Transformers humimg........again


Yes I'm starting a new transformer hum thread. I read through most of the others, but did not find the info I was after, sorry.
Let's start. I have a dedicated 20A line for my audio gear. Gear consists of a BPT 3.5 Signature ac isolator, Jolida JD9 II phono pre, Naim 5i-2 int. amp., two REL T-5 subs, and a Clearaudio Concept TT. Now the important part, ALL components that utilize a transformer (BPT, Naim, REL's) all have transformer hum. And yes, it is transformer hum, NOT sound from the speakers. I had a buddy, who's an electrician, over last night, and we tore everything apart from the main box to the outlet, no results. Tried many other outlets in the house, with and without the BPT unit. No difference, all transformers still humming, whether alone or not. Unfortunately, my power is fed to my house from overhead lines, but so be it. I can't change that unless I move.
Question to answer, "what can I do to stop the transformers from humming?" The hum is not overwhelming, fairly subtle actually, but nonetheless, it is something I would like to eliminate.
Can anyone offer experienced or educated replies?

Thanks :)
shawnlh
You can install a balanced power transformer outside by your electrical panel to feed the 20A dedicated line. Although not to code (JEA48 can fill you in on the details ) it will cure the problem.

For more details on balanced power look up Bryson's Tourous products and Equitech they offer sub panels with balanced power transformers.

Good listening

Peter
You can minimize the effects of transformer hum by isolating the transformer from the chassis and from the circuit boards. Remove or loosen the bolt(s) holding the transformer to the chassis and place 1/8" cork under the transformers. That should help.
Emotiva CMX-2
Pbnaudio,

The BPT 3.5 Signature ac isolator is a balanced power transformer unit. It is good for 2400Va / 20 amps FLA at 120V.
http://www.6moons.com/audioreviews/bpt2/flagship.html

>>>>>>>>>>>>>

Shawnlh,

Now the important part, ALL components that utilize a transformer (BPT, Naim, REL's) all have transformer hum. And yes, it is transformer hum, NOT sound from the speakers.
Shawnlh

First off all transformers hum to some degree, some more than others, that is normal. Now if you can hear them while seated in your listening chair that is not normal.

Tried many other outlets in the house, with and without the BPT unit. No difference, all transformers still humming, whether alone or not.
Jmho that rules out DC on the mains. Had you said with a piece of equipment plugged into the BPT the transformer of the piece was quieter but the BPT was noisy, then I could have considered DC on the mains as a possibility. An isolation transformer will not pass DC from the primary winding to the secondary winding. A piece of audio equipment plugged into the BPT output would not be affected by DC on the mains feeding the primary winding of the BPT toroid transformer.

I see you live in Canada. I believe your generating and distribution power system is the same as here in the US.

Just a few things your electrician friend should check. Have him check the mains voltage at the main service electrical panel. Make sure the voltage is the normal voltage for your area.. Have him check hot L1 to hot L2.

Then check hot L1 to neutral, and then hot L2 to neutral. The two readings should be within a couple of volts of one another.
The combined voltage of L1 to neutral + L2 to neutral should equal the L1 to L2 voltage reading.

Next thing he needs to check is the Hz. It should be 60Hz possibly 59Hz.

Next have him check the voltage at the receptacle the audio equipment plugs into unload, nothing powered up, then check the voltage again with everything powered up. The voltage should not vary more than a couple volts.

As for an overhead electrical service, there is nothing wrong with them imo.

I assume the service feeding your home is single phase 120/240V nominal.

Post back your findings
.
Thanks Pbnaudio, your reply is copied, pasted, and printed. I will have electrician buddy check these points. I will report back.

Thanks muchly :)
Shawn,

Jim (jea48) is the author of the post above, he is always very knowledgable and informative about matters as your current perdicerment ( pun intended / or not 😄)

Jim points out that you already have balanced power from you power conditioner, so one question comes to mind do all your components transformers hum if plugged in by them selves or as a whole, if as a whole one of your components may have a faulty power supply which cause the other components transformers to hum.

Best of luck

Peter
Look around (no longer made) for a PS Audio Humbuster III...I found one and it works.
My experience is with toroidal transformers only. They're the circular ones. I had the same problem - hum coming from my amplifier's transformer (toroidal Plitron). Got an AVA HumDinger, hum is gone. Cost ~$125. I don't have any affiliation, and I don't sell anything.
"My experience is with toroidal transformers only. They're the circular ones. I had the same problem - hum coming from my amplifier's transformer (toroidal Plitron). Got an AVA HumDinger, hum is gone. Cost ~$125. I don't have any affiliation, and I don't sell anything."

But you must do your leg work and make sure you really need an AVA HumDinger or they will not sell you one... I tried to purchase one from AVA but he was not willing to sell me one. Told me to do all this other electrical work instead. I appreciate that somewhat, but at the same time, it would of worked on something in my office system and did not understand being rushed off the phone with no willingness to sell me an available product they offer. My guess is they build them as needed and AVA did not want to build one at the time... SO just make sure you need one or know how to explain your needs or you may be turned away... Or just go with the PS Audio Hum Buster.
You should bring one of the culprits over to a friends house and see if it has a hum problem in another house. It might not be your house wiring causing the problem!
I had taken a couple of the pieces down to my local hifi shop. We plugged them in, no hum. And that was straight into the wall socket, no filtering of any kind. I just happen to be cursed with bad ac into my home. I will take all suggestions here, apply them, and hope for something to work.
I'll also suggest an AVA Humdinger. They have a 30 day return policy, and maybe giving AVA a call would be a good call.

If they for some reason also don't want to sell you one, shoot me a message and we can see about having you try my Humdinger out in your system.
PS Audio AC regenerator. PS Audio P-5 or P-10.
Should get it, I'd think.
There are two things that cause transformers to hum, both on the AC line.

This BTW is especially true if you have toroidal power transformers.

The first is what is often called 'DC on the line' which is usually caused by a heater of some sort operating on half power so it is only drawing power when the line goes positive. This causes one half of the AC sine wave to have slightly less voltage.

This can be blocked by a fairly simple circuit- a diode and capacitor arrangement (several members have mentioned one already on this thread), that blocks the DC and thus corrects the waveform. Toroids saturate fairly easily so only a very small amount of DC (less than 1/4 volt) can make them pretty noisy. It is possible to install the DC Blocker on the line that feeds the audio room.

The second thing that can cause transformers of all types to become noisy is the 5th harmonic on the line- in the US we use the 60Hz line frequency so this would be 300Hz. The harmonic is caused by a transformer that is being used above 1/2 of its full rated capacity. This might be a transformer on a telephone pole that you and your neighbors all use. There are two solutions- have the utility replace the transformer (good luck with that, but I've seen that happen) or get a power conditioner that can block the 5th harmonic.

In regard to the latter I don't know of a 'high end audio' conditioner that can do that (OK the regenerator types can but you have to be really careful with their use to not re-introduce the same problem), but there are commercial/industrial units made that can. Elgar used to make such some years back and they are quite effective. You can find them used on ebay (the series 3000 and 6000 are the best examples). BTW they can block DC on the line too.

I had taken a couple of the pieces down to my local hifi shop. We plugged them in, no hum. And that was straight into the wall socket, no filtering of any kind. I just happen to be cursed with bad ac into my home. I will take all suggestions here, apply them, and hope for something to work.
03-29-15: Shawnlh
Shawnlh,

Did you have the electrician check the mains voltage measurements as I asked?

To high of a mains voltage can cause transformer to hum louder than normal.

As Atmasphere said in his post odd harmonics can also cause a transformer to hum louder than normal. Where your BPT 3.5 isolation transformer unit will not pass DC on the mains from the primary winding to the secondary winding it cannot block odd harmonics from the primary to the secondary.

You need to first isolate the things in your home that may be causing the problem.

Quickest way to do so is turn off every branch circuit breaker at the electrical panel except the 20 amp dedicated circuit feeding your audio equipment.
****Caution**** If the electrical panel is a bulldog or ITE pushmatic panel where you push in to turn off the breaker and then push it again to reset do not perform this test. Pushmatic breakers are notorious for not being able to reset.

For what it's worth most odd harmonic problems are caused by electronic devices within the home. Anything with a microprocessor such as a refrigerator, microwave, dishwasher, washing machine, cloth dryer, furnace, ect. Variable freq drive on a furnace can cause big time harmonics back on the mains.

Dimmers are terrible. They can even radiate RF through the air several feet, not to mention on the wiring in the home.

Check this video out.
>https://www.youtube.com/watch?v=OCK5W9vlAE0


CFL and LED lights that screw into a regular 120V socket have an electronic transformer that put crap back on the mains. Do you have a lot of them in your home?

The list just goes on and on. But many people have these device in their homes and are not experiencing the problems you are.

Sorry for the detour, back to the test.....
Plug in just one piece of audio equipment directly into the wall receptacle outlet and check for the louder than normal hum from the power transformer of the piece of equipment. Best to pick one of the piece's of equipment you took down to the local hifi shop.

If no abnormal hum, start to turn on one breaker in the electrical panel at a time. Check the piece of audio equipment each time after a breaker has been turned back on. Continue until you find the circuit that is feeding the culprit causing the problem. Next check the loads that are connected to that circuit. Isolate the problem.

IF, with all the breakers turned off you still have the louder than normal hum go outside and look up at the utility transformer that is feeding your house. You should be able to follow the secondary side wires of the transformer and see what others houses are fed by the same transformer.

Are they just houses? Any small commercial or garage businesses? Are you fairly close to any commercial or industrial facilities?

If just houses, no businesses, do you know any of the neighbors that are fed from the same utility transformer as your house? If so see if they will let you plug the piece of audio equipment in a wall outlet in their home. Check for any abnormal Hum? No abnormal hum? If no abnormal hum your problem is somewhere after the power leaves the transformer and your house.

If you take the time to do the tests I outlined, post back your findings.

Here is some stuff I found searching the Net. You will have to copy and paste. For some reason the Agon [url] xyz [/url] thingy wouldn't work right.
.
http://www.soundonsound.com/sos/jul03/articles/mainsproblems.asp

http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/mag/410pet20.pdf

http://www.psihq.com/iread/harmonic.htm
Jim

Great information as always,

Link 1

Link2

Link3

Good Listening

Peter
I posting in this thread to save it for myself... Great info here so far. Thank you.
Did the original poster’s issue ever get solved? I’ve been fighting humming preamp transformers since I’ve moved into my current house and have posted here and other places. I’ve had 3 separate preamps and all hummed. I’ve tried a lot of things attempting to troubleshoot:

1. Only having my dedicated line breaker on with all of the others off (current preamp still hums, does not at a local electronics shop).
2. Replacing my current preamp’s power supply with another one that was cosmetically challenged but hummed less (hum has gotten worse over time, will check tightness of power supply mounts when I integrate the PS Audio Power Plant in to my system).
3. A Humbuster previously and an Emotiva CMX-2 now, neither eliminated the hum, the humbuster seemed to hurt dynamics and the CMX-2 seems to be doing better with the hum and persisting dynamics, plus the minor power filtering might be helping with my multiple dimmers RFI.
4. I’m getting a PS Audio Power Plant Premier on Friday to try out. Might try with the CMX-2 in front of the Power Plant.
5. I should have those measurements done on my panel where the mains come in also.  I need to find a good and experienced electrician that I can trust.  I had one but he retired.

The hum isn’t horrible but would sure like to get ride of it. My neighborhood’s substation is powered by very high voltage lines running to eastern WA and I suspect they are the culprit. Hopefully the Power Plant with maybe the CMX-2 in font of it fixes things...
What is your line voltage? It should not exceed 125V for more than a second. If its high that could explain the problem. The PS Audio should be able to correct that.
And what are the next steps if the following checks are not in spec?

  1. Just a few things your electrician friend should check. Have him check the mains voltage at the main service electrical panel. Make sure the voltage is the normal voltage for your area.. Have him check hot L1 to hot L2.
  2. Then check hot L1 to neutral, and then hot L2 to neutral. The two readings should be within a couple of volts of one another.
  3. The combined voltage of L1 to neutral + L2 to neutral should equal the L1 to L2 voltage reading.
  4. Next thing he needs to check is the Hz. It should be 60Hz possibly 59Hz.
  5. Next have him check the voltage at the receptacle the audio equipment plugs into unload, nothing powered up, then check the voltage again with everything powered up. The voltage should not vary more than a couple volts.

Might PM some of the people on this thread directly if I don't hear anything.  Thanks everyone...
The most likely cause of a transformer mechanically humming, besides poor lamination, is DC on the AC line. That is, the + and - portions of the waveform are not equal and opposite.

DC can be injected from certain dimmer switches and switching power supplies (or fluorescents sometimes), among other things. 

If so, a balanced transformer will minimize this issue.

If not, it's a problem with the transformer's itself.

Best,

E


A balanced transformer does not seem to sort the problem of DC on the line although it does have advantages.

There is a simple circuit consisting of a bridge rectifier and four electrolytic capacitors (bypassing the rectifiers in the bridge in reverse bias mode) that can block DC. They are effective enough and cheap enough that they are often included in equipment to help prevent the noisy transformer issue.

http://www.diyaudio.com/forums/solid-state/2080-dc-filter-16.html
Scroll down to post 159.

They can also be inserted in the AC line although this should be done by a qualified technician. The circuit is compact enough that it can be installed in an electrical junction box.
Hi Shawn,
First off, you should know that transformers in NAIM gear tend to hum.
My Superline top line phono stage powered by HiCap DR power supply hums. Not all the time. When I have and can measure residual DC on the line. Also, when any dimmers are used in the house. My original Nait5's transformer also hums. I am not sure as to what extend Naim audio specs their transformers for core saturation but this is another element that triggers it at times. They are very high tech audio grade custom transformers and sometimes that is a drawback in  real world conditions. NAIM has always been an idiosyncratic company producing product as so. Much better after the passing of Julian Vereker the founder, CEO, and past designer. 
I hope this helps. Good luck with everything.

PS: You can also contact Chris West (ex-service manager at NAIM UK) at AV Options in IL (the only factory trained and authorized service center in US).

Best,

Puiu
High core saturation  margin I meant.
atmasphere
What is your line voltage? It should not exceed 125V for more than a second. If its high that could explain the problem.
+1 for checking this.

Canada is supposed to be 120v.
In Australia we’re supposed to be 230v mine measured quite constantly around 250v, incandescent light globes would last a couple of months, yes my transformers were a little noisy with a screwdriver to the ear test, but the worst is your paying more for your power, when using unregulated appliances, fridges, aircon, heaters,lighting, poweramps, microwaves ect ect.
I complained very hard, and eventually they put the whole street on a different tap on the pole transformer down the road. Now I have correct 230- 235v no more globes blowing, and my usage is down. And I swear my system sounds better, even after I re-biased my amps, back to what they were with the 250v.

Cheers George
You can put in a large isolation transformer and create your own neutral.  It is called a "separately derived system" in the NEC handbook.  I designed a 50 KVA split phase line system, 120V-0V-120V, from 3 phase 208VAC using two 25KVA isolation transformers for a solar energy lab here in CA.  This is the basic 120V/240V mains in North America.  You will also need a suitable earth ground on the output neutral.  For your system, a 10 to 12KVA isolation transformer will do, such as a Square D or equivalent.  Do get a good one, the cheaper ones have very little headroom.

The hum in my I have found in my system deals with the transformer magnetic field driving into the chassis and creating a leakage current flowing to the earth ground wire or through the RCA shields.   I don't recommend isolating your equipment from earth but you can isolate your transformers in your equipment from the chassis using grommets.  To test this theory, remove all connecting cables and plug the unit into the mains, then turn it on, and see if you have hum.  If the unit does not hum and if it does not have a earth ground in the power cord, connect the chassis to earth and see if it starts to hum.  If it does, you have found part of your problem.   Do this for each piece of equipment that plugs into the wall.

Also, I did have one obscure hum problem once but it was the receptacle where line and neutral were swapped.  I had hum every time I plugged something into this outlet.  Given what you published, I assume this is not your problem.   You can get a outlet wire checker at your local hardware store for 10 bucks or less - it will save you from opening up each outlet to check the wiring.