noisy mains transformer I can hear it across the room

[toyota man]

I have a noisy mains transformer on my new musical fidelity m6i amp it dosnt effect the sound comming from the speakers I took it back to my dealers today

who tightened up the tansformer and told me that the noise is normal for this amp I was expecting something better from an amp costing £2k I dont think I can live with this noise any advice would most welcome I would hate to have to take it back as musicaly its so good

 

[Anonymous]

First contact the manufacturer, they should be able to tell you if its normal and maybe have some suggestions. Maybe its vibrating against the bottom of the chassis and the noise can be damped but they would have more idea on this than trying a DIY solution.

 

[noogle]

Naim will sell you amps with transformer hum for far more than £2k. AFAIK it goes with the territory with toroidal transformers.

 

[toyota man]

thanks for reply are you saying live with it or is there a fix I repair commercail laundry and catering equipment lots of electronics coputer control systems so any diy fix is not a problem I would not change transformer but if some kind of damping or macanical fix is possible I have spoken to mf who have said it could be due to mains bourne interfearance I was thinking of putting a 6mm 32a supply back to its own trip board if only I could be sure this would help I would settle for an improvement in the noise problem ( before any one worries I am a fully qualified time served sparky )

 

[toyota man]

thanks for reply are you saying live with it or is there a fix I repair commercail laundry and catering equipment lots of electronics coputer control systems so any diy fix is not a problem I would not change transformer but if some kind of damping or macanical fix is possible I have spoken to mf who have said it could be due to mains bourne interfearance I was thinking of putting a 6mm 32a supply back to its own trip board if only I could be sure this would help I would settle for an improvement in the noise problem ( before any one worries I am a fully qualified time served sparky )

 

[chebby]

Don't accept the "it's normal" argument. It's an expensive bit of kit and you spent all of that money to be happy with a great musical system and NOT be fobbed off with something that (quite rightly) annoys you or forces you to consider DIY fixes. (DIY = warranty invalidated + any chance of a refund gone.)

It's new. Take it back. It's their job to fix it.

If a state of the art company like MF (or your dealer) tells you again that 'it's normal' then get a refund. (And get another dealer!)

It's not fit for purpose if transformer hum is having a deleterious effect on your listening pleasure. (Frankly, it doesn't really qualify as 'hi-fi' if it's that bad.)

 

[oldric_naubhoff]

I'm with Chebby on this one. transformer hum is not normal. and if manufacturer/dealer tells you otherwise I'd suggest you change manufacturer/dealer.

BTW. mains borne interference, if it has any bearing on the music system it will be manifested through speakers, not the transformer. but in a well designed product, and I assume a Musical Fidelity 6i is such a product, there should be no issues with mains borne interference of any sort. power supply section should filter out any AC freq or high freq interference so output devices should not know what is going on in the outside world and they should only amplify the musical signal, not mains interference. if transformer hums it means the transformer is faulty. I'd take the amp to the dealer and see if it hums in his shop too. if it does then "the mains borne interference theory" should be proven wrong.

 

[toyota man]

thanks for your input the amp was noisy at the dealers( seven oaks) it was suggested that this was normal I have never had any problems like this before going back to the seventys trio leak armstrong etc onkyo audiolab my problem is everything else about this amp is just so good any suggestions on an similar amp would be very helpfull I dont mind putting a little bit more money in the pot thanks again for your help

 

[Yves Vanhaecht]

I have a Musical Fidelity M6i for about a year now. Very pleased with it, it sounds fan-tas-tic! The only minor problem was a noisy mains transformer: it had an internal hum that was present in different ways and levels, depending on the day and even on the time of day. I returned it to the store and after a few weeks got it back with the comment that the noise level was within specification. So I consulted a few specialists and they told me that the issue was most probably not related to my amplifier but rather to my power supply: the presence of a DC component on the AC circuit causes a transfo to hum. DC is a polution that can be produced in-house (dimmer, PC, hair dryer, espresso machine,...) but even so can already be present on the net when it enters your home. They advised to look for a net filter and as such I came in contact with PS Audio. I tested their Humbuster III and the result was amazing: all the humming was gone. This Humbuster removes the DC component and has no further impact on your amp's performance, except to make it sound even better!

If this post helps anyone to get rid of this issue, it has been well worth the effort writing it!

 

[busb]

There was a thread on PFM on DC blocking filters recently. I have to admit to neither knowing they existed nor that there's a need for them, I learn something new every day. I'd say if you can hear a mains transformer from across a room, something is amiss, no ifs, no buts. Many torroid transformers are mounted on neoprene discs to dampen their humming with a large single bolt through their centre. If missing or the bolt is too loose, they may emit noise. Very large transformers maybe mounted differently.

I'd check if the humming is always present particularly in the early hours. If it ain't, I's suspect dirty mains being the cause. If the case, try to find out if an apliance is causing the problem before thinking about expensive filters. I take it that the previous amp didn't hum so the MF's transformer would be my guess at being the cause. I'd ring around a few dealers to ask them about this issue before reminding the dealer that they are responsible for sorting out the humming.

 

[busb]

This thread may help:

http://www.diyaudio.com/forums/power-supplies/161428-variations-dc-main-filter-against-buzzing-toroid-transformers-what-right.html

 

[nopiano]

Many moons ago I had a Musical Fidelity Studio T power amp. I won it at the Heathrow show in c 1986 . It was a brute but delicate too.

It hummed like a train though, and was sensitive to mains quality. I used to have a filter coffee machine that would set it off!

A few years later, I moved house and had a dedicated spur installed. It was much better but still varied during the day. I never tried to get it fixed.

Turning to your MF, as you can see they have previous. My Krell is very quiet. I'd consider rejecting it as no way should it be audible. Maybe see if you can borrow a mains treatment device, like Isotek or PS Audio. But think about rejecting it.

 

[toyota man]

Many moons ago I had a Musical Fidelity Studio T power amp. I won it at the Heathrow show in c 1986 . It was a brute but delicate too.

It hummed like a train though, and was sensitive to mains quality. I used to have a filter coffee machine that would set it off!

A few years later, I moved house and had a dedicated spur installed. It was much better but still varied during the day. I never tried to get it fixed.

Turning to your MF, as you can see they have previous. My Krell is very quiet. I'd consider rejecting it as no way should it be audible. Maybe see if you can borrow a mains treatment device, like Isotek or PS Audio. But think about rejecting it.

I am in the near future having a new boiler put in my kitchin which will mean taking the floor up so as to install new gas pipe when this happens I am going to install a 30a 6mm supply to my system I am hopeing this will bring other benifits to my system thanks for your help :cheers:

 

[andyjm]

Your amp is rated at a maximum power consumption of 680 watts, or 2.8amps at 240v. There is no point running a 30A supply.

 

[nopiano]

I am in the near future having a new boiler put in my kitchin which will mean taking the floor up so as to install new gas pipe when this happens I am going to install a 30a 6mm supply to my system I am hopeing this will bring other benifits to my system thanks for your help :cheers:

[/quote]

you won't regret it I'm sure. Have a read of Russ Andrew's articles about mains at they are very informative, even if you don't choose his wire! I used unswitched sockets with labels saying audio only, but otherwise nothing fancy.

http://www.russandrews.com/viewindex.asp?lookup=1&region=UK&currency=GBP&article_id=pgringmain_instructions&customer_id=PAA3155032913435SWLUDTEIEITUUGPP

 

[andyjm]

I am in the near future having a new boiler put in my kitchin which will mean taking the floor up so as to install new gas pipe when this happens I am going to install a 30a 6mm supply to my system I am hopeing this will bring other benifits to my system thanks for your help :cheers:

you won't regret it I'm sure. Have a read of Russ Andrew's articles about mains at they are very informative, even if you don't choose his wire! I used unswitched sockets with labels saying audio only, but otherwise nothing fancy.

http://www.russandrews.com/viewindex.asp?lookup=1&region=UK&currency=GBP&article_id=pgringmain_instructions&customer_id=PAA3155032913435SWLUDTEIEITUUGPP

[/quote]

Nopiano, I hope you didn't follow their diagram. If anyone on this forum is qualified to review an installation for compliance with Part P of the building regs, I would be very interested in their comments. I may be wrong, but I believe the omission of an RCD on the 'HiFi' spur makes this non compliant with the 17th wiring regulations for domestic installations.

That's apart from the nonsense about directional conductors - for AC mains for goodness sake....