A DC Blocker to help stop transformer HUM

[voodooless]

This is the one I got. It literally saids milliguass right on it.

Anyway, the Torus had a really strong magnetic field even at about 2 feet away. It was high enough where it did not make me feel comfortable. Mu Metal does the trick, it significantly attenuates it, and it's not like mu metal is toxic, so it can only help and it can't harm, absolutely zero brainer. There are other metal alloys like mu metal you can use.

AC Milligauss Meter UHS2

Gauss meter for precise measurement of AC magnetic fields

www.alphalabinc.com

Simple smartphone data logger app can only do up to 100 Hz, but may be fine for many cases.

 

[CleanSound]

View attachment 338663
Simple smartphone data logger app can only do up to 100 Hz, but may be fine for many cases.

Whatever works for individuals' need. But I recommend everyone to measure EMF level, not for sound quality but for unknown potential negative health effect.

 

[Speedskater]

One wonders where in a residential neighborhood all this often written about 'DC' offset comes from?
In a mixed use neighborhood, maybe. But it would come and go as machines are turned On/Off.

 

[fpitas]

One wonders where in a residential neighborhood all this often written about 'DC' offset comes from?
In a mixed use neighborhood, maybe. But it would come and go as machines are turned On/Off.

I'll start the obvious, that it results from even line harmonics. So, of necessity there must be odd loads. Switchers, maybe?

 

[DonH56]

One wonders where in a residential neighborhood all this often written about 'DC' offset comes from?
In a mixed use neighborhood, maybe. But it would come and go as machines are turned On/Off.

IME it often results from appliances in the house creating asymmetric waveforms that produce a non-zero mean that looks like a DC offset. And yah, it comes and goes with the appliance, again IME. The trick was to figure out what exactly was the culprit. I have seen the effect mostly from things with motors and compressors. Most of us do not seem to have problems; I suspect having those big motor'y things on the same circuit as the sound system is rare.

 

[Haskil]

I live in a small hamlet of a small town in the countryside... the electrical lines are buried to avoid visual pollution... and no business is nearby... no illuminated signs... and my electrical installation has been completely redone and is up to standard.

However, I have four big cats who purr in the house 24/7 so loudly that I can hear them from 3 meters away even when music is playing and there is a pianissimo... At night, we hear them more than 5 meters away...
These are the four 650 Va toroids that power four Class D monophonic amplifiers that I assembled. These transformers of Czech origin were not cheap however. I have another class AB amp whose two 600 VA transformers called "R-Core" also vibrate very painfully: but it sleeps in a cupboard.

All this is a thing of the past since I made a simple DC blocker which I mounted in the air and placed in a small plastic electrical junction box.... A diode bridge and two capacitors...
It is connected on one side to the wall socket and on the other to a standard sector strip which therefore supplies the entire high fidelity channel: satellite channel and MacMini and its remote screen included... For a ridiculously low price... I think the plastic junction box from Legrand cost more than the diode bridge and the two capacitors... the very short input and output cables come from a unused extension cord...
No more humming in the 7 or 8 years since I made this handy little filter which is connected 24 hours a day.

 

[DMD]

Good morning.
It had been a long time since I had to solve the problem of the humming toroidal transformer.
The 'latter is mounted inside a mosfet power amp built back in 1990 the noise was a bit random in the sense that sometimes it was louder and sometimes it was attenuated depending on the hours of the day, and it was audible up to the listening position, about 3 meters.
I built the circuit as shown in the schematic and I must admit that the hum was greatly attenuated by bringing the ear closer to the power amp, from the listening position you can hardly hear if there is any hum.


D1-D8=1000V /10A
C1=3,3uF/100V
C2-C5=47000uF/16V

 

[Count Arthur]

Isotek make one for the low, low price of £699.00.

 

[Geert]

Isotek make one for the low, low price of £699.00.

That's because it's "really really difficult to block DC", according to Alpha-Audio.nl who reviewed this filter

 

[egellings]

That's because it's "really really difficult to block DC", according to Alpha-Audio.nl who reviewed this filter

Wut dey put in dem tings, hey? I would use an isolation transformer if I wanted to block DC, since transformers don't pass that. The capacitor approach would be cheaper and could work as well, I s'poze.

 

[DonH56]

Wut dey put in dem tings, hey? I would use an isolation transformer if I wanted to block DC, since transformers don't pass that. The capacitor approach would be cheaper and could work as well, I s'poze.

That could lead to the isolation transformer humming... The problem is DC can quickly saturate the core, causing all sorts of nasty harmonic spray as it goes nonlinear.

 

[egellings]

That could lead to the isolation transformer humming... The problem is DC can quickly saturate the core, causing all sorts of nasty harmonic spray as it goes nonlinear.

That's true, but in my case, I don't have a problem with DC on my mains, so the transformer works well and delivers its rated amperage without showing signs of saturation, which would resemble clipping although not a s sharp, as seen by a current probe connected to an oscilloscope. I would expect a DC bias to show an asymmetrical clipping (saturating), depending on the polarity of the DC bias on the winding.

 

[DonH56]

That's true, but in my case, I don't have a problem with DC on my mains, so the transformer works well and delivers its rated amperage without showing signs of saturation, which would resemble clipping although not a s sharp, as seen by a current probe connected to an oscilloscope. I would expect a DC bias to show an asymmetrical clipping (saturating), depending on the polarity of the DC bias on the winding.

I was only commenting on your post suggesting use of an isolation transformer to eliminate the hum. That may just move the problem to the isolation transformer instead of the component in question.

Aside: Appliances inside the house can introduce distortion that produce an effective DC offset (average voltage offset) so the problem is not always on the in-coming electrical service. Either way, a DC blocker is a reasonable solution if another solution is not found. In some cases, the solution could be as simple as transferring the affected circuit to the other side of the service box, though that's usually a lucky cure.

 

[Speedskater]

In a residential situation most of the appliances and such that might cause a DC offset, have an intermittent use pattern. Even electric car chargers and solar panels. So you would notice the hum/buzz coming and going.

 

[egellings]

I was only commenting on your post suggesting use of an isolation transformer to eliminate the hum. That may just move the problem to the isolation transformer instead of the component in question.

Aside: Appliances inside the house can introduce distortion that produce an effective DC offset (average voltage offset) so the problem is not always on the in-coming electrical service. Either way, a DC blocker is a reasonable solution if another solution is not found. In some cases, the solution could be as simple as transferring the affected circuit to the other side of the service box, though that's usually a lucky cure.

Are you referring to mechanical hum in a transformer that may have loose laminations, rather than an electrically caused hum? That could be a problem, especially if such a troublesome transformer were mounted in a box that acts like a sounding board, worsening the noise. I had a transformer like that and it went out the door on the toe of my boot after attempts at quieting it failed miserably. Florescent lamp ballasts, although not transformers, are still a coil of wire on iron and can vibrate annoyingly just as well.

 

[DonH56]

Are you referring to mechanical hum in a transformer that may have loose laminations, rather than an electrically caused hum? That could be a problem, especially if such a troublesome transformer were mounted in a box that acts like a sounding board, worsening the noise. I had a transformer like that and it went out the door on the toe of my boot after attempts at quieting it failed miserably. Florescent lamp ballasts, although not transformers, are still a coil of wire on iron and can vibrate annoyingly just as well.

Either. DC reduces the transformer's "linear" range, leading to saturation, which causes electrical distortion as you said, and can also cause mechanical hum. Sometimes the hum comes later, as a transformer continually saturated heats up the core, which can cause the windings to delaminate and buzz.

Mechanically isolating the transformer, e.g. using little rubber washers (bushings) or springs on the mounting tabs, can reduce mechanical buzz. (I know you know this.) In older units, the bushings can dry out and fail, so replacing them was not an uncommon part of a repair job. At least IME.

 

[Maximus_]

so gonna make a dc blocker got more dc than there should be. living in an old rental apartment funny thing is im studying to become an electrician but when it comes to dc filters my question is from ac in on bridge rectifier and the same on output if i have 4 capacitors kan i hook them up together + to + and - to - ?
sorry if my writings crap a little drunk and my now ex cheated on me so thats nice.