Transformer Hum

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zebbo
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Transformer Hum

Unread post by zebbo » Sat May 26, 2018 7:16 pm

Ok, I know this has been done to death but I have a new query.
Having six massive power supplies in my lounge, the cumulative hum from the transformers can be a bit wearing.
I run everything through a mains regenerator and a BMU but still have a fair degree of hum.
I tried running everything straight from a socket - HUMMMMMM !
BMU with no regenerator - HUMMMMMM !
Regenerator without BMU - HUMMMMMM !
BMU feeding regenerator feeding hi-fi - hummmmm = acceptable

Now why the hell would that be ?. . . and is my supply still balanced ? :-? :-? :-?
Audio Grail "Sable" Garrard 401 with constrained layer plinth / SME V / Benz Micro Gullwing SLR, Phono 3 + 2X BBPSU - MEGA!, NVA P90sa, NVA Cubix-Pro, (top & mid sections). (Oh and a Pioneer BDP LX70A when I just want some background music!)

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Dr Bunsen Honeydew
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Re: Transformer Hum

Unread post by Dr Bunsen Honeydew » Sat May 26, 2018 7:59 pm

You have lots of big transformers and noisy mains. There is one more thing you can add to try and drop it more - a DC blocker - this one seems the best value.

https://www.atlhifi.com/shop/fully-asse ... d-in-case/

The last thing in the line of things before the system should be the BMU then you know you are balanced..

Stemcor1990
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Re: Transformer Hum

Unread post by Stemcor1990 » Sun May 27, 2018 9:45 am

I had a transformer hum problem which I mentioned in the TSS thread. I asked lurcher300b for some advice and he pointed me in the direction of MCRU products. I was a bit surprised by the cost so bought one of the dc blockers as per the doc’s link. I got mine via eBay.

The blocker has reduced the hum by about 80% so I’m pleased with it. I can’t hear that it has had any effect on my system so can recommend the product. If it works on my terrible mains it should work on anybody’s.

Many thanks to lurcher and the doc for their advice and guidance on the subject.

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zebbo
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Re: Transformer Hum

Unread post by zebbo » Sun May 27, 2018 10:00 am

Excellent, thanks for that Doc & Stemcor. For what it costs I had pretty much decided to buy it anyway and give it a go. MCRU's version is £250 and looks to be pretty much the same thing so it's a no-brainer really. To be honest the hum level at the moment is acceptable but if I can get it quieter without buggering up the music then all the better. Cheers.
Audio Grail "Sable" Garrard 401 with constrained layer plinth / SME V / Benz Micro Gullwing SLR, Phono 3 + 2X BBPSU - MEGA!, NVA P90sa, NVA Cubix-Pro, (top & mid sections). (Oh and a Pioneer BDP LX70A when I just want some background music!)

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Colin Wonfor
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Re: Transformer Hum

Unread post by Colin Wonfor » Mon Jun 04, 2018 8:47 am

DC blocker are good but if the voltage is still to high the hum is normally the transformer core peaking into saturation of the possible magnetic field as with DC or clipping of the mains, so try reducing the input voltage.

Some times as with some Naim (spit, cough) transformers and cheap transformers the winding wires buzzes, the core will be 50Hz/60Hz and the winding wire if a full bridge rectifier is used causes the windings buzzing at 100Hz/120Hz.

I use a trick that works 50% of the time to stop this, first switch OFF and remove from mains, take the ring clamp off and fill the centre of the toroidal with hot glue gun muck. Then with that set and and filled to about 7/10 high drill a hole through and mount transformer still with the bottom mat and a washer at the top with a 6mm dia nut and bolt, not steel brass is best.

A tip leave the rubber mount on the bottom and use gaffer tape to hold in place and cover the hole before hot glue is used this will stop the muck from flowing out.

Feedback please.
Retired.

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Colin Wonfor
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Re: Transformer Hum

Unread post by Colin Wonfor » Mon Jun 04, 2018 8:57 am

Here is a simple DC blocker and a table to show you the best for you solution.

Image
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kellerist
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Re: Transformer Hum

Unread post by kellerist » Sun Jun 10, 2018 10:02 am

I have a BMU for a few months and never heard any hum from it until now. It came as a surprise after so many time, but fortunately, I bought a filter from the Bulgarian guy the Doc recommended. (I buy every low-cost gadget what you recommend here.) I plugged it in, and the hum disappeared immediately. Thanks!

:clap: :clap: :clap: :clap:

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zebbo
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Re: Transformer Hum

Unread post by zebbo » Sun Jun 10, 2018 10:22 am

My BMU barely hums at all and, in isolation, none of the other PSU's are particularly noisy either but when they are all running together the hum is quite obvious.
The blocker hasn't made any real difference either way. The quietest running setup is the BMU feeding the Regenerator, feeding the Hi-Fi. Christ knows why its should be quieter that way around but it is.
Audio Grail "Sable" Garrard 401 with constrained layer plinth / SME V / Benz Micro Gullwing SLR, Phono 3 + 2X BBPSU - MEGA!, NVA P90sa, NVA Cubix-Pro, (top & mid sections). (Oh and a Pioneer BDP LX70A when I just want some background music!)

Geoff.R.G
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Re: Transformer Hum

Unread post by Geoff.R.G » Sun Jun 10, 2018 10:58 am

It may be worth noting that a transformer designed for use at 60Hz may have a smaller core than one designed for 50Hz*. Such a 60Hz transformer may well saturate on 50Hz with DC present. One reason commercial aircraft use 400Hz is to reduce the mass of transformer cores.

*The difference will be small but may make a difference.

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Dr Bunsen Honeydew
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Re: Transformer Hum

Unread post by Dr Bunsen Honeydew » Sun Jun 10, 2018 10:59 am

The moral of the story, is everyone has different mains (apart from voltage) because the supply companies couldn't give shite as long as it makes washing machines etc work they don't care. The result that the motors in all this gear are getting hot, cutting their life and reliability, sometimes causing burning out and catching fire (Genfell Tower) is meaningless to them, and they (the electricity companies) refuse to discuss it or admit there is a problem. THE PROBLEM, things that USE electricity don't just take it, they all (especially motors) give something back, and that is the problem we have now with coil buzz and hum caused by the distortion put back in, 'cos that is what it is.

There have been different attempts at a solution. Naim put their big transformer in a press to try and take out any looseness in the coils, it just cut down the reliability and they had transformer burn outs. We are now concentration on different cures, but as in illness all cures have side effects, sometimes worse than the problem, like losing music content. As I say in my philosophy document, the best solution is not have the problem in the first place. Tesla are on their way to the best solution in my opinion but the cost at the moment is gross. There are Chinese alternatives appearing at Alibaba but it is hard for me at my stage of life to commit to a new battle and arguments with eeeeediots.

https://www.tesla.com/en_GB/powerwall for users

And this for the National Grid https://www.tesla.com/en_GB/utilities

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