Big Torroidal - Noisy

AFAIK toroids are typically quiet. Are you sure you don't have some windings bucking?

Even unloaded?

/Hugo

Are you sure you don't have some windings bucking?

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When you say "bucking", what does that mean? Curious minds want to know.

Hi

ACR wrote

Hope someone can help here. I have a new 1KVA transformer for an amp I am building (from RS componenents). I though torroids were supposeed to be quiet - this thing buzzes along and if definelty too noisy to use - even when I lift it off the bench or put it on some foam rubber. Anyone got any expereince with these things? Do I have to spend £50 and still pot the whole thing up?

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Your problem is unfortunately a common problem when using standard transformers in audio application. It is a big chance when buying those transformers made for the industrial use (very cheap) and then try to implement it into audio amps. They nearly always buzzes, hummmmsss
and noises. There have been written a lot of articles about this issue but you could start looking at Pliton transformers an their link:
http://www.plitron.com/pages/lono.htm

Make a special attention to the article: Measuring Acoustic Noise Emitted by Power Transformers
further down at this page.

If taking account to the problem, transformers built for audio applications are never cheap.

This is why I started and tried a GB for a solid state amp transformer from Avel Lindberg (former supplier to Krell). I have specified the application to be for Audion use (noise reduction is the primary issue here).

Hope this helps a little but its another issue to get your transformer to be silent( impossible if you ask me)

Regards

ACR

I forgot to tell you that the best thing to do is to send this transformer back to RS and claim a guarantee issue.

If you are lucky you could get one that is quieter than this one, or you could make a decision to choose another type of toroids if RS approves a guarantee.

Regards

The Bryston solution. Try before returning your transformer and buying a more expensive design.

http://www.diyaudio.com/forums/attachment.php?postid=328821

I have a hybrid amp, tube voltage stage and TO3 powerfets. First i tried little 50VA toroid-transformers for the fets, they where impregnated.
Later with improving my amp i ordered two Amplimo 120VA Toroids.
But after a few weeks of class a duty, they began to hum mechanically!

I informed at the manufacturer two times, but never heard anything back!

A smaller Amplimo toroid in my tube preamplified is quiet though.

A solution for this is to get special clear self drying impregnating fluid from a transformer fabric and impregnate yourself. There exists vacuum impregnating fluids also, sort of thermohardening resin.
I worked very close to a transformer firm, so i know a little how they did and what products they used.

But i never buy an Amplimo transformer again.
In germany (at Schuro.de) i can get other makes cheaper and better, impregnated!

Only yesterday in read in the german hifi-forum that toroids were pretty succeptible to noise from the supply-net ( hope you know what I mean) and then tend to humm.
Som, either look for the problem in your supply lines, try to filter the noise just before the toroid or you can fill it will resin (it isn't filled yet, is it?) to make it stiffer, less prone to vibration.

Cheers,
Dominique

I mounted some diy ferrite in series with the mains connections. Maybe they induce noise also. The humming is not always the same. Warm toroids are noisier (looser windings due to warmth)

save your money and follow up on djk's post.
there has been past discussion on toroid noise due to DC on supply lines. if this is the case for you, try blocking the DC to the transformer via circuits like the bryston approach or others in the thread. they work.

mlloyd1

djk said:

The Bryston solution. Try before returning your transformer and buying a more expensive design.

http://www.diyaudio.com/forums/attachment.php?postid=328821

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Hi,
try the DC blocker.
Toroid transformers are particularly susceptible to DC on the mains and produce mechanical hum as a result. It is often worse when mounted inside a case.

Read up the threads in the forum on DC block & toroid. They generally follow the Bryston approach. i.e. large low voltage caps in the live line with overload/bypass diodes for start up.

One of our contributors sells a kit/PCB for this problem, Peranders I think.

Impregnation varnings!

Hey, Hallo.
Have you impregnated a cheap industrial toroid? Is there anyone who have realy done this ? What was the results ?

I have tried two times bringing the humming/buzzing toroids to a professional company using vacuum and heat impregnation. The results was very disappointing: no differences at all. Money wasted.

I figured this out that the impregnation-resin does not (even if vacuum applied) reach the inner humming/buzzing parts due to the compact winding design of the polyester foil windings. Also the core could have been a "locket version" (epoxy insulated) not letting the resin entering its inner parts.

Worth thing is to use such a transformer for a class-A amps, if you didnt know what a buzzing transformer are you will know now.

Transformers for audio applications must be built for it, that is my imression.

regards

ACR said:

Hope someone can help here. I have a new 1KVA transformer for an amp I am building (from RS componenents). I though torroids were supposeed to be quiet - this thing buzzes along and if definelty too noisy to use - even when I lift it off the bench or put it on some foam rubber. Anyone got any expereince with these things? Do I have to spend £50 and still pot the whole thing up?

Comments/experiences welcome

Thanks

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Either return it or try bathing it in Formvar varnish and drying in a heated area. Personally I'd return it, because it is hard to really soak the varnish into all the windings, and the center may be filled with black epoxy, making it hard to penetrate deeply.

The reason these buzz is the wires vibrate a little if they are not wound very tightly. All you can do is try to glue them together with the standard varnish the transformer builders us, Formvar. Potting it reduces the cooling ability of the toroid, thus reducing the power output, so while it looks nice it is counterproductive. Good luck.

I've investigated this problem a bit. Most industrial toroids use unimpregnated cores. Short of unwinding the transformer, impregnating the core, and rewinding there's nothing much you can do about mechanical ( magnetostrictive ) noise. For lowest noise not only do you need an impregnated core but you need an overrated one too. For example you use a 400VA core for a 300VA transformer. As a result of all of these problems I usually have audio transformers custom made to my own specification. The good news however is that stock Antrim toroids are very low noise, even the high VA versions. The Antrim transformers were very popular in the UK when Maplin used to sell them at very keen prices; but then Maplin switched to another, and lesser, brand of toroid which was unsuitable for audio. You could order the transformers direct from Antrim at that time, but they had a moq of 10 units. As a consequence the Antrim toroids faded from view. However Antrim will now sell their transformers in single unit quantities. Return your toroid ( I know the brand you've got but I'd better not mention the name on the forum ) to RS and buy an Antrim!!

Maplin still sell toroids? That's news to me - they seem to have discontinued everything! Any idea what brand they are selling now?

Glad you found that out. I had a bad experience with an old xfmr. I connected it with no load to the mains and heard (felt) a nasty hum that made me check to see whether there was a scary movie playing on the TV. I threw the xfmr in the bin instantly, but couldn't help myself later. I pulled it and double checked the phase and this time, it was silent.

Try the DC filter. Despite esoteric claims of salesman, any high-power toroid transformer is going to buzz when some DC is present on the mains line. Buzzing is not neccessarily a symptom of bad manufacturing, it's just the core saturating due to DC and the windings vibrating due to the forces associated with the high current peaks that happen during saturation.

For example, I have an old 1500W electric heater that uses just a diode in series to obtain the "half power" setting (it draws DC from mains thus unbalancing it). When I plug that heater at half power all my transformers, not only toroids, buzz desperately. Even in these circumstances, toroids become absolutely quiet if I feed them from a DC filter (they make some noise even when the heater is not plugged, that the filter also removes).