Occasionally, when listening to my system (through speakers or headphones) I get a short burst of a humming noise.

How do I find out what the source of this noise is, and more importantly, how do I get rid of it?

I will be checking to see if it is source dependent later today, as I noticed it yesterday when listening to vinyl.

At a guess, I would say it is probably in the 50Hz range, but it could be a multiple of 50Hz. It usually lasts for about 2 or 3 seconds.

There are two types of mains frequency noise: 1. 50Hz hum; 2. 100Hz buzz. In addition there is interference noise from TV and monitor screens which may have LCD (or similar) excitation frequencies, sometimes 75Hz.

There can be contact noise where a connection is on its last legs, thus removing the shielding function intermittently, resulting in "mains hum".

As you only recently noticed it ("as I noticed it yesterday when listening to vinyl"), then is there anything that has changed recently, or any new household electronics or electricals?

Plug-in lamp dimmers on the same ring as hifi can induce noise.

It is not new, but yesterday on headphone listening it was there.

I had heard it before using my speakers, but was surprised to hear it yesterday.

I think I would go for option 2. 100Hz buzz.

Nothing has changed recently, but I know I have noisy mains, as we have a smart meter, power line network adapters, air conditioning and a heat pump.

So if there is nothing I can do to filter it out, I guess I will have to live with it.

Thanks. I don’t have ring circuits. My HiFi is on a dedicated line, but it all feeds back to the same place….

Not a case of living with it. More like an ongoing investigation.

I and others can only give examples. Here's another.

I had an Hadcock GH 228 unipivot arm and upgraded to a GH 242.

Rather than being quiet, the new arm would introduce mains hum/buzz every now and then.

This was because the arm tube metal wasn't making electrical contact with the arm base, because the unipivot wasn't pressing "hard enough" together to always cause an electrical contact. Otherwise, the unipivot was doing its job as a bearing.

As such, the arm tube surrounding the arm wires wasn't an effective sheild, and then it was, and then it wasn't.

Eventually I said sod it and bought a fuss-free Technics.

We can only give you our stories in the hope something clicks (or doesn't...).

Hi Richard, I think he's got one of those in his power amp.

Thanks Rich, unfortunately it is not transformer buzz. I built and fitted a DC blocker into my amplifier.

The buzz can be heard through the speakers/headphones and only lasts 1 or 2 seconds, so could be a fridge or something else turning on/off.

I can't imagine you haven't considered mobile phone interference. I have occasionally noticed intrusions from my phone a it keeps "in touch" with the network. Most often when the local mast is not available due to reaching max capacity or maintenance and the phone has to increase signal strength.

Just a thought.

Ian

Possibilities:

You are correct, but I don't want to turn any of those off!

Having a fridge/freezer, a fridge and a freezer in the house makes this a challenge.

Soon I can see if it is the heat pump, as I will be able to turn the heating off soon - hopefully!

Thanks. Luckily I can’t hear it when the music is playing, but I know it is there.

I am in the lucky position of having several well designed phonostages “available” to swap in to see if it is the phonostage.

It is either a ferrite I have put on a power cable, or the network cable I moved to put the ferrite on the cable.

I have not heard the buzz for about 10 minutes, which is unusual….

Fingers crossed.

It is fixed though, so I am happy. I was wearing my headphones as I fitted the ferrites on various cables. No difference was audible until I clipped one around the cable that feeds my power block. The pitch of the buzz increased slightly, and then went silent. It has not been back since, and I have moved the network cable back to where it was.

I can’t explain why it is fixed….

Well done, Kevin!

Neither can I explain exactly why it is fixed.

But I do know that RF (frequencies that are in the radio spectrum that aren't always due to TV or radio transmission), will trigger oscillations at the strongest local frequency (this being the ever present mains), in components operating close to "the edge".

That "edge" is constantly changing due to a thing called "progress", so can happen to any sensitive analogue circuit. Progress disregards the playing of records. In other words, record playing equipment is rather inconvenient for progress, and "they" never thought vinyl would make a comeback as it did. So it has become a no man's land regarding "the standards", because "they" know they are also unable to work it out. Therefore, it can always be blamed on the equipment manufacturer, or the user - anybody but "they".

There'd have been exactly the same problems with live performance, had it not been for forward thinking, and a thing called the hearing loop, which made the dynamic mic a thing of the past. They too, as well as mixer input stages, pick up all the airborne crapito. So now they're condenser which is non-magnetic. Additionally, they contain a preamp right there at the source.

Another thing about the microphone is that it is fully shielded - even where the sound passes through is a Faraday cage.

With record players however, outputs of a millivolt or so from a magnetic cartridge (with its seriously non-linear output increasing at +6dB per octave) ARE NOT SHIELDED. The industry refuses to adapt with the progress, although it can easily do so, but has its head firmly planted where the sun don't shine. It is at record players that the standards writers give up the ghost. A kind of "let the children play" attitude, hoping that its generations will pass away one day and take their record players with them.

So, some acceptable modern interference happens somewhere, which can be just about anywhere, and that triggers a sequence of events resulting in spurious oscillations. And then it's "find the needle in the haystack" time.

A ferrite on a cable makes a "half turn transformer" such that the frequency the ferrite becomes lossy at, is short circuited to itself, and does what all ouslem birds do. The frequency will be well into RF, and not mains frequency, but remember, it's the trigger.

If it was not the cable, I was going to put a properly built phono stage in the system to eliminate the "DIY" model I have, but fortunately, I did not have to do that yet.

My "Smart Meter" let the magic smoke escape last night/this morning.

So I am patiently waiting for a replacement meter. It could be related to the noise I have heard recently.

I will remove the ferrites from the power cable when the new one is fitted, and see if there is any hum/buzz with the new meter.

The "owner" of the meter tells me I need to put some product in the meter box to stop the ants. 

I reminded him that neither the meter, or the box belong to me, nor are they on my property, and as I don't have a key, how can I, even if I wanted to?

The conversation was cut short as they found a problem with the installation.....

Result? No hum/buzz audible on the vinyl side of my system.

I would never have found that fault, so I am happy it has been replaced

I dug out my old mains regenerator and have plugged everything but the power amp into it.

The result is that silence has now returned, and hopefully the hum/buzz is banished from my system.

As soon as my phono stage is turned on in my system, the buzz of the AG1500 stops, but there is a very faint noise audible through my headphones/speakers.

I plugged in my Amazon Commercial “Pure Sine Wave” 1500VA UPS (which is usually used for my NAS) and the unit does not buzz. Neither do I have the occasional hum/buzz through the headphones/speakers. Is a cheap UPS (SMPS based?) really the solution?

I do not want to spend thousands on a HiFi mains conditioner.

I would rather have the occasional buzz.

So what would one of those achieve?

The filtered IEC inlets arrived today. So I took my extension block apart only to find that I could not fit the IEC inlet, as there is a metal shield running down the middle of the enclosure.

So I put it back together, making sure all of the screws for the cables were tight. I then plugged everything back in, but in a different order (against the manufacturers recommendations). I also reorientated the mains block in an attempt to dress my cables.

I have yet to hear the buzz tonight. I don’t want to tempt fate just yet…

So my system is plugged in to the mains, with the exception of the phono stage.

The system is now silent, but I want to get rid of the AG1500 power regenerator, as I know this is throwing noise back into the mains.

Every time I think I have fixed the issue after a few hours of silence, it comes back.

It does sound a bit like a ground loop hum, that lasts for maybe one to two seconds.

I tried an iFi iPurifier. It did nothing, so got sent back.

I have some more ferrites on my phono leads between TT and phono stage. The occasional buzz has reduced in intensity, but it is still there.

Only one cable left in the analogue chain to treat now. The earth cable between TT and phono stage.

I guess it is just like an aerial, just sitting there to pick up RFI. It is quite thin, so I may have to wrap it around a ferrite.

I fitted a ferrite bead to my TT earth wire last night, (it was a spare one from my mains cable beads, so is massive)  and there is a very slight trace of a buzz now.

I think I need an RFI/EMI resistant earth lead, and I can finally point this subject to bed.

It has been an interesting journey so far, which is almost finished, I hope. Now I just need to work out how to make this lead.

So a shielded ground cable, eh?

Where are you going to ground the shield to..........?

But how do I stop it from being an aerial?

I think there is a mobile phone mast about 1km away. This could be the source.

I am going to try a couple of ferrites (of the correct size) first, and then look at other options.

I may try removing the lead altogether, but so far, ferrites seem to be the answer.

Hook it up to there.

You posted before I finished typing.

Something else crossed my mind.

Are you still using AK's modified arm, and what is the arm tube made of?

Yes, I have AKs modified arm, with an aluminium arm tube. 

I have just made a new grounding lead, with a floating shield. It has been plugged in for 15 minutes, and no signs of a hum. It may not be the theoretically optimal solution, but if it works, who cares?

Why did I not think of this earlier?

Why, because it still hums…. 

Digital is so much easier.

Out of desperation, I fitted ferrite beads on the internal power cables inside my phono stage, and the noise has dropped dramatically. I am hard pushed to hear it at normal listening levels (without music playing) so I have bought an Isotek power filter to see if that will help.

Is it worth swapping out your "lockdown special" valve hybrid phono stage and reinstating your previous solid state phono? 

As a valve unit, there is inherently more mains related guff floating about (heater, higher dc supply) in it.

I don’t own a SS phono stage. I do have plenty available, but they are not mine. 

I am determined to fix the issue. I am a bit stubborn about these things. Hopefully it will be fixed at the weekend.

I have plugged in it to my system, feeding my phono stage and preamp. So far, so good. The system has been powered up for over an hour, and no sign of the Buzz.

If this is what it takes to get rid of the noise (and hopefully have a better signal due to the lack of the noise) then it will be money well spent. I am sure I could probably build something cheaper, but this was much easier.

The system almost seems to send more details, due to the lack of noise.

It has a very bright blue LED built in it though.

If you listen (amongst the hiss) to this clip, you can possibly hear it. -  https://drive.google.com/file/d/11W048At3m5d7KcalhMxty-9un6VDKxOY/view?usp=share_link - https://drive.google.com/file/d/11W048At3m5d7KcalhMxty-9un6VDKxOY/view?usp=share_link

This is a condensed 3 minute clip, so you can see that the hum is not constant, but it almost sounds like a harmonic of 50Hz to my untrained ears.

I have a temporary fix, using my mains regenerator gets rid of it completely, but I would still like to know what is causing this, so I can fix the issue.

https://drive.google.com/file/d/1BussEKjYFLIOfFVnNHTQ5qxh0FekSQo1/view?usp=sharing - https://drive.google.com/file/d/1BussEKjYFLIOfFVnNHTQ5qxh0FekSQo1/view?usp=sharing

There is a noise at 50Hz and a bigger one at 100Hz.

I guess I don't have many option of filtering this 100Hz noise out?

It makes me wonder if this is ground loop related, and if so would a mains isolation transformer help?

It seems that it was either an earth loop, or loop pick up.

It is not perfect, but I will do a better job in the Christmas holidays.

Glad to know that you're getting somewhere near solving the problem. Earth loops/pickup can be so difficult to isolate. I find that turntables are the worst culprit, earthing arrangements can be so haphazard, or even non existant.

Happy Listening

Ian

I have not had the faintest sign of the hum.

I think I can put this subject to bed, and move on.