Transformer hum - what to do?

System is CD555, full spec LP12 turntable, NAC552, NAP300 all on Fraim, Super Lumina interconnect and speaker cables feeding Focal Diablo Utopia speakers. The 555/552/300 have just been serviced and had the DR upgrades done at Naim. A massive outlay over the years to reach a system that has given me a lot of pleasure......................but not any more. Whilst the black boxes were receiving the upgrades (and went into storage for a while) I moved house. Once I had the keys to the house I had a dedicated mains supply fitted for the system, then installed the system (well, my dealer did really) and now suffer from terrible transformer hum from all 3 power supplies. This can be so bad at times (and my listening position is fairly close to where the system is situated) that I just can't listen to it. Plus I think it's probably also the case that now I know it's there I hear it more. Once most music is playing then the hum can't be heard but when playing quieter jazz or folk pieces and of course just passing the room with the system only in standby it can be heard.

I intend to try these power supplies in different socket outlets at home and then perhaps at different locations to see if the fault lies with the equipment (doubtful, I very rarely heard any hum in my previous house) or it's a mains issue, which I suspect will end up being the cause even with the separate spur.

If anyone has any ideas on other things for me to look at then I'd be grateful. if it turns out to be the mains then what do I do? Try to live with it, even though it's really bugging me at the moment? Look at some mains conditioning? Sell the system and get something without those big toroidal transformers? I'm really quite deflated with it at the moment.

I know Naim equipment can be subject to this noise with less than a perfect mains supply but really when you think about it should £50K's worth of equipment be causing such consternation. Now that I'm suffering from it I'm rather disappointed to say the least.

Original Post

A first simple step would be to switch everything off in your own house and see if the hum goes away. Even disconnect microwaves, fridges etcetera entirely.

This would at least tell you if there is some device in your house which is causing this hum.

In my case, the fridge is quite old (1993) and when it switches on, the hum increases terribly. Since the SuperNait is in a different room, it is not really an issue for me.

The vast majority of mains 'conditioners' won't eliminate hum at all (and most will degrade the musicality of the system).

As MarkAH says, unplugging / isolating everything else in the house to identify internal culprits is the first step; after that...

If the hum is being induced by the quality of the mains electricity supply (i.e. an asymmetric waveform being supplied to your house), then it's usual that the loudness of the hum varies from time to time.  If the hum is constant and unvarying, then it's probably just a fact of that particular transformer (all transformers hum, it's just a question of how loud they hum).

If the hum is from the electricity supply there are two approaches that work.  One is to use a very large isolation transformer near the CU (preferably wired CTE); this should be installed professionally.  The other is to use a "DC blocking" filter near the equipment.

I would disconnect one of the power supplies, take it to a friends house and plug it in and see if it hums in this totally different location, environment, then you would be assured it's your current home, location that is the source of the problem and not the equipment.

It may be worth the trouble to at least ease your mind.

Hi Markah, you have a great system! I suffered from a randomly humming Hicap DR and similar on the 300PS but less frequently. It was quite annoying so I've bought an Isol-8 DC blocker (high current version) on an auction site just to see if it was going to work and it did, the humming is completely gone! The hicap was also suffering from a constant very low level hum that has disappeared. 

Hi Markah, very sorry to read of your situation.

First, as others have said, try disconnecting the likely culprits that are polluting the mains at home to isolate the villain. It maybe a fridge, hair dryer etc. If you find the villain, then replace it.

If this doesn't work, read Huge's post above, as he has had some success with transformer hum.

Finally, if all else fails, do a search on this forum for a thread called "suffering from those transformer hum blues?" It is one of my threads. I tried several options before finding one that works beautifully for us.

Hope this helps, FT

Tried switching off all the other circuits in the house first of all and also plugged the NAP300 power supply (the worst offender) in a socket in another room and in all circumstances the unit still hummed. My dealer has taken it away now to try at the shop.

At least this has eliminated any other equipment or devices within the house that could have been causing the problem. I'll wait and see what he says now once it has been tried elsewhere and take it from there.

Huge posted:

The vast majority of mains 'conditioners' won't eliminate hum at all (and most will degrade the musicality of the system).

As MarkAH says, unplugging / isolating everything else in the house to identify internal culprits is the first step; after that...

If the hum is being induced by the quality of the mains electricity supply (i.e. an asymmetric waveform being supplied to your house), then it's usual that the loudness of the hum varies from time to time.  If the hum is constant and unvarying, then it's probably just a fact of that particular transformer (all transformers hum, it's just a question of how loud they hum).

If the hum is from the electricity supply there are two approaches that work.  One is to use a very large isolation transformer near the CU (preferably wired CTE); this should be installed professionally.  The other is to use a "DC blocking" filter near the equipment.

Huge - as in my previous post no "internal culprits" were found.

The loudness of the hum does vary which leads to the conclusion that it probably is a mains issue.

"Wired CTE" - could you explain what that means please? Do the two methods of eliminating the hum that you mention have any effect on the sound quality reproduced?

Thanks, Mark

Wired CTE means the transformer's secondary is wired center tap to earth.  This results in a balanced isolation transformer, in other words the voltages on the live and neutral lines are mirror images of each other (each are 115V AC, and the difference between them is 230V AC).  To ensure no detriment to sound quality the isolation transformer needs to have a high VA rating 3000VA - 5000VA are recommended.  Note this should be installed near the CU as this transformer may well hum like a beehive!

The other alternative is a series capacitor filter, there are some commercial versions available and these vary in quality.  I built my own version of one of these.

Chrissw19 posted:

It was quite annoying so I've bought an Isol-8 DC blocker (high current version) on an auction site just to see if it was going to work and it did, the humming is completely gone! The hicap was also suffering from a constant very low level hum that has disappeared. 

+1

Isol-8 DC blocker did the magic here as well -- intermittent transformer blues but nonetheless very annoying. So definitively worth a try. I got an Isol-8 DC blocker for home demo for about one week to be sure that the hum was gone before placing an order. 

A bit late to the party... in my case 555PSs and SuperCap hum when the heating pump in the basement goes on. So in the winter I get humming PSUs and in the summer as is quiet on the Eastern front. It polutes quite badly up through the mains.

If you have more than 2 phases running into the house, you could ask your electrician to try and swap the dedidacted mains one with another. Your audio circuit might be picking up some distorted wave-forms from your neighbours, from the trafo station down the road.

Also late, but :

1st. Move, 

2nd. Forget about Naim

3rd. Take Foot Tappers Advice! 

But seriously it's those massive Transformers. in my particular case, it depends on the time of the day, Sundays are usually beautiful businesses are down, or either later in the evening, when the electrical grid is not operating at it's maximum. 

Thanks Foot Tapper, I'm taking your lead!

stuart.ashen posted:

Is it possible to rearrange the room so that you are further away from the boxes? My 300 hums but 2m away I never notice it.

Stu

Hi Stu,

Initially I was going to jump in here with a big "no", which holds true for the half of the room where the hifi is situated at the moment. It could be a possibility though to move the listening area to the other half of the room (that's basically what we use as a formal dining area, separated by a big archway). Food for thought................ and thanks for the suggestion.

Mark

Power supply/transformer hum that is audible from your listening position is nasty... 

My HiCap and 200 have a slight hum too but it's only audible within 2/3 ft. from the components. As suggested earlier in this topic, a DC terminator could work very well. I tried one and everything went completely silent instantly. I didn't keep it 'cos the hum doesn't bother me so there was no need to add an extra component in the mains supply. 

A good dedicated spur could solve things too. A good thing to have in any case btw. 

Sounds like it's just a transformer that hums anyway.  It's not uncommon with large toroidal transformers the bigger the transformer the more the hum - and that's a large torroidal!

Mine also hums a bit - so I just hum along with it.
Even though it doesn't know the words (or the tune), great music still comes out of the speakers.  

Foot tapper posted:

Hi Markah, very sorry to read of your situation.

First, as others have said, try disconnecting the likely culprits that are polluting the mains at home to isolate the villain. .......

Finally, if all else fails, do a search on this forum for a thread called "suffering from those transformer hum blues?" It is one of my threads. I tried several options before finding one that works beautifully for us.

Hope this helps, FT

Sounds logical to me, clean up the juice be fore it enters the home!

And if that device hums, who cares, it's a good distance from your listening area!

Allante93!

Markah, you have my sympathies and understanding.

I have the same issue with the electrical supply in my house and the buzzing was sadly unchanged by a dedicated spur arrangement ( though the music definitely improved).

The problem has proven completely intractable in my house. Frustrating, as I can take any of the power supplies to my neighbours house and they don't buzz 

In the end the only solution I found was to move the power supplies out of the listening room completely. I was very lucky to be able to site the brain stack such that they sat back to back with the brawn stack in another room,  separated by a wall with a couple of holes in the wall to  allow cable connections. Extreme, but effective. If this might by any chance be feasible for you I fully recommend it!

Many will say that when the music is played loud enough, the buzz is drowned out. Yes and No in my experience. I certainly was only consciously bothered by it in quiet passages, but having now got to a point where I now have zero buzz and heard the musical uplift that a silent backdrop brings, it's now clear to me that even when you don't directly hear the buzz, if it's audible at quiescence, then it's always there, adding a colouration and distortion to the sound that amounts to a permanent 'downgrade' of your system. If something can be done to minimise the buzzing then I strongly recommend doing it. 

kevin J Carden posted:

Markah, you have my sympathies and understanding.

I have the same issue with the electrical supply in my house and the buzzing was sadly unchanged by a dedicated spur arrangement ( though the music definitely improved).

 

Yes a dedicated supply does improve sound quality, but it does Jack s**t at alleviating transformer hum. Plus a dedicated supply seems to measure the worst in customers homes (and including my own) when tested with a Blue Horizon Mains Analyser. My dedicated spur read 'Max' on the dial for mains noise and two radio stations could be heard coming through the analysers speaker. Others have measured similar results on dedicated spurs.

Many here seem to poo poo mains conditioners. All I can say is try one if you can in your own system and hear for yourself what the effects are. I'm not sure if any other manufacturers apart from IsoTek make a DC cancelling product that rebalances the mains sine wave to help reduce transformer hum, but if you could try their Synchro cable it may help.

A good conditioner will lower the noise floor and increase dynamics (likewise a poor design will decrease them). It will also make any time of the day a late night listening session. If you want to spend bigger bucks a good regenerator will cancel a lot of transformer hum. These types of products have come a long way in development since they first started appearing years ago, and I simply don't accept that they ruin sound quality when used with Naim. My experience in my own system and in customers systems say other wise. This great hobby is always evolving.

Check it out and see how you go.

Cheers

Rick.

Iv'e  had two humming PSUs-- and my latest CD555PSU was only slightly the worst--it was still annoying especially during late night low ambient noise times /etc

My PurePower Regenerator 2000i completely eliminated any residual of hum from the Naim PSU and with some tests /in/out of the system

--I suffered no loss at all of Dynamics/ Sonic presentation whatsoever when the  PP was inserted in the Power line.

The unit is set for 230V operation. On my current model unit the Frequency adjustment is user determined from the front panel-- with the later updated 3000i's this function is

microprocessor  controlled automatically .

Recommended to try.

D41

My Turkish grandfather used to ask to see the owner of every restaurant where he was served a bad meal. Upon seeing the owner he would give him a big hug and when asked about the purpose of the intimate embrace he explained that it was a goodbye hug since they were never going to see him there again. Now, I am sure that if my grandfather had owned a humming megabucks Naim system he would waste no time to look for the dealer to hug..

Luckily, my modest music system is well behaving, producing hums only when Glenn Gould or Keith Jarrett are being played. 

Perhaps Naim should design a double casing for its power supplies with sound insulation material in between. That could save a lot of hugs in the long run.

Ricky Dasler posted:
Yes a dedicated supply does improve sound quality, but it does Jack s**t at alleviating transformer hum. Plus a dedicated supply seems to measure the worst in customers homes (and including my own) when tested with a Blue Horizon Mains Analyser. My dedicated spur read 'Max' on the dial for mains noise and two radio stations could be heard coming through the analysers speaker. Others have measured similar results on dedicated spurs.

 

That makes very little sense, if at any, and not at all my experience with dedicated spurs. I'm finishing one in my current house now and it's my fourth troughout the years in different houses. 

I use a mains noise analyser too. Here in the Netherlands there are usually 3 phases (live) entering the CU. Not sure about the UK though. You pick the quietest on the noise analyser to feed the spur. After that, a clean run with quality components (RCD, MCB, fuse, whatever is used), and a good shielded cable can't result in more noise than the standard in house/walls wiring that usually directly feeds a bunch of other stuff too. A well setup dedicated spur should be more quiet than the rest of the house. But never ever more noisy.

@markah I've had very good results with the DC X-Terminator from Kemp Elektroniks. It's specifically designed to eliminate transformer hum caused by DC offset on the mains. Everything went completely silent immediately. Very reasonable price too. 

 

 

KTMax posted:
Ricky Dasler posted:
Yes a dedicated supply does improve sound quality, but it does Jack s**t at alleviating transformer hum. Plus a dedicated supply seems to measure the worst in customers homes (and including my own) when tested with a Blue Horizon Mains Analyser. My dedicated spur read 'Max' on the dial for mains noise and two radio stations could be heard coming through the analysers speaker. Others have measured similar results on dedicated spurs.

 

That makes very little sense, if at any, and not at all my experience with dedicated spurs. I'm finishing one in my current house now and it's my fourth troughout the years in different houses. 

I use a mains noise analyser too. Here in the Netherlands there are usually 3 phases (live) entering the CU. Not sure about the UK though. You pick the quietest on the noise analyser to feed the spur. After that, a clean run with quality components (RCD, MCB, fuse, whatever is used), and a good shielded cable can't result in more noise than the standard in house/walls wiring that usually directly feeds a bunch of other stuff too. A well setup dedicated spur should be more quiet than the rest of the house. But never ever more noisy.

 

 

And you'e used the analyser on the dedicated spur at the hi fi socket end to measure differential and common mode noise?

Hi Marhah 

 I had the same problem when I moved to 300 it drove me crazy,

eventually after trying different locations around the house just before I thought I would sell 

everything I brought a Honda generator down and put it in the garden, so I could see if off the mains grid was the answer,

 

plugged in a long extension lead, plugged in 3 power supplies, 300ps,xps2, supercap all DR, 

Fired up the genny came inside shut the back door and switched on the system and hey presto not even the slightest hum....

all this did was prove that the equipment was fit for purpose but the incoming mains supply was very poor, probably due to living 100 meters from a dry dock which runs 24/7.

still we sent the worse culprit 300psu back to the mothership and had it rebuilt,

This did help.

best thing is a balanced supply. (Airlink) in the U.K. If you have the room the have one fitted by a qualified electrician.

it doesn't stop the hum it collects it the unit hums but you get a clean supply to you naim equipment and the don't hum , hence it all depends where your incoming supply is as to whether you can fit one in.

hope this helps ( easy to test hire  a genny and fire it up)

regards Hiary

 

 

 

Ricky Dasler posted: 
And you'e used the analyser on the dedicated spur at the hi fi socket end to measure differential and common mode noise?

The noise analyser I use detects EMI/RFI, high & low frequency and narrow & wide band interference as well as DC offset and translates that to different noises through a speaker. It plugs in any socket you want. It's from Kemp Elektroniks and specifically designed for audio/video purposes. Works a treat!

markah posted:
stuart.ashen posted:

Is it possible to rearrange the room so that you are further away from the boxes? My 300 hums but 2m away I never notice it.

Stu

Hi Stu,

Initially I was going to jump in here with a big "no", which holds true for the half of the room where the hifi is situated at the moment. It could be a possibility though to move the listening area to the other half of the room (that's basically what we use as a formal dining area, separated by a big archway). Food for thought................ and thanks for the suggestion.

Mark

Not a solution by any means, but it is worth bearing in mind that, exactly as with speakers exciting room nodes or causing cancellation, the precise position of the offending unit in the room can emphasise or reduce audibility - corner location likely to be worst - and even moving only a small distance might make a difference to the loudness at the listening position.

KTMax posted:
Ricky Dasler posted:
Yes a dedicated supply does improve sound quality, but it does Jack s**t at alleviating transformer hum. Plus a dedicated supply seems to measure the worst in customers homes (and including my own) when tested with a Blue Horizon Mains Analyser. My dedicated spur read 'Max' on the dial for mains noise and two radio stations could be heard coming through the analysers speaker. Others have measured similar results on dedicated spurs.

 

That makes very little sense, if at any, and not at all my experience with dedicated spurs. I'm finishing one in my current house now and it's my fourth troughout the years in different houses. 

I use a mains noise analyser too. Here in the Netherlands there are usually 3 phases (live) entering the CU. Not sure about the UK though. You pick the quietest on the noise analyser to feed the spur. After that, a clean run with quality components (RCD, MCB, fuse, whatever is used), and a good shielded cable can't result in more noise than the standard in house/walls wiring that usually directly feeds a bunch of other stuff too. A well setup dedicated spur should be more quiet than the rest of the house. But never ever more noisy.

@markah I've had very good results with the DC X-Terminator from Kemp Elektroniks. It's specifically designed to eliminate transformer hum caused by DC offset on the mains. Everything went completely silent immediately. Very reasonable price too. 

 

 

Actually it can make complete sense, dependant on the layout of the mains distribution wiring inside the house.

A dedicated spur gives a more direct low impedance path to the muck present on the incoming mains feed.
If you eliminate internal noise sources, other, longer, higher impedance circuits will act as DM capacitative filters and reduce mains noise.

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