View Full Version : Occasional hum
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.
I am thinking of fitting a filtered IEC to my mains block as a first step, as I think it is noise on the mains. Any other suggestions?
lighting or fridge are the usual culprits.
Wakefield Turntables
07-03-2023, 07:13
This does sometimes happen to me when our bathroom lighting goes on.
lighting or fridge are the usual culprits.
It could be worse than that, as I have a fridge freezer, a fridge and a freezer, two air conditioning units and a heat pump, so I guess either of these could be causing it?
And it it is mains noise, I understand there is no way to filter it, as I would have no mains….
fit a separate spur for the hi fi maybe. if its new then have you fitted any new electrical stuff lately?
Thanks Grant. I already have a separate spur, as there are no ring mains in France.
There is also a “Linky” Smart meter in just about every house that will also add noise to the mains.
It may be more apparent in the evening when the LED lights are on, and the heating is working more. I shall investigate further, but this may just be something I have to live with.
It is not new, but it is starting to annoy me more. It has been colder recently, so it may well be heat pump related.
could be the led lights. they are switch mode..
Anyway to get rid of it then?
I am surrounded by SMPS and variable frequency compressors.
I have an old AG1500 (that has a mechanical buzz) that I could fit to see if it fixes the mains noise.
guess if you go through all the smps one by one you might find the one thats causing it. if its new then it may be last one fitted(but alas not nesessarily lol). not easy sometimes to trace it. it takes patience and time unless you get lucky... might never find it tho, and its something you never thought of sadly..
If it is the heating, I have to live with it.
i guess so.. still might be worth a trial, say with different things off etc.
I am listening to the system (with no music playing) as I work, and there is much less hum now than there was last night.
During the day, I will turn lights on etc. And see if I can find the culprit.
is this a constant noise then? I thought it was intermittent?
Nope. It comes and goes. Lasts around 2 seconds.
Sounds like something switching on and off on the ring main?
If only I had a ring main... ;)
The heat pump is a full inverter, so it could be this, as they are noisy.
Is there a filter that stops noise from Fridges/Freezers going back into the mains?
Will ferrites be of any help?
You could try ferrite rings/tubes on the SMPS; although most have one fitted already.
Regarding ring mains: they are no help in suppressing switching spikes - in fact in this respect the spur system is better, as the increased resistance of the path between the source of the spike and the recipient is longer (it has to go back to the meter and then back out again to your audio gear), and hence helps to suppress the spike.
New discovery tonight - It is only on the analogue side of my system, so not likely to be a mains issue?
Makes me wonder if it is RFI or EMI now.
The digital side uses USB/coax into an Audio GD DI2014, which feeds the DAC via another coax cable. Connections between the DAC, Preamp and amplifier are all balanced.
On the analogue side, I use coax interconnects cables from SL1200 into the BB3, core for signal and shield as return, and a “balanced” RCA cable with the screen connected at the source end only, going from BB3 to Pre.
I think my money is on the last cable being the problem child.
Having listened to a few sound effects on YouTube, it sounds a bit like a short 5G signal.
get some ferrites, if it's RFI that should sort it.
Ferrites are arriving in the next few hours. :thumbsup:
maybe they just put up a mast near to you?
I also swapped the “balanced” cable out for another coax. No real change.
maybe they just put up a mast near to you?
It is a possibility. I am hoping the ferrites are the magic cure.
cheap and simple solution if so.
Although if your life is anything like mine cheap and simple solutions are pretty rare events.
you might get lucky with ferites. i used them once and they helped a bit but didnt solve it completely.
will say ive had hum issues with cables and sometimes it can and sometimes it cant be easily solved
It is not a loud hum, but it annoys me that it is there.
I will try ferrites, and also a different phono stage. I can also try a different cable between the SL1200 and the BB3 to see if this is the culprit.
tonearm cable too it's carrying the weakest signal.
I have 5 pairs arriving. Should be here soon..
At least I know it is not the mains.
I think I have found the culprit.
It may be a network cable which I quickly threw behind the furniture when my wifi stopped working mid meeting.
Either that or a ferrite I put on a power cable.
Not heard the buzz for a while.
Weekend job is to dress the cables as best as possible.
There has been an interesting twist to this tale.
The “smart meter” feeding my house had been invaded by ants, which caused a problem.
This was replaced, only to find a dodgy connector on the telegraph pole connector. This has just been sorted.
The outcome? No hum/Buzz, and I am almost at the point of believing that my system sounds better today than it has for the last few days.
True…
I have to say that they were very efficient in sorting the problem. Less than 10 hours to reporting the issue to it being fixed.
I don’t think I have ever heard of that happening in the U.K.? :ner:
It seems I wasted €10 on ferrites, but I am glad I did not buy one of the mains regenerators I looked at.
True…
I have to say that they were very efficient in sorting the problem. Less than 10 hours to reporting the issue to it being fixed.
I don’t think I have ever heard of that happening in the U.K.? :ner:
It seems I wasted €10 on ferrites, but I am glad I did not buy one of the mains regenerators I looked at.
i have a regenerator and it does work well. or did when i used it... not sure where it is now tho..lol
I have it’s bigger brother, but it started to make a whining noise.
I have it’s bigger brother, but it started to make a whining noise.
thats sad... ive never had that with mine. always been pretty quiet. heavy and an awkward size alas
As posted elsewhere, mine no longer makes any noise.
The hum/buzz came back at a lower level last night, so thanks to Grant's reminder, I have plugged the AG1500 back into my system.
Silence is golden.
I just need to find the feet for it now, as it is now stood on end next to my rack, and I don't want it falling over.
As posted elsewhere, mine no longer makes any noise.
The hum/buzz came back at a lower level last night, so thanks to Grant's reminder, I have plugged the AG1500 back into my system.
Silence is golden.
I just need to find the feet for it now, as it is now stood on end next to my rack, and I don't want it falling over.
You check to see if the ants are back? Might need to get the Deathlac out again :)
Having no electricity is a bit of an inconvenience so I gave an “ant box” to the guys who changed the meter to put in the meter box. I didn’t want a “smart meter” and there was nothing wrong with the old one. However, it makes it easier for the electricity companies to collect the data and bill us. They also inject more noise on the mains, and every house has one.
I have found my feet. The AG1500 can stay.
With the phono stage, pre and headphone amp running, it is at 0% load, apparently.
The fans are silent. I have no hum.
I have found my feet. The AG1500 can stay.
With the phono stage, pre and headphone amp running, it is at 0% load, apparently.
The fans are silent. I have no hum.
i always used mine on its side as the display rotated. it was at side tho and never fell over
Is the software worth installing on my PC?
I never did, so I am wondering if it adds any benefit.
I may have finally fixed this issue.
If I hear no buzz in my listening session tonight, I will update this post.
I may have finally fixed this issue.
If I hear no buzz in my listening session tonight, I will update this post.
be good to hear what it was
I didn’t update the post. It came back, which makes me think it is something external to the house causing the problem.
The AG1500 fixes it, but that is noisy, so I am going to make a temporary mains filter to see if that will do the job, before I invest more money chasing this noise.
Has anybody tried one of these? https://www.atlhifi.com/shop/fully-assembled-devices/combined-module-dc-blocker-emi-rfi-common-mode-filter-assembled-in-case/
This may be what I need for the “buzz”.
That or an isolation transformer?
The family has gone out. I am alone.
I have plugged the UPS back in with the power amp fed from the mains.
It sounds fine, but there is a buzz.
might need to try and emulate house power usage that would be typical in evening.
It buzzed not matter what time of day it is, so it has to be the heat pump, fridge/freezer or power line network adapters.
I think there is some sort of suppressor you can get to plug your fridge into but I don't know what they are called.
Better to do it that way and fix at source rather than put a band aid on the system.
fridges etc usually give a click, not a hum
It could be the heat pump then. I will found out when summer comes, and the heating goes off.
fridges etc usually give a click, not a hum
Good point.
Do you think something like this https://www.atlhifi.com/shop/fully-assembled-devices/combined-module-dc-blocker-emi-rfi-common-mode-filter-assembled-in-case/ would do the trick?
looks well enough made and might work, but it is hit and miss as you still haven't isolated the issue yet kevin, and its not cheap.
your probably as well waiting until the heating is not getting much use and see if the hm is not as often. if thats case then you at least have to culprit. its always better treating the source rather than trying to block it after
There is no way I can change the heating. ;)
I am going to go and turn it off now the family has gone to bed and see if that is the culprit.
It is not the heating, so I have noise on the mains. It is not DC. It is not the power line network adapters.
I don’t think I will ever find out what it is.
Ground loop? Faulty equipment?
Ground loop? Faulty equipment?
More than likely - easily achieved with the usual (un-balanced) connectivity.
So how does the AG1500 fix the ground loop/faulty equipment?
The system is silent with the mains regenerator in place, which is more than can be said for the AG1500.
So how does the AG1500 fix the ground loop/faulty equipment?
The system is silent with the mains regenerator in place, which is more than can be said for the AG1500.
from what I can gather (and I don't really understand this) the transformer will suppress the mains components causing the hum but does not actually eliminate the ground loop.
you could try a band-stop filter...
https://en.wikipedia.org/wiki/Band-stop_filter
Thanks Grant. That looks interesting.
I think I have a temporary fix. I connect just the BB3 to the AG1500, so it is silent when I listen to vinyl.
This removes the occasional hum/buzz.
Edited to add:
I have a temporary fix, as what ever is causing the noise is not something I can turn off.
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
Can a ground loop be intermittent?
yup they can, especially if some big electrical unit is kicking in and altering the earth system. transformers will mask the issue but wont solve it obviously. being a french power system too may make it more difficult to track for non french if you know what i mean.
maybe a better mains tx system might be your best bet?
I have ordered an iFi AC Purifier to see what that does, and if it has a negative effect, I will send it back.
An isolation transformer could be a solution, but if this is a ground issue, I need to find it.
My concern is that this is due to all the smart meters that send data to EDF on the power network. Filters do exist, but they are relatively expensive.
I guess I need to trawl some French Hifi fora.
The only leads I have not swapped out in my system are TT to Phono.
I may try these tonight, but I still think it is mains related.
phono leads especially and phono stages can produce hum, often fields from power cables etc.
I think I may have cracked this. At long last, I hear you say.
My system has been on for an hour since I changed something. Before the change, I heard the buzz. Since the change, so far so good.
The culprit? A while ago I plugged a generic USB lead from my PC to my DAC, so I could do a direct comparison with and with out my Audio-GD DI2014 in the system. I left it plugged in, as I was lazy, and what harm could it do? I have removed that USB lead, and all I can hear now is a bit of valve hiss. No more Buzz every now and again….
I am (really) hoping this is my last post on this subject, but thought it may be useful to share my findings.
I guess I don’t need the iFi purifier now.
phono leads especially and phono stages can produce hum, often fields from power cables etc.
That is why I made some using a good quality coax cable, as advised by a respected phono stage designer.
you do get current spikes in the USB cable. The USB cable has resistance, a small voltage is induced between the USB audio device and ground at the other end of the USB cable. This isnt much, but devices like phonos only generate a few thousandths of a volt, so it's plenty of signal to cause havoc if it gets back into the preamps.
good youve got culprit...
I was just reading the other day about USB creating ground loops but I didn't think you were using one.
I forgot it was still plugged in, to be honest. I do have one going from my PC to the DI, but that is fine.
It turns out that the USB cable was not the culprit, even though I thought it was.
So, I bought an iFi iPurifier for the mains. It did nothing so I sent it back.
Next up are some ferrite chokes on the SE cables. So far, so good, but I need some more time listening.
It may still be there, but at a much lower level, which may be acceptable.
You need one of these Kevin, it will probably cure all your noise problems. I heard one here the other day it was totally gobsmacking but so is the price!:eek:
https://www.futureshop.co.uk/chord-poweraray-professional-noise-reduction-block?gclid=Cj0KCQjwlPWgBhDHARIsAH2xdNdd933LO0jk5B Vqz85qmtTjxM_4lxrUrereK1M_mJnzrenWDQjZo2caAnk-EALw_wcB
You need one of these Kevin, it will probably cure all your noise problems.
https://www.futureshop.co.uk/chord-poweraray-professional-noise-reduction-block?gclid=Cj0KCQjwlPWgBhDHARIsAH2xdNdd933LO0jk5B Vqz85qmtTjxM_4lxrUrereK1M_mJnzrenWDQjZo2caAnk-EALw_wcB
I'd bet money it wouldn't.
You need one of these Kevin, it will probably cure all your noise problems. I heard one here the other day it was totally gobsmacking but so is the price!:eek:
https://www.futureshop.co.uk/chord-poweraray-professional-noise-reduction-block?gclid=Cj0KCQjwlPWgBhDHARIsAH2xdNdd933LO0jk5B Vqz85qmtTjxM_4lxrUrereK1M_mJnzrenWDQjZo2caAnk-EALw_wcB
:lol:
For 7k, I could rewire my house, and if you change the cable on the Chord, you can add another 1.5k :rfl:
Last night, and so far this morning, there is a very faint buzz. Almost like the RFI is trying to break through, but can’t quite manage.
It would seem that the culprit is RFI on the aerials, I mean interconnects, on the turntable leads, quite possibly just the earth wire.
Apart from a ferrite, how can I make it less susceptible to RFI?
It is a really thin cable and I have wrapped it round a ferrite I bought for my mains cable.
I am thinking of replacing it with a thicker wire, where I can clip a ferrite on properly. If I do this, I could also shield the cable, or use some RG306(?) coax for the Tt ground and leave the shield floating?
Faraday cage ? Not sure how you'd implement it but it would certainly work.
Worst case, I could have a fly lead going to mains earth, but the idea of a shielded grounding cable - :mental:
I think there is a mobile phone mast about 1km away. This could be the source, but I think I need to stop have an aerial between my TT and Phono-stage.
just get rid of the bloody TT altogether, more trouble than it's worth in more ways than one.
:lol:
That would certainly fix the issue.
It is a bit extreme though.
you're a die-hard mate, I will get you a bloodstained undershirt for Christmas.
Funny enough been reading of this same situation with newly-found hum on a few forums lately. All involving turntables. 5G roll-out to blame? Maybe.
It could well be.
I have just built a TT grounding cable with a floating shield. So far, so good, but it has only been plugged in for 10 minutes.
How will a completely floating shield help? It won't act as a Faraday cage.
If you want to use a screened cable, connect the screen at the source: the TT metalwork and leave it floating at the other end.
From a quick Google.
Does a faraday cage need to be grounded? Grounding a faraday cage — that is, providing a way for the electric charge from its exterior to exit — is important in terms of safety, but it is not necessary for a Faraday cage to operate. Without grounding, electric charge will remain in the exterior of a Faraday cage.
I had this argument with Richard Dunn, but I was arguing that a Faraday cage needed to be grounded. Apparently, it does not.
well it does electrocute if it isnt:lol:
An aircraft does not electrocute you, and that is an ungrounded faraday cage.
However, sometimes the simplest solutions are the best, and I don’t know why I did not think of this yesterday.
Just disconnect the grounding cable from the phono-stage….
An aircraft does not electrocute you, and that is an ungrounded faraday cage.
difference potential i guess. cannot flow inward if there is no potential difference
There is a podcast on noise and hub in this attached link, might be worth a listen?
https://parttimeaudiophile.com/2023/03/26/how-to-reduce-noise-and-hum-in-your-system/
There is a podcast on noise and hub in this attached link, might be worth a listen?
https://parttimeaudiophile.com/2023/03/26/how-to-reduce-noise-and-hum-in-your-system/
Did you listen to it?
Did you listen to it?
Nah
Nah
It's just some bloke from Audioquest flogging their tat. Infomercial. No real knowledge to be gained regrettably,
It's just some bloke from Audioquest flogging their tat. Infomercial. No real knowledge to be gained regrettably,
To be honest I did start to listen but only got through first 5 mins. Just thought there might have been something in it for Kev?
To be honest I did start to listen but only got through first 5 mins. Just thought there might have been something in it for Kev?
No the bloke's just a salesman not a technical expert.
I think it could be an earth loop problem.
Probably related to the SL1200 power supply, linking in to the arm, feeding the phono stage, and in turn linking to the preamp.
I returned the iPurifier, and have a Gnd Defender instead. So the power amp, pre amp, phono stage, DDC and TT PSU are plugged in to my mains block (Furutech TP60e). The Gnd Defender is plugged in to my phono stage. The hum has decreased dramatically.
I have the volume turned up way beyond my normal levels, and I can hear it now and again, so is it a ground loop?
Really not sure. My next step may be a different (filtered) mains block, like the Puritan Audio jobbies, as this is driving me mad.
I may swap out my cables from the phono stage to pre for some coax based cables, in case it is the shield (connected at one end) acting as an antenna.
I'd bet money it's a ground loop. Might be wrong but I'd try the various solutions to that first.
Power conditioner or filter might remove some very high frequency noise but since you can hear the noise it's not very high frequency.
I have tried earth straps from the different equipment, and nothing seems to change it.
I have done some extreme cable dressing, which I never bothered with before, and no real change.
I still get the occasional burst of hum.
What does EMI sound like?
There is a podcast on noise and hub in this attached link, might be worth a listen?
https://parttimeaudiophile.com/2023/03/26/how-to-reduce-noise-and-hum-in-your-system/
Thanks Jim. I had a listen to a lot of it. Most things I have already tried, but thanks for thinking of me.
Thanks Jim. I had a listen to a lot of it. Most things I have already tried, but thanks for thinking of me.
No problem just thought there maybe something in there that might be worth considering?
AJSki2fly
28-03-2023, 08:00
I recently had a similar issue that I thought was an Earth-Ground loop issue, and spent several months trying to track it down. Like you I tried various leads, earth straps, mains cables etc. It turned out to not be an earth loop, and I found it by accident when I got a new Hifi stand, initially it disappeared when setting the system back up and then it came back, and I did not know, or could not think what had caused it.
Then one day I had to move the Hitachi Tuner to get to the pre-amp to change some settings. I powered the system up and you've guessed it no annoying hum in the background. The difference was the tuner was not in place or plugged in. So I put it back and plugged it in, not powered up, and immediately the hum returned. I then simply unplugged the Tuner and hum went. The Tuner is not directly earthed it has an old 8 socket, live and neutral only, the issue was if plugged in the unit was on standby with the transformer powered up, so it was radiating a nice 50Hz RF that the system was picking up somewhere, so now unless I am listening to the Tuner it remains switched off at the socket.
Your occasional burst of hum is odd, but if you have not already done this it might be worth unplugging everything apart from pre-amp and amp in the system,powered up, and then plugging one in at a time to the mains to see if the hum returns. I would even try removing the Furutech TP60e and replacing with basic simple extension blocks, you never know.
I hope it helps, I know how frustrating this sort of thing can be.
Thanks Adrian. I shall investigate further.
I have already replaced the TP60e with a big standard unit. No difference.
This morning, I have unplugged the power line network adapters, and fitted a cheap filter. The hum is still there, ever so slightly, but less pronounced at the moment. So it is not them. It does not sound like the typical noise on these devices.
Earth leads have been fitted to pre, phono and amp, so I don’t think it is an earth loop. I guess I could detach the internal earth lead in my SL1200 and see if it is that.
All 2 pin plug devices are unplugged, electrical and signal cables. I need to wait to see if the hum/buzz comes back.
Yep, it is still there….
I have now swapped out my Phono stage, only thing left to do really.
Silence…..
I have found the source.
i thought you had already removed the phono?
To be honest, I am losing track of what I have done….
With a SS phono, there is no noise. With my hybrid phono, there is now a slight noise.
AJSki2fly
28-03-2023, 10:58
To be honest, I am losing track of what I have done….
With a SS phono, there is no noise. With my hybrid phono, there is now a slight noise.
Hi, you say hybrid phono so I presume a SS/Valve design?
What valves does it have? Some are very microphonic and can easily pick up RF interference especially from transformers? I would try siting as far away from other gear as possible using some long cables, obviously you will be a bit restricted but the Phono lead from the TT. so you might need to move the rest as far away as possible to try it out.
My Sunilda phono stage(SS/Valve) will pick up mobile phono data feeds if I put it near it, again RF pick up.
Yes, self built on a blank BB3 PCB.
Siemens PCC88 x 2
New production Tesla ECC803S gold pin.
I may be kicking myself later…. And your comment above may have hit the nail on the head.
Valve damping rings installed, buzz is probably the lowest it has been for a while at the moment.
The 5G mast is 1.4km from my house.
i did read once that 5g, and possibly other emmiters can affect speaker cable too and the person started using shielded cable... dunno if its true tho.
Firebottle
28-03-2023, 16:21
RF can be picked up by the speaker cables, the problem arises when the impedance seen from the amplifier output isn't low at very high frequencies and the RF finds its way into the amplifier.
Usually cured or prevented by having a Zobel network across the speaker outputs.
Looking back on everything I have done, the only time the phono stage has been dead quiet was with the AG1500 providing the power. This would suggest to me that it is mains borne interference, which a phone pre amplifier is likely to be susceptible to, more than anything else.
The next stage for me is likely to be an investigation in “non-HiFi” power filters.
I will also isolate the phono stage a good distance from everything else and see what that gives.
The system has been on for half an hour since my latest fix.
So far, no hum.
Usually it makes the noise just after I post here, so yes, I am tempting fate, deliberately, as I ordered an Isotek Gemini earlier today, and I still have time to cancel the order.
In fact, I have just heard two very faint buzzes. It has to be power related, as I have put ferrites on the internal power cables of my phono stage.
The noise is still there, but much more acceptable now.
not silly expensive but not cheap if you don't need it. some of these things can destroy dynamics alas so if you dont need then best without but if its needed....
i used my regen when i needed it but later they fitted a new tx down rd and it cleared al the crp i was getting on mains.
It was relatively cheap compared to the rest of the system. I can send it back if it does not work….
This is the quietest my system has been for a while.
Hardly any buzz.
I may have to rethink my cabling inside the BB3. I may not have laid it out optimally to avoid perturbing the signal.
I am going to give the Isotek a go, feeding the pre and phono, and see if that works.
If it is power related, I may have to invest in a bigger/better filtering mains block.
phonos, especially mc's are super sensitive and valves can be to so mixing both can cause issues if there are issues with power emi etc around. i had an issue that turned out to be a mains cable that, although not silly close turned out to be the issue.
I am determined to fix the hum. I built the phono stage, so I want to keep it.
If the power filter does not fix the issue (I believe it will based on the impact the ferrites have had) then I will rearrange my rack, but that will be a pain as the cables are built to length.
I am sure I can make some space around the phono if I need to.
Isotek Evo Gemini is in the house.
I have it plugged in, feeding the phono and pre and for the last half hour, there has not been the faintest sign of a buzz. I hope it continues.
If not, it goes back…
That's good.
Still have to get to the bottom of my ground loop. Not there with my Philips pre but if I put any of my other pre amps in it's like an angry bee.
It’s annoying. Mine got to a point where I could live with it, but ideally wanted it gone.
There's no way I will live with any amount of hum or buzz. Just defeats the whole objective. Might as well just listen through an Alexa or some other piece of crap.
I agree, hence my stubborn attitude to fix it.
I agree, hence my stubborn attitude to fix it.
I just don't have the energy to seriously tackle it right now. There are a few things I have not tried yet that might work.
I have music with no hum with the Philips, that's good enough for the moment.
Ground loops are the worst thing ever, so hard to solve. And even when you do fix them you don't really know exactly why the fix worked.
I have been thinking about this during a quiet day at work.
There may have been a basic point I have overlooked.
The phono stage is built into an anodised aluminium case. The anodising has been removed to ensure a good contact is made for earth bonding.
However, the mating face of the case are still anodised. To get good EMI/RFI rejection, then ideally these should be metal to metal contact, so I may have to remove a spot locally on each joint to improve the shielding, or fitting a small bonding strap between parts of the case.
I shall investigate further.
Aluminium oxide is non-conductive, so removing locally it seems sensible.
if it screws into the case then the screw should theoretically be a good conductor.
Unless they are inserted into an anodised countersink, using anodised screws?
If they are self-tapping screws, then they will make an electrical contact. Even if the screws have an anodised thread, the act of screwing them in will tend to remove the anodised surface.
Is it possible for you to show a photo of the unit and the fixings?
They are not self tapping. I will add a photo, but it is a bog standard Chinese aluminium case.
Countersunk M3 (or something close) screws.
you could always re tap the hole. even same size should clean it if its got any on it... scratching inside around the hole may work a bit at least. Caustic Soda will remove it also.. also known as Sodium Hydroxide.
This is very similar, if not the actual case - https://www.audiophonics.fr/en/diy-enclosures-and-cases/diy-box-case-100-aluminium-260x311x90mm-black-pannel-p-14211.html
you could always re tap the hole. even same size should clean it if its got any on it... scratching inside around the hole may work a bit at least. Caustic Soda will remove it also.. also known as Sodium Hydroxide.
I have a set of taps in the garage. :thumbsup:
At the moment, I am not touching it, as it is quiet, but I was thinking about why it was so difficult to resolve, and what could I do to shield it better, including ideas of copper lining etc. which should not be needed if I have good electrical bonding between the component parts of the case.
This is very similar, if not the actual case - https://www.audiophonics.fr/en/diy-enclosures-and-cases/diy-box-case-100-aluminium-260x311x90mm-black-pannel-p-14211.html
looking at the photos, all surfaces appear to be anodised. Thus you will need to re-tap the holes, and re-countersink the holes on the external surfaces. It is almost certain the fixings are metric (M3), so I would replace them with un-anodised steel screws. This should solve the problem
Ideally I would remove the anodising from all mating surfaces, but the above should be sufficient.
Good luck. :)
I have just disassembled the case, and removed all anodising from the mating surfaces, and rebuilt the case.
Will it make any difference?
I have my doubts, but it can’t hurt.
I have just disassembled the case, and removed all anodising from the mating surfaces, and rebuilt the case.
Will it make any difference?
I have my doubts, but it can’t hurt.
Let us know the result Kevin. :)
All I can tell you is that the resistance between the different parts of the case is now reading 0 ohms, where there was a very slight resistance before.
I really doubt it will make a difference.
As an update, I believe that the hum problem has been fixed.
I replaced the 7805 voltage regulator with a Texas Instruments LM340T-5, as well as doing everything else listed here, and got quite a while I had had no issue.
I am happy.
But it came back…
I removed all the internal ferrites. And it was no different.
When doing this, I noticed a whiteish circle directly under one of the capacitors, so as a precautionary measure, I fitted some new Nichicon capacitors. At normal listening levels, I can not hear the hum. I really need to wind the wick up a bit.
I am sure that I have not yet found the root cause, but as long as it does not affect the enjoyment of me listening to music, I can live with it.
The hum is back.
The AG1500 is back in the system. The hum has gone.
So it is 100% mains based.
I am thinking of building and fitting one of these - https://www.atlhifi.com/shop/assembled-pcbs/emi-rfi-common-mode-filter-assembled-and-tested-pcb/
Do you think it will work?
This is the noise in question:
Long version/real time (3 minutes - 33Mb) https://drive.google.com/file/d/14awnglOdIVO4zyxnaeo4K2zBVIZwk6HA/view?usp=sharing
Condensed version (16 seconds - 3Mb) https://drive.google.com/file/d/11W048At3m5d7KcalhMxty-9un6VDKxOY/view?usp=sharing
Any ideas on what this is, or more importantly, what is causing it?
Access updated ;)
And thanks.
Not working for me - I can't hear anything. :scratch:
Short version has it at 2, 4, 8 and 12 seconds.
I'm just hearing his not hum, must be below the FR of my laptop speakers.
i heard it on my lappy. its not loud and shot burst. could be a lot of stuff i guess from dodgy cap to something coming in on mains..
It is not present when the AG1500 is connected, so it is mains based.
So, is fitting an isolation transformer before the transformer in the phono stage a crazy idea?
Use the 1500. If it's like mine it can sit on its side tucked away at back or side .my display turned to vertical mode too.
That is what I am currently doing, but I would like something more aesthetically pleasing.
I have played with Audacity this morning.
I have reduced the hiss, and performed a spectrum analysis of the sound clip.
As I thought, this is a 50Hz noise and it's harmonic. So it would seem that the only option to remove it is a mains regenerator?
Or would an isolation transformer work in this situation?
Here is the plot:
https://drive.google.com/file/d/1BussEKjYFLIOfFVnNHTQ5qxh0FekSQo1/view?usp=sharing
If it was me I'd just get another phono stage and have done with it. You're talking thousands for a proper power regenerator.
Who would want to buy a 2nd hand "noisy" phono stage?
I would need to sell it to help fund a new purchase.
In the short term, I can fit another phono stage, if I wanted to.
I have 5 MM stages and 3 MC stages "available", but they are not mine.
Have you tried a different phono stage?
I'm assuming you have and if it removed the noise and it was me I'd be putting a different one into play especially if it was bugging me.
Yes. No problems with the other phono stages. The Reflex M and Accession M both work fine, but I have to keep shipping them out when people want to borrow them. ;)
The AG1500 removes the problem on the BB3, so I have noisy mains that the BB3 is susceptible to.
Ideally I want a simple solution to get rid of that noise, that I can fit inside the case.
If I can't do that, I will keep the AG1500 in place.
I'm not convinced about the noisy mains thing, everyone's mains is noisy. If it was a real problem hi-fi wouldn't exist.
Is it not more likely it's some sort of ground loop? Using the AG1500 might be fixing that?
Now I know it is most likely to be a 100Hz interference signal, I am also thinking it is a ground loop issue.
But why is it just the analogue part of the system affected?
ground loops can be buggers especially if the set-up is complex i.e lots of boxes.
The BB3 will probably be fine in a different system.
I am going to swap my pre out, and see if it is a mixture of SE and Balanced connections.
But thinking about the last statement, the noise was present when the BB3 was the only thing connected to the mains, and the audio clip was done. It fed the PC sound card directly, so a change of Pre is not going to help.
The PC was connected to the mains though? And the phono stage was connected to the PC?
Load of ground loop threads here https://www.audiosciencereview.com/forum/index.php?search/43190210/&q=ground+loop&c[title_only]=1&o=relevance
You might find a solution there - or at least more things you can try.
I have just altered the grounding “scheme” of my BB3, and the hum has reduced significantly.
It is not 100% gone, but I am almost there.
I do have to point out that it is with the volume cranked right up at levels I do not normally use, with no music playing.
I am almost at a point now where the hum is acceptable.
Lawrence001
16-12-2023, 13:21
I do have to point out that it is with the volume cranked right up at levels I do not normally use, with no music playing.
I am almost at a point now where the hum is acceptable.
Is this more to do with the fact you know it's there rather than the impact on the music then? I'd try and live with it for now and you might forget about it.
Is this more to do with the fact you know it's there rather than the impact on the music then? I'd try and live with it for now and you might forget about it.
Totally.
I don’t believe there is much impact on the music, but I want to minimise stray signals in the phono stage.
I think I have actually nailed it.
It has taken long enough….
In the end, what caused the hum?
Lawrence001
16-12-2023, 20:52
I think I have actually nailed it.
It has taken long enough….Rather enigmatic [emoji23]
In the end, what caused the hum?
Either the fridge/freezer (Samsung “digital compressor”) or the Fridge, or the Freezer.
Ferrite beads fitted on all three and the level and occurrences of the hum has dramatically decreased.
At normal listening levels, I can no longer hear it. If I wind the wick right up, you can just about make it out.
Actually, I give up on tracking down the cause.
It is back with a vengeance….
The AG1500 is going in, and staying in for the foreseeable future.
And my AG1500 is showing me that the AC is varying wildly from 221 V to 232 V as I watch the input voltage.
You got some massive power user near you. One of my mates monitors his electrical supply voltage and it sure takes a dip when his next door neighbour switches on his electric furnace!:eek:
We have a couple in the area.
Cereal collection points, where I believe they also dry the grain.
Either that or the AG1500 is playing up.
I know you're convinced it's Mains borne, but.............
Is it a constant Hum/Buzz or intermittent. You have mentioned (and the title of the thread is ''Occasional.....'')
Could it be an Internet Router?
Cordless 'phone and Base station? They send int't signals out to one another to check they're still 'there'.
Mobile 'phone? These int'tly send/receive short bursts of info.
All the above can be picked up by Phono Stages, especially Valve ones.
Try unplugging everything for a night or two, you'll like going off-grid !!!!
Then plug things back in one by one until the culprit is found.
Just a suggestion, all worth a go.
J.
Thanks Jim.
It is a 100Hz and 200Hz noise, so for me, it is mains based.
I don’t use a fixed phone anymore, so the base stations have been unplugged a long time ago.
The internet router has been turned off, and it made no difference.
I tried all of this when the family was out, and also turned off the mobile phones.
The noise was still there.
It is intermittent, and low level. My money is it being my air source heat pump, so I need a way of filtering this noise.
I have been reading up about this, and it seems that this is due to the full inverter in my heart pump, injecting harmonics back into my mains, and it is suggested that a line reactor may fix it.
I thought lune reactors were a three phase thing? Any thoughts on this?
I assume "heart pump" is a misspelling of heat pump.
A mains conditioner will be of little help as they have to pass the mains components of up to a few hundred Hz to allow rapid transient switch-on rise times.
It would seem that your heat pump uses a variable speed motor (VSD) and use an inverter, which as you have found out will cause switching spikes at harmonics of the nominal mains frequency. I think you will need to consult a qualified electrician for advice, as anything designed for audio use will be inadequate.
Heart pump is indeed an autocorrect.
I am looking at solving the issue, rather than curing the effect, so I think you are correct. A qualified electrician will be required
I recently addded a common mode noise filter to the BB3, as I had a PCB gathering dust.
It is now silent, but the heat pump only heats the hot water now, so is not on for so many hours a day.
The original case is now pretty full, so I am going to rehouse the BB3 in a bigger case that will give me better separation between components in there.
https://www.diyaudio.com/community/threads/interesting-article-about-mains-filter-amplifying-noise.412589/
An interesting article.
https://www.diyaudio.com/community/threads/interesting-article-about-mains-filter-amplifying-noise.412589/
An interesting article.
Agreed - but nothing in it that should come as a surprise. It also 'criticises' Shaffner filters which is unfair if they are being used outside their specification.
Regarding Schaffner's CM and DM performance figures as a function of frequency, being only measured for terminating impedances of 50 Ohm, however if you delve further you can find similar measurements for a source impedance of 0 Ohm and an open circuit load. The IEC assumes the mains source impedance is 0.4 + j0.25 Ohm (IEC 725:1981).
The author hints that at high frequencies (that is above 50Hz) the mains distribution system ought to be treated as an RF transmission line. Well asuuming the dielectric insulation is PVC (Dielectric constant = 3.2) then the wavelength/2*pi at 20KHz is 33km, so assuming the distance to the nearest substation is no more than 1km, then this is 0.03 of a guide wavelenth/2*pi, so transmission line theory does not apply.
But the author is correct in that filters should not be cascaded - they will interact, and quite often with reduced overall performance.
I have an Olsen 6-way distribution strip that is fitted with a Schaffner 15A filter, which I used with my audio system without any problem.
The new case arrived today.
31416
It is bigger than the last one, as I am going for greater separation between the power and phono PCB this time around.
It is a full width case, and a little deeper than the one I used originally. This should make the build easier, and hopefully neater.
Progress:
31417
Power switch and RCA socket holes drilled out by hand.
New case layout options:
https://ibb.co/BG1tkqV
https://i.ibb.co/MfXsdMD/PXL-20240729-201828414.jpg
Or
https://ibb.co/CvXD0Kt
https://i.ibb.co/MfXsdMD/PXL-20240729-201828414.jpg
Which do you think will be best?
I have gone for a variation of the 2nd layout to keep the mains cabling relatively simple, and (hopefully) tidy.
I just need to think about the best way to extend the transformer secondary cables now.
Should be back up and running by the weekend.
Pigmy Pony
31-07-2024, 05:52
Definitely option 2. The first one looks a right old mess.
I can't see any difference between the two layouts.
.
I had problems with the images not showing.
Option 2 makes the mains cabling easier/tidier.
I am just waiting for some parts before I can finish the cabling and fire it back up.
Hopefully the common mode filter will make a difference to my problem, that and further separation from the mains should mean less interference.
Pigmy Pony
31-07-2024, 13:56
I can't see any difference between the two layouts.
.
Me neither. Just a lucky guess :D
Me neither. Just a lucky guess :D
:lol:
It looks tidy without the mains cabling.
Jobs a good'un.
https://ibb.co/y5nQrpJ
No hum has been heard, yet.
I could also swear that it sounds better than it did before, but that may just be my bad aural memory.
The hum came back shortly after my post above.
I then started to check my mains and saw that there was an issue in the quality of the mains. After months of not using my BB3, I turned it on again today, for the first time in a long time.
The difference now is that the mains cable feeding the village has been replaced/upgraded.
This caused more problems, as the local transformer could not handle the increased power delivery.
Fast forward until a couple of months ago. A new transformer was installed, and we had a date in February where the connection was going to be made.
Well, that didn’t happen. Until today. A forecast 4 hour power cut, that lasted 5 hours.
I waited a while before I powered up the BB3, and finally when I did, there is not the slightest hint of occasional hum.
So basically this thread can be summarised by “Poor power supply causes phono stage hum and there is very little that can be done about it”.
At least (I hope) I am not far from a happy ending….
Firebottle
13-03-2025, 07:44
Hooray, I like happy endings.
The hum continued, although it was not as noticeable.
I think that during my desperation to fix the issue, I ordered some generic UF4007 diodes to replace what may have been faulty parts to rule them out.
These have now been changed out for Vishay SF4007 and time will tell if the generic Amazon supplied faults were part of the problem.
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