Persistent interference in audio systems

[jwtp99]

Hi all, I posted this on HWZ and Xtremeplace (dead now) 5 years ago and never solved or found the source for this, thinking to try my luck again after half a decade:

I reported a whine/ringing/pinging sound from my turntable that is audible on the phono channel of my Onkyo amp. This sound is audible even if the turntable is powered off. This sound is not heard when the amplifier is switched to other channels (TV, Line-in, Aux, etc) and is only present on Phono.

The recording of the sound is here:



On both forums I have received PMs from users who reported having the same issue but are unable to fix it. Some have equipment worth thousands of dollars and they have to live with this same whining/ringing/pinging. I have also received messages saying it is present on their computer audio (speaker/microphones).

Also, I have heard this SAME noise when I put my ear beside my microwave (which has a tiny speaker for the beeps), and the SAME noise in my flat's elevator which has a speaker as well (I stay in a HDB BTO flat).

I have a portable turntable which can run on batteries or a DC adapter but I have always used it with batteries until I got a compatible DC adapter last week. When I plugged the DC adapter into this portable turntable, this dreaded sound is audible.

I have also recently restored a portable vintage cassette tape player which can run on batteries or a DC adapter. The same thing occurs; on batteries it is silent, but once I plug in a DC adapter, this dreaded sound is audible.

It is clear that it is interference of some sort, whether through the power mains or wirelessly, and it is quite widespread. As it doesn't occur when using devices with batteries I have reason to suspect it might not be wireless but I might be wrong.

I have been looking for an explanation, and/or the source for this for years but have never been successful.

Just thought I'd try my luck once more after 5 years: Has anyone experienced this before, or know where/what it might be?

Edit: Just searched on HWZ and someone posted the same sound:
https://forums.hardwarezone.com.sg/...itch-sound-in-logitech-z625-speakers.5965043/

so it is definitely a common thing in computers, PC speakers, turntables, cassette players, lifts, microwaves.. not only in one make or model of audio systems.

 

[wwenze]

Ah, I have this also. Common-mode noise on the AC mains. Usually worse at night.

In some situations, connecting the secondary ground to mains earth can solve the issue. However sometimes doing that will introduce another noise which can be louder so I choose the softer of the two.

Your amp will usually come with a ground terminal that you can experiment with. Either leave it unconnected, connected to the phono, or connected to mains earth (or both the phono and amp ground connected to mains earth) so you can see which is the quietest. The best solution however is to have a TT with a built in preamp or to use balanced connection.

 

[jwtp99]

Ah, I have this also. Common-mode noise on the AC mains. Usually worse at night.

In some situations, connecting the secondary ground to mains earth can solve the issue. However sometimes doing that will introduce another noise which can be louder so I choose the softer of the two.

Your amp will usually come with a ground terminal that you can experiment with. Either leave it unconnected, connected to the phono, or connected to mains earth (or both the phono and amp ground connected to mains earth) so you can see which is the quietest. The best solution however is to have a TT with a built in preamp or to use balanced connection.

I first only heard it from my Audio Technica turntable 5 years ago, but I have since heard it from my portable turntable (I have 2 and both have it) and cassette deck when using mains, so it is not an isolated case to one audio device.

The LP-120 has a built in preamp, and the noise was present. I physically removed the preamp and bypassed the connections and the noise is present. I used an external phono preamp and the noise is present. I would say I focused on the turntable initially because a turntable is highly sensitive and picks up the interference very easily.

I am unsure if it is common-mode noise. It is varying in pitch and volume, and also has pauses in between. I also hear it at all times of the day, but I can't say if it is worse at night.

I have grounded my turntable to the amplifier with the grounding post, and also grounded my turntable to the mains directly with no difference. Without connecting the ground the audio is un-listenable with excessive noise and distortion.

 

[wwenze]

So I'm assuming that your turntable is two pin power cable and your amp is also two pin power cable. (Or one of those that use those 3 pin power cable but on the amp there is only two pin.)

In that case, grounding the turntable to the amp is the best. It is usually done via the RCA but the extra ground wire also helps, although in most cases it won't make a difference.

For noise on AC line, you want to minimize the voltage difference between your amp and your turntable. Means no power conditioner between the amp and the filter. (Unfortunately most amps have some amount of power conditioning built in so this cannot be prevented completely.) The amp and turntable also be on the same power strip as close as possible. Finally you can try adding a power conditioner (or the more industrial name, a line filter) between the AC mains and the power strip containing both the amp and the turntable.

 

[jwtp99]

some more findings:



Bought a 'faraday' cloth which is basically a cloth made of fine metal mesh just to try and investigate further.

The whining is much less when holding the cloth at the rear of the turntable, and this is with the amplifier at full volume.

The cloth is not in contact with the turntable at the back, nor with the tonearm. I have turned off all other equipment except the amplifier (turntable is not powered but I understand the cartridge is 'live' through the phono jacks)

Putting the cloth around other parts of the turntable does not reduce the interference at all, only that specific corner of the turntable which faces the wall.

Looks to me to be EMI through the power lines in the wall.. or something to that extent.

I have heard this in friend's houses, mostly new HDBs.. I did not have this problem when I was previously living with my parents.. only from day one when I shifted to my own BTO.

I have previously posted this on Xtremeplace forum and had users message me about them spending hundreds on exotic sounding power conditioners and it did not fix the problem.. the answer is simply that this interference is not coming from the power line cable but is radiating wirelessly from the walls. This has been my suspicion all along for 5 years and I am just very curious to know what exactly is causing it.. hmm..

 

[wwenze]

For airborne EMI to radiate from the power line, the voltage has to exist on the power line to begin with.

The key is how u connect this voltage. If two points are at the same voltage, then there will be no field between them.

 

[benedium]

Last night my subwoofer suddenly got super loud. Not sure is it because it has been playing for hours or like wwenze said, cos of ac mains noise? I have it plugged directly into mains but now gonna plug into a multiplug extender. Hope that helps. Keeping fingers crossed.

 

[t258jgn]

maybe move your hifi away at least 2m from the wall sockets might help
Luckily I stay in old hdb where all wires are in surface trunking
My hifi nearest wall sockets are 2m

For turntable, some rca cables & rca plugs will pickup interference

I tried so many cables for my technics until I bought Atlas Element Achromatic Turntable Audio Cable
Solve my problem

 

[jwtp99]

Reviving this thread once more as I have found the cause of the issue some time ago and thought it would be a good closure for those facing the same issue:

The source of the interference is from the variable frequency drive coming from the lift/elevator in my HDB flat.

I can hear the same noise from the speaker in the lift (the one that announces the level, lift door opening/closing, etc) and the pitch of the whining changes exactly when the lift is in operation (high pitch when going up/down) and when stopping at a level (changes to lower pitch).

My unit was the nearest to the lift, but not directly facing it. The change in pitch of the interference is in sync with the movement of the lift, and since there are 2 lifts, the interference can vary in pitch quite a lot especially during peak periods when lots of people are going up and down.

I also tested my audio system at 2am when I verified the lifts have not been moving for a long time, and I could turn up my volume knob to the maximum with no interference. When the lifts are moving and I turn the volume knob to the maximum, the whining is loud enough for me to be concerned about blowing my speakers.

I have gone to other blocks in my HDB estate and noticed the same noise in every lift ('IFE' brand). I am unsure if it has anything to do with this brand specifically, or a specific type of variable frequency drive that they use.

I have used shielded RCA cables, I have lined the internals of my turntable with copper foil, and this audibly reduced the volume of the interference. I have ensured grounding is all properly done as well.

I have since shifted house to an old estate, and even though my unit is relatively near the lift ('Hitachi' brand), there is no longer any whining interference coming from my system anymore even when I turn the volume knob to the maximum.

Before I moved to my HDB I was staying in my parents home and I was using the same audio setup with no issues as well, it was only during the years I stayed at my BTO when this problem showed up.

To summarize, if you face this issue, it would be hard to fix as the interference affects a wide radius around the lift. The further you stay from the lift, the less likely you will face this issue. I am glad I have found the source of this after 6 years of troubleshooting.

 

[wizardofoz]

I went through a similar issue and can pick up the noise anywhere there is a power point in the house or at every single Power meter down every corridor too.

its a 5333Hz signal that intermittently comes and goes all the time. my hears it on speakers but I dont.

could be the lifts or maybe solar inverters perhaps...happened at my old block too

http:// walaneh.com/xpl/noise0002.wav

http:// walaneh.com/xpl/noisesound.wav

remove the space after the //

see the peak in the waveform analysis

 

[jwtp99]

see the peak in the waveform analysis

I listened to your recording, and that is exactly the noise I am hearing, and the changes in pitch and volume at varying times as well.. I am very sure it is coming from the lifts, and if you are able to test it in the dead of night when lift traffic is low I am quite confident you would not hear the ringing (buzzing would be due to grounding though).

I have posted a recording of the waveform before as well, with peaks at roughly 5300hz and 8000hz:

Some lifts would have it, some would not. The noise reduces but never completely goes away as shown in my video in earlier posts:

 

[wizardofoz]

My lifts are IFE I think... I think I found something about Ericsson Controllers using 5333Hz (5.333KHz) carrier frequency for controlling motors.

 

[Zesta92]

I am having the same issue as you - resale hdb

Logitech computer speakers is the more obvious noise throughout the day
Computer PSU affected too
Fridge does have the same sound just more subtle due to wider living room/tv and usually only hear it at wee hours

Interference issue happened to me after my lifts got upgraded and have contacted town council
So far only when lifts are in motion then the high pitch noise will show up

Currently in talks with town council but not gaining traction

 

[aviator27]

Just wanted to share how I managed to solve this noise issue. I bought a balanced isolation transformer and use it to power my turntable. The noise is no longer there.
I bought the same one as this

https://www.aliexpress.com/item/329...2ODc4MzckbzMkZzEkdDE3NjI2ODc4NjIkajM1JGwwJGgw

It is also available from TaoBao