Sound of inductors?

[soongsc]

What's so hard about dipping a coil in a can of varnish? You solder a wire to one of the leads to act as a handle,, let it hang in the can for about 15min, then hang it up for a bit to drip the excess back into the can. From there, you can let the coil air dry or stick it in a toaster oven at around 100C for an hour. This is the way we do limited run production magnetics at work. The only difference is that we use a professional transformer varnish. Plain polyurethange varnish is still pretty good, though, and a lot easier for an amateur to score..

Wouldn't the bobin be messy? I kind of wonder how well the varnish can seep to the inside coils if the coils are pretty tight. Never seen one cut apart.

 

[dhaen]

Of course sound comes out of inductors and capacitors.
For inductors, there will be magnetic fields that turn them into mini speakers.
Capacitors will stress their dielectrics, and because of imperfect construction, the vibration will leak out.

If you have a CRT monitor or TV, have a listen to all the "activity" coming from inside. It's the same thing.

 

[Thomas]

What's so hard about dipping a coil in a can of varnish?

I will defenetly pot my inductors.

Maby this will be the next supertrendy supertweak?

 

[megajocke]

During the calibration process in justmls, I played arround with diferent components verifying the calibration.

Sudenly! What's that? Do I hear a sound from somewhere? Every time I press 'meassure' I hear the noise. I realized it came from the inductor placed on top of my old denon amp I use for these meassurements. The amp chassis somehow amplified the noise. Hmm...

I tried diferent inductors and the noisiest was the 'traditional' 1.2mm2 air-core inductors. The most quiet I could find was a copper foil inductor.

No sound from capacitors though.

What is the case of that Denon amp made of? Metal? Do the coils make noise when put on wood or something else that is non-metallic?

 

[UniQ]

What's so hard about dipping a coil in a can of varnish? You solder a wire to one of the leads to act as a handle,, let it hang in the can for about 15min, then hang it up for a bit to drip the excess back into the can. From there, you can let the coil air dry or stick it in a toaster oven at around 100C for an hour. This is the way we do limited run production magnetics at work. The only difference is that we use a professional transformer varnish. Plain polyurethange varnish is still pretty good, though, and a lot easier for an amateur to score..

Hi Wrench!

What does the "professional transformer varnish" consist of, is it 2 component or..?

Cheers Michael

 

[Thomas]

Re: Re: Sound of inductors?

What is the case of that Denon amp made of? Metal? Do the coils make noise when put on wood or something else that is non-metallic?

It's metal. 🙂 The inductor still makes some noise when I hold it in my hand. The sound from the inductor gets louder when placed on anything that will resonate the sound, such as said amp case or hard wood.

I also tried a few capacitors as well. They play too!! I tried a 5,6uF boutique priced audyn plus cap against a cheap bipolar electrolyt from monacor. The result was pretty disgusting. By far, the cheap cap was the most quiet in this test.

 

[wrenchone]

Professional transformer varnish is generally single component and solvent based, though there are also some epoxy and polyester based resins out there for nastier applications ( and people with much deeper pockets). The problem is, you'll have to find a distributor the carries the stuff and buy at least a gallon of it. A pint of plain polyurethane varnish will do a lot of coils, and it's available in your neighborhood hardware store. To put things in perspective, the most common solderable magnet wire coating is nylon and polyurethane resin. To get a varnish to totally penetrate into a coil, vacuum impregnation techniques are needed. If you want to glue the outermost (read more loosely wound ) wires in the coil together to make it shut up, the dip treatment is usually sufficient. I do this all the time at work to silence noisy transformers. Of course, if you put an air core coil next to a steel chassis plate and drive it with a power amplifier, all bets are off...