Suffering from those transformer hum blues?

Posted by: Foot tapper on 15 May 2015

I have 2 Naim systems at home:

A mac 'n dac system in the office (mac mini, DAC-V1, NAP140, PMC wall mounted speakers)

The main system Roksan TT, CDS3/555PS, 52/SC/135s, ART Alnico speakers.

 

15 years ago, our house had the electricity sub-station virtually to itself.

The main system was on its own separate, 2.5mm2, radial circuit from the electrical distribution board.

The electrical supply was basically superb.

 

Over the last 15 years, 4,000 homes and a business park have been built, all with an infestation of switched mode power supplies, fridge freezers and other polluting electrical devices.  Worst of all, ethernet over mains, or powerline ethernet plugs, has become popular with many of our neighbours.

 

As a result, the power supply transformers in the main system all started to hum progressively more loudly as the years have gone by.

 

It reached the point where the hum was intrusive during low to medium volume listening sessions.  Much worse though has been the impact on sound quality of the system.  Female singers voices started to sound a bit relentless or "shouty" and strained.  The system became a bit tiring, harsh & relentless to listen to.

 

Naturally, I had several ideas about why this was occurring.  At first, I thought that it might be the "live" acoustic of the room - curtains had been replaced with wooden slatted blinds.  Some subtle acoustic treatment helped a bit but didn't solve the issue. The arrival of the ART speakers, with their far more revealing mid-range and tweeter drivers, compounded the situation.  Perhaps the new speakers were sounding a bit hard during the inevitable running-in period?  Finally, it has been a few years since the Naim boxes had been serviced, so perhaps this was the cause? 

 

Over the last 2 years, I have gradually worked through all of these potential root causes, addressing them in turn.  And still the system gradually worsened to the point where I have been enjoying the office system far more than either LP or CD on the main system.  If music is sounding a bit strident,  lifeless and uninvolving when played on a Naim CDS3 CD player, then something is wrong.

 

After consultation with several people, including Naim R&D, I have just installed a humungous Airlink Transformers balanced power supply.  It is effectively a very large mains transformer which decouples the external mains from the radial supply to the music system.  This is connected to the wall sockets in the living room with a new, 10mm2 radial circuit.  It's a beast.

 

N.B.: This is not something to be undertaken lightly.  And it MUST be done by a qualified electrician for reasons of safety.  Double pole isolation breakers MUST be used (Airlink fit them as standard to the balanced power supply unit).

 

The result?  Music suddenly sounds sweet as a nut again.  Just sit back, relax and enjoy natural, flowing music again.  No more shouty female singers.  No more harsh sounding instruments.  The sound is warmer and richer, flowing, more detailed, more dynamic and images better.  Transients like drums and cymbals jump out in a more lifelike, dynamic way.  Most importantly, It is enjoyable and emotionally involving again.

 

Downsides?  I suspect that it is fractionally, very fractionally slower.  It takes about a minute to adjust, then I don't notice anymore, just get on with enjoying the music and ignoring the system.

 

I have subsequently tried an ISOL-8 LC unit to see if it made any difference.  It made no improvement and slowed the music down a bit too much for me.  I suspect that it was trying to do what the Airlink unit had already done upstream, so there was no benefit in this installation.  Perhaps it would have helped if the Airlink unit had not been installed - we will never know for sure.

 

Oh, and all the transformer hum in the Naim power supplies caused by offset DC voltages?  Gone.

Ah, the wonderful sound of silence.

 

Food for thought for those of us with dirty mains.  

And that is becoming the majority of us in the UK I suspect...

 

Posted on: 15 May 2015 by musicnuttyboy
Originally Posted by Foot tapper:

I have 2 Naim systems at home:

A mac 'n dac system in the office (mac mini, DAC-V1, NAP140, PMC wall mounted speakers)

The main system Roksan TT, CDS3/555PS, 52/SC/135s, ART Alnico speakers.

 

15 years ago, our house had the electricity sub-station virtually to itself.

The main system was on its own separate, 2.5mm2, radial circuit from the electrical distribution board.

The electrical supply was basically superb.

 

Over the last 15 years, 4,000 homes and a business park have been built, all with an infestation of switched mode power supplies, fridge freezers and other polluting electrical devices.  Worst of all, ethernet over mains, or powerline ethernet plugs, has become popular with many of our neighbours.

 

As a result, the power supply transformers in the main system all started to hum progressively more loudly as the years have gone by.

 

It reached the point where the hum was intrusive during low to medium volume listening sessions.  Much worse though has been the impact on sound quality of the system.  Female singers voices started to sound a bit relentless or "shouty" and strained.  The system became a bit tiring, harsh & relentless to listen to.

 

Naturally, I had several ideas about why this was occurring.  At first, I thought that it might be the "live" acoustic of the room - curtains had been replaced with wooden slatted blinds.  Some subtle acoustic treatment helped a bit but didn't solve the issue. The arrival of the ART speakers, with their far more revealing mid-range and tweeter drivers, compounded the situation.  Perhaps the new speakers were sounding a bit hard during the inevitable running-in period?  Finally, it has been a few years since the Naim boxes had been serviced, so perhaps this was the cause? 

 

Over the last 2 years, I have gradually worked through all of these potential root causes, addressing them in turn.  And still the system gradually worsened to the point where I have been enjoying the office system far more than either LP or CD on the main system.  If music is sounding a bit strident,  lifeless and uninvolving when played on a Naim CDS3 CD player, then something is wrong.

 

After consultation with several people, including Naim R&D, I have just installed a humungous Airlink Transformers balanced power supply.  It is effectively a very large mains transformer which decouples the external mains from the radial supply to the music system.  This is connected to the wall sockets in the living room with a new, 10mm2 radial circuit.  It's a beast.

 

N.B.: This is not something to be undertaken lightly.  And it MUST be done by a qualified electrician for reasons of safety.  Double pole isolation breakers MUST be used (Airlink fit them as standard to the balanced power supply unit).

 

The result?  Music suddenly sounds sweet as a nut again.  Just sit back, relax and enjoy natural, flowing music again.  No more shouty female singers.  No more harsh sounding instruments.  The sound is warmer and richer, flowing, more detailed, more dynamic and images better.  Transients like drums and cymbals jump out in a more lifelike, dynamic way.  Most importantly, It is enjoyable and emotionally involving again.

 

Downsides?  I suspect that it is fractionally, very fractionally slower.  It takes about a minute to adjust, then I don't notice anymore, just get on with enjoying the music and ignoring the system.

 

I have subsequently tried an ISOL-8 LC unit to see if it made any difference.  It made no improvement and slowed the music down a bit too much for me.  I suspect that it was trying to do what the Airlink unit had already done upstream, so there was no benefit in this installation.  Perhaps it would have helped if the Airlink unit had not been installed - we will never know for sure.

 

Oh, and all the transformer hum in the Naim power supplies caused by offset DC voltages?  Gone.

Ah, the wonderful sound of silence.

 

Food for thought for those of us with dirty mains.  

And that is becoming the majority of us in the UK I suspect...

 

Hi Foot Tapper,

 

Congratulations on resolving what was a pretty bad situation. I'm looking at doing similar so would you mind confirming what size Airlink you went for and was it a conditioned or standard version?

 

Thanks

Posted on: 15 May 2015 by MDS

Glad you've found the answer FT.  Years ago I used to suffer from clicks and pops through the speakers and determined to install a dedicated rings-main for the hi-fi when I decorated the lounge.  It was quite a palaver, getting the floor-boards up near the distributor box, hall, and the lounge itself to lay the trunking and mains cable. For the latter I used cables from Russ Andrews which was a bit expensive but the weave of it was meant to resist RFI.  Took me a few days to get it right but I've never regretted it.  Not only have the pops and clicks disappeared completely but the sound improved.  Since I've got Naim gear, which from others' experience is prone to hum, I hardly ever noticed any on my system.

 

Sounds like you've gone even further in the pursuit of a clean supply so congratulations.  An investment that will pay dividends no matter what system you put on the end of it.

 

Mike

Posted on: 15 May 2015 by 911gt3r

Hi FT.

Great story with a successful outcome. I am glad you succombed to sticking it up on the Forum board after all. See, I kept quiet!  See you soon Peter

Posted on: 15 May 2015 by Foot tapper
Many thanks Peter!
It's quite a relief to have found the real root cause of the harshness and to have sorted it out.

Thanks for your discretion. I wanted to let it run for a while and try the Isol-8 LC as well before deciding on the best final solution. This option also allows considerably more budget for delectable turntable tweaks...

All it needs then is a Statement S1 pre-amp and we are there a just like you...
Posted on: 15 May 2015 by ken c

one of the pairs of my active 4pack 135s hum quite loudly -- but is only during the day. at night when i am most likey to have serious listening sessions, they are quiet.  i find it surprising that only the 1 pair hums whereas the other pair is quiet. i wont worry about it for now -- music sounds great at night and during the day -- when music is on, the hum doesnt come through so much...

 

congratulations FT -- you see to have a working solution for your system -- which is great!

 

enjoy

ken

Posted on: 15 May 2015 by Foot tapper
Hi MDS,
It is a BPS5120MP. This is the model that the Engineering Director of Airlink Transformers recommended, once he knew the spec of the Naim power supplies.
Posted on: 16 May 2015 by Simon-in-Suffolk

FT, interesting, it sounds like a whole new town has been built around you in the last 15 years....

I see your transformer has some RFI screening  (the extent of which could be confirmed with an oscilloscope) but the DC offsets should and you confirm have been eliminated and I suspect this was causing the most drop in quality. If you look at a transformer output that is saturating on an oscilloscope.. (Ie buzzing through DC offset ) it is not a pretty picture.. and it defies reasoning that that doesn't affect sound quality .. 

Its great you have your music back 

 

PS looked up  the isolation transformer you used.. That is a heavy duty high load device.. I guess others with more modest systems could use a significantly smaller transformer.

Posted on: 16 May 2015 by Seth
Thank you! I can't express how grateful I am for this post. I've spent nearly two years trying to get my Naim system to sound right and each upgrade has brought a temporary smile, followed by the realisation that there's still something fundamentally wrong.  Harshness, sibilance, lack of emotion, dynamic compression and sometimes, just plain downright awful! (NDX, DAC, XPS, 282, 200, HC DR, Ovator s400, full Fraim, Powerlines, HiLine - plus good accoustic panels and lots of soft furnishings!)

Everything I do leads to another compromise... but on the odd, very late night occasion, I experience that amazing thing that only Naim kit has ever managed to do for me.  I live in a modern 20-floor apartment block (brilliantly well sound-proofed, thank god!) and I'm not permitted to change my wiring.  The most striking change I made recently was putting a powerline on the DAC (there already was one on the XPS) - given that this is generally not something many people think makes a big difference, it really "brought home" that I need to do something about the power.  I'd already been considering the Airlink balanced transformers, but I was put off by safety concerns and not convinced it would solve the issues I'm having.  Sounds like your experience is extremely similar to mine and that your results are what I'm hankering for! 

Thanks for sharing.
Posted on: 16 May 2015 by Simon-in-Suffolk

I have noticed that same company have  smaller balanced isolation transformers with HF attenuation for audio applications etc with three UK mains sockets with an IEC  input socket .. So it looks like you can install as well conventionally on your mains with out needing an electrician and perhaps better suited for those that don't have a dedicated spur/radial for their hifi.

Simon

Posted on: 16 May 2015 by Seth
Thanks, Simon. I must admit, I'm a little confused as to which supply I need, but I'll email Airlink to see what they recommend.  I can't believe how excited I am about buying a transformer! ;-)
Posted on: 16 May 2015 by Huge

Seth,

 

You need have no concerns over safety of balanced supply with Naim equipment, I believe that Naim have confirmed that their components are compatible with that supply mode.  In fact it's actually somewhat safer than using single ended power supply (2 lines at +/-115V as against 1 line at +/-230V).

 

 

 

Simon,

 

The only concern I have over the 'plug-in' Airlink transformers is that they are likely to be in the listening room and, being even larger toroids than the Naim components, then, if you have an asymmetric mains supply (sometimes called a "DC offset"), they may buzz even louder!

 

However I do agree that they'll improve the sound quality from the speakers.

Posted on: 16 May 2015 by Christopher_M
Originally Posted by Foot tapper:

The result [of the new gadget]?  Music suddenly sounds sweet as a nut again.  Just sit back, relax and enjoy natural, flowing music again.  No more shouty female singers.  No more harsh sounding instruments.  The sound is warmer and richer, flowing, more detailed, more dynamic and images better.  Transients like drums and cymbals jump out in a more lifelike, dynamic way.  Most importantly, It is enjoyable and emotionally involving again.

Hi FT,

When I read your thread's title, I didn't see the question mark, and my heart sank. 'Oh no not another bloody humming transformer tale', etc.

 

So I'm really pleased that it's come good for you after all your time and effort.

 

Best,

Chris

Posted on: 16 May 2015 by Seth
Huge / Simon,

Thanks for that information, Huge.  Whilst I was originally researching the "balanced supply" option, I came upon a thread on another forum where a guy was expressing his joy from using a new balanced supply with his system. He was savaged, derided and labelled an "unholy demon born of the fires of hell" by a group who told him what he'd done was extremely dangerous, that balanced power required levels of expertise beyond his puny mental faculties and that it may actually threaten the existence of life on earth, if not the physical stability of our universe itself.  The poor guy actually stopped using his supply, he was so worried, and kept asking these "helpful, educated people" if they could help him ascertain whether he could ever consider using it again - you know, perhaps if he built some kind of electromagnetically shielded bunker on a remote island somewhere.  Obviously, you can tell I didn't take all of this too seriously, but I made a mental note to ensure I understood its implications for my Naim set-up.

The other thing I've been wondering is about earthing.  Airlink only offer 2 outlets on their units supplied by a domestic wall supply, so I was thinking of buying one unit to see how my amps or source like the change. I read other suggestions that this could cause earthing issues between the source and amps - although, as I understand it, Naim elect the source as the earth reference (hence that lovely little switch on the back of my NDX and DAC), so I'm unclear on whether I need an "all or nothing" policy or whether "toe dipping" would be a good start towards "toe tapping".  If you have any insight, I would appreciate it.

By the way, over the last couple of years, I've read a lot of what you and Simon have written on this forum.  I tend to find I agree with 90% of Simon's observations (a dislike for the Powerline on the NAP250 was very similar to my preferences on the NAP200, for example) and your thoughts, missives and contributions have been very entertaining and helpful - thank you, both.
Posted on: 16 May 2015 by Foot tapper

Hi Seth, Musicnuttyboy,

At this point, my main recommendation is: seek advice from a qualified electrical engineer.

 

This is not my core area of expertise (I'm a lapsed mechanical engineer), so seek advice and read a great deal to better understand the issues and tread carefully.

 

With a normal electrical supply, we all appreciate that:

  • the earth lead is at near enough zero Volts.
  • the neutral lead is at zero Volts
  • the live lead is at fizzy Volts (fizzy being 100, 110, 230 etc., depending on where you are in the world.)

So the live is the dangerous one of the three.

 

A balanced power supply changes this.  The earth remains at zero Volts, but:

  • the live is then at +half fizzy Volts
  • the neutral is at -half fizzy Volts

Both the live and the neutral are dangerous to the touch.

Hence the need to ensure that both the live and the neutral are instantly isolated in the event of a short-circuit, system fault etc.  This is why double pole breakers are mandatory.  Just cutting off the live is not enough.

 

 

A second consideration concerns using different mains wall sockets for different parts of your system.

For example, if your system uses a mixture of linear power supplies and switched mode power supplies, you may want to use the dedicated radial supply for the Naim components and a separate household ring main socket for the "dirty" switched mode power supplies.  DACs, NAS drives, computers and some phono stages often have SMPS.  Alternatively, you may have a full AV system with the TV/video half on one electrical supply and the music system on another.

 

Now, if you introduce a balanced power supply for all the Naim components, what happens when you connect everything up?

 

If in doubt, keep the balanced supply for 100% of the system.  Seek qualified advice before mixing & matching - I see this as an issue most frequently for AV systems and computer-based streaming systems.

 

Given the above, I refer you to the second line of this post (again!)

 

The balanced power supply (BPS) contains a large transformer.  And it will have your dirty mains feeding its input.  So you should expect it to hum....

 

Airlink offers a range of "domestic", portable BPS that you may choose to put next to your hifi system.  This is a much easier, quicker option than installing one of their hard wired ones.  However, I didn't want to replace humming Naim transformers with a humming Airlink one in the living room, so here is ours in situ:

Airlink BPS5120 Balanced Power Supply in situ

 

There is very little difference in cost between the two options, but the hard wiring option ensures that the BPS is away from the living room.  It also enabled the installation of an upgraded radial supply circuit with 10mm2 cabling.

 

The reason for going for the MP option is that it allows you to select the output voltage that you want, in 10Volt steps.  If your hifi is designed for 220V or 230V mains voltage but you supply it with 240+V, then once again you are pushing the core of the power supply transformers closer to saturation, which is not ideal.  Too low a supply voltage is bad and too high isn't good either.  What we want is "Just Right".  The MP option makes this possible.

 

Next, size of BPS.  Airlink recommended 3-5kVA for our Naim system.  A smaller system would need less.

 

 

Finally, types of mains treatment or conditioning.  There are many different types of mains distortion or pollution, so there are lots of different types of "conditioning".  I wanted to knock out the DC offset (which causes transformer hum) and something called common mode noise.

It doesn't require magical, cryogenically treated, unobtainium voodoo treatment to fix, just solid electrical engineering.  There are other types of distortion/pollution in the mains that a BPS doesn't address, so it isn't a cure all.  I decided to apply the solid electrical engineering approach and see how well it worked.  It has worked out well for us.

 

There are a multitude of other conditioning devices and mains regenerators but I'm a bit sceptical about most of them. YMMV

 

Hope this helps.

 

Best regards, FT

 

Posted on: 16 May 2015 by Seth
Foot tapper,

Helps? That's amazing - thank you very much for all of this!  I'm still in the situation where I have no option but to use a wall socket supply, but if an Airlink supply removes the hum of my XPS/HiCap/NAP (which is clearly audible and louder sometimes) and replaces it with a similar level of hum, I won't really mind as it doesn't seem to bother me (wind noise on the 17th floor is much more of an issue - hang on, maybe I should move? ;-) )

Thanks again,
Seth
Posted on: 16 May 2015 by Foot tapper

Hi Seth

Pleased to help others, to the extent that our experience is relevant.  It won't be in every case.

 

I have found the Engineering Director at Airlink Transformers to be a wonderful, pragmatic and plain speaking (in a nice way) source of straightforward advice.  However, I am sure that there are other excellent makes of BPS.

 

Equally, there are pros and cons of toroidal versus traditional frame architectures for the transformers themselves.  Both address the DC offset issue and I just didn't want to go down the path of esoteric transformer magnetic coupling theory to find the 100% optimised BPS design.  I just wanted to block the DC offset voltages with a properly engineered and safe beast.

 

I too had read the advice of so called experts on other forums, the ones who demonised the poor person who had the temerity to try a BPS for his system.  So I followed the recommendation in line 2 of my previous post.  It's a simple recommendation and worth following.

 

re the noise of the BPS, Naim were kind enough to warn us about this and both the electrician and I expected the BPS to hum like a bees nest.  In reality, it is surprisingly quiet, about the same as the 555PS was before we fitted the BPS.  The 555PS is now silent.

 

Finally, a word of thanks to Naim.  I wrote to Doug for advice on electrical safety, he contacted Naim R&D and they responded within hours.  Naim didn't have to reply, yet they did so swiftly and very constructively. Sign of a great company that cares about its customers.

 

Hope this helps, FT

Posted on: 16 May 2015 by Seth
Thanks, again, FT.... and don't worry, I know the difference between shared experience and advice. I'll seek out some definitive answers before I try this in my set-up - in fact, the email to Airlink has already been sent. Still excited though!
Posted on: 16 May 2015 by 911gt3r
Originally Posted by Foot tapper:
Many thanks Peter!
It's quite a relief to have found the real root cause of the harshness and to have sorted it out.

Thanks for your discretion. I wanted to let it run for a while and try the Isol-8 LC as well before deciding on the best final solution. This option also allows considerably more budget for delectable turntable tweaks...

All it needs then is a Statement S1 pre-amp and we are there a just like you...

Hi FT.

Would love to hear an S1 in my system too, but at this rate I'd rather retire earlier than later. So maybe not eh, ATB Peter

Posted on: 16 May 2015 by Simon-in-Suffolk

Huge, well in my experience not all large toroidal transformers saturate or buzz the same way. I have some very large (and heavy) linear regulated powersupplies for my radio equipment, and they are effectively silent and dont buzz at all even when my Naim large toroidals are singing away. The design Naim have used does seem more prone to the laminates buzzing. Therefore it doesn't follow the balanced isolation transformer should neccessarily buzz, and indeed FT seems to imply it is not particularly noticeable. Perhaps the isolator transformer design requires more offset voltage before it saturates, or the laminates are set in expoxy resin or similar?

Simon

Posted on: 16 May 2015 by Mike-B

Great report FT - this seems like a good solution for a lot of users who do have dodgy mains.

There are a number of these units on the market, many free standing types, prices range from ludicrous (yes RA) to as low as £200. 

 

However these units do not make good mains "better" so peeps need to proceed with caution ........

- I know two people - both USA & no Naim units - that have bought balanced mains units & both the same make/model free standing type & not the big in-house installs like FT.  The first one really did a good job, much like FT experienced, on his hifi & to his most important AV.  The other guy bought his on the reputation of the first & from what I understand only because he had traffo hum problems. When he hooked it up the hum did not really change & the new balanced mains unit also hummed slightly.  After further investigation it seems he does not have a DC problem - I understand he got a full refund from whoever he bought it from.  

My mains is pretty good & I have a 1000VA DC filter anyhow, so as for a balanced mains unit purchase for me - "I'm Out"

 

Posted on: 16 May 2015 by Foot tapper

Hi Simon

I'll get in touch via your Suffolkimages email address re Naim's feedback.

Posted on: 16 May 2015 by Foot tapper
Wise words Mike.  
The BPS does not improve a good mains supply and it does not tackle every possible form of mains pollution.
So it is helpful, sometimes.
 
Hence the caveats that I have included in several posts.
 
Best regards, FT
 
Originally Posted by Mike-B:

... However these units do not make good mains "better" so peeps need to proceed with caution ........

 

Posted on: 16 May 2015 by Simon-in-Suffolk
Originally Posted by Foot tapper:

Hi Simon

I'll get in touch via your Suffolkimages email address re Naim's feedback.

Thanks FT, I have sent you an email back.

cheers

Simon

Posted on: 16 May 2015 by Foot tapper

I would like to make a request of anyone who wishes to post on this thread and hope that this is okay.

 

Naim very generously allows us to post on many subjects with remarkably little editorial censorship.

 

In return, the last thing that I would wish to happen, would be to cause anything to be posted that might embarrass the company.

 

Could we therefore avoid any discussions on the safety case of balanced power supplies on the Naim forum?  The hardware involved is not made by Naim and any decisions taken to install one are not made by Naim.  Safety case discussions on Naim's forum make me feel decidedly uncomfortable and a little embarrassed.

 

If anyone does wish to discuss safety case issues, please contact me directly and we can discuss it off-line, as Simon and I are doing.

 

Having said this, I am very happy to discuss the sound quality impact of a BPS on a Naim system.

 

If I am being overly sensitive then I apologise.

 

Best regards, FT

Posted on: 16 May 2015 by Seth
Understood, FT.  I do wish there was clearer guidance on the use of such equipment, but you're right, this isn't the place to discuss it.