issue is discussed in this thread

10khz noise in speakers

The solution was a 3 kW isolation transformer. (A(n) UPS worked, too).
Old 4 weeks ago
  #15
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Thanks! I'll read through that thread. I've seen another similar issue posted here which is what lead me to this forum but haven't seen the one you posted before.

I also used my aluminum baking sheet grounded to my mixer to try and block the interference but it didn't seem to have much effect. I only tried it on one of the speakers, though, maybe I need to also consider the amp and speaker cable?
Old 4 weeks ago
  #16
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samwinston123's Avatar
 

Quote:
Originally Posted by lpww View Post
S_mask, thanks for that FFT - it gives good insight as to exactly what I'm hearing! I learnt what FFT is too

samwinston123, that's great to hear they are from wireless! That explains a lot. I had a hunch at some point but thought I had ruled it out with my baking sheet idea. For future reference, how can you tell that it's wireless interference? Is it the specific frequencies from the FFT or something else?

The current speakers are passive. Is it important to shield the speakers or the amp? I guess I will perform the baking sheet test again but use a crocodile clip to ground the baking sheet to my mixer. The baking sheets are aluminum - is that a good material to use?

As I mentioned in the op, I did buy active monitors at one point when I thought this was caused by broken speakers. Those speakers still had the noise and when I plugged in the audio cables (xlr) it actually made the issue worse. It sounds like that can be explained by the interference being wireless and the xlr cables acting as antenna's?
I can’t say that it’s *definitely* wireless but that’s what it sounds like. You’ll hear similar noises if you put your phone near poorly shielded equipment.

The amp is where the shielding is crucial, a speaker on its own is generally not susceptible to this kind of interference because it’s very low impedance.

What’s the make/model of your amp?
Old 4 weeks ago
  #17
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Quote:
Originally Posted by samwinston123 View Post
I can’t say that it’s *definitely* wireless but that’s what it sounds like. You’ll hear similar noises if you put your phone near poorly shielded equipment.

The amp is where the shielding is crucial, a speaker on its own is generally not susceptible to this kind of interference because it’s very low impedance.

What’s the make/model of your amp?
I guess I've been focused too much on the speakers but you're right that the amp seems to be picking up the interference. My amp is a Quadraflex Reference 180R. It has an AM/FM tuner. I can dramatically reduce the interference by just putting my hands around the ariel!

Do I need a new amp or can I shield my system? If I can shield it, what's the best way? Also, would you expect a ferrite to help with this issue because mine did nothing but I thought this is what it's supposed to solve?
Old 4 weeks ago
  #18
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samwinston123's Avatar
 

Quote:
Originally Posted by lpww View Post
I guess I've been focused too much on the speakers but you're right that the amp seems to be picking up the interference. My amp is a Quadraflex Reference 180R. It has an AM/FM tuner. I can dramatically reduce the interference by just putting my hands around the ariel!

Do I need a new amp or can I shield my system? If I can shield it, what's the best way? Also, would you expect a ferrite to help with this issue because mine did nothing but I thought this is what it's supposed to solve?
The grounding situation is a little weird with a vintage consumer receiver like that one. It has a two prong plug so the chassis isn't directly connected to earth/ground. There's a nut on the back labeled Ground or Gnd, that's for connecting the chassis to earth. You need to run a wire from that nut to the case of something else that does have a 3 prong plug. Maybe your DJ mixer?
Old 4 weeks ago
  #19
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Quote:
Originally Posted by samwinston123 View Post
The grounding situation is a little weird with a vintage consumer receiver like that one. It has a two prong plug so the chassis isn't directly connected to earth/ground. There's a nut on the back labeled Ground or Gnd, that's for connecting the chassis to earth. You need to run a wire from that nut to the case of something else that does have a 3 prong plug. Maybe your DJ mixer?
Thanks Sam. You are correct that my receiver has a 2 prong plug but connecting the ground to my mixer doesn't seem to effect anything. I don't think it's a grounding issue though because the brand new active monitors (monoprice 8inch) that I bought still picked up the noise with no audio connected.

Any idea how I can shield the amp from the wireless interference that it seems to be picking up? I tried tin foil but it wasn't very effective
Old 3 weeks ago
  #20
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audiospecific's Avatar
 

Maybe they used the incorrect way of installing the wiring connected to the outlet. Remove the wall plate and look to see if they just stabbed the wires in the back of the outlet (incorrect way) instead of using screw terminals on the outlet (correct way)
Old 3 weeks ago
  #21
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audiospecific's Avatar
 

Btw a faulty gcfi circuit can throw noise on the line like that too.
Old 3 weeks ago
  #22
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Thanks! I will take that into consideration. Can the GFCI outlet still cause problems if it's turned off at the fusebox?
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