DC filter


-After 4 coats. I like being overkill.


-Installed and tested!

The Mechanical Hum went down 90%. Execelent. I only hear it when my face is poiting the transformer! So for 3meters range , i will ear no more transformer hum....

I wonder if it is not soak in varnsih since was produced!

All thanks to this forum :shhh:
Now i can make the same for the other active speaker!
 
Allright after coating with wood varnish the transformer that was the source of the hum... i still got it, but less audible, thank me!
I already puted the caps and bridge on a plastic box.
My question goes for what i can do to a multimeter to check if this is doing anything...
because by hear i do not hear nothing diferent from or with a straight cable....

Put the plug (with the box) on the wall and measure it's AC (247v) that's what i go at home, with that or a straight cable.... nothing wrong there.

But to check if i got DC on it i put the multimeter in the end of the cable (plug) and measure ... but the results are weird... Multimeter is in DC 20 and shows me... the following...

0.1 to 0.2 to 0.3 to 0.4 till 0.60+ and then drops negativally on the same till -0.60+...keepin it the same all the time.

I have to measure this with a normal cable (straight)...

i am doing wrong the dc voltage measure?

 
Since i opened and removed the active board i see it was easy i decide to make everthing i can to make it quieter....

I am thinking of making a shield (metal) near the tranformer to separate the audio board...

What can i expect with that? Benefits? Cons? ... any help should be apreciated!
 
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You measure the DC across bridge rectifier when the unit is passing current to the load. Ideally it should be zero. If there is DC present then the unit is doing its job and preventing it reaching the load.

Shielding is difficult and expensive. Space and fresh air is cheaper. Unless you use such materials as mu-metal the result can be disappointing.
 
You measure the DC across bridge rectifier when the unit is passing current to the load. Ideally it should be zero. If there is DC present then the unit is doing its job and preventing it reaching the load.

Shielding is difficult and expensive. Space and fresh air is cheaper. Unless you use such materials as mu-metal the result can be disappointing.

Ok, and that translate to english is what?
You say i should measure when the active speaker is playing music, ok! I did not measure tha yet. And on what points of the bridge i measure the DC?
There is a + and a - and two ~ .
I point the red and black tip of the multimeter on what of those position with the DC on the multimeter!

Space and fresh air? What do you main by that?

I know what mu-metal is... i was thinking on something like this:
magnetic shielding foil | eBay
Ultraperm 80 Metal Shield Mumetal MU Metal Sheet Audio | eBay

or this:
Ringkern Abschirmblech Magnetic Shield Tin for Toroidal Transformer | eBay

Even a mix of them all....

What can i expect with those around the transformer? Do i need to be carefull for those do not touch the transformer in metal? Being conductive i guess....

Thanks
 
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Ok, and that translate to english is what?
You say i should measure when the active speaker is playing music, ok! I did not measure tha yet. And on what points of the bridge i measure the DC?
There is a + and a - and two ~ .
I point the red and black tip of the multimeter on what of those position with the DC on the multimeter!

Your bridge should have the - and + linked across and the caps across the two AC terminals. So you measure across the two AC tabs. Polarity of the meter doesn't matter.

Space and fresh air? What do you main by that?

I mean that shielding using metal isn't normally needed or cost effective. Putting a bit of space between the transformer and keeping it away from the sensitive parts of the circuit works better every time.
 

-So you are saying i put the multimeter where the red arrow's are pointing? And in DC, ok thanks.
What shoud i expect, reading... what is a bad sign, and a good sign?
Thanks!


And since i made the varnish trick and liked the results... i will spend money on some stuff that say's quiet even more transformers.... :)

Fisically i can't move it more away then it is... Maybe outside the speaker, but i am not that hardcore :)

What i was thinking is doing this...

-On the red circle using a hose plastic pipe from sweage and cover it with mu-metal foil sticker.

Or using this: and even foil it with mu-metal sticker sheet!
Ringkern Abschirmblech Magnetic Shield Tin for Toroidal Transformer | eBay

Is this a good idea from reducing even more the hum and all that crap involved?
 
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'Looks like you are building a nice, flammable mess. It may damp any rattling cables but if there is a failure like an open fuse, short, semiconductor or resistor burnout, you'd better check the home and family insurance policies, unless you can all look after yourselves.

Use self-extinguishing, mains electrical rated materials there or tie the cables down instead.
FWIW, in this situation, which is evidently a loose transformer assembly, it's hard to see that magnetic shielding will have much worthwhile effect, if any. Don't waste money on this as the effects you describe are a lot more mechanical, don't you think?
 
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Are you talking about the cable with DC gizmo or the varnish on the transformer?

If talking about the DC "trick" this is only for testing right now... but were you go... how she is right now...


-On a plastic box, open for now for testing more! SAFE now? Or the DC gizmo is a unsafe solution? If that's it i will use the stock cable right now.... please tell me, what you think...

As for the other transformer of the other active speaker, the transformer is already soaked in varnish! :)


And about this:

-This pic is just the board and transformer how it came from SANSOM, no mods whatsoever yet!

-Around the circle fab a box out of plastic or wood and wrap it with aluminimum foil or mu-metal foil? Any good for helping the magnetic hum of the transformer out for the board?

And on the arrows is where i measure the DC with a multimeter with the point leads (red/black)

-Is that it? When the speaker is playing hard (load)??
'Looks like you are building a nice, flammable mess. It may damp any rattling cables but if there is a failure like an open fuse, short, semiconductor or resistor burnout, you'd better check the home and family insurance policies, unless you can all look after yourselves.

Use self-extinguishing, mains electrical rated materials there or tie the cables down instead.
 
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The last pic showed foamed poyurethane sheet. This is the main problem - don't use it!
Think what happens as the amplifier heats the box as it plays. At around 55C, the MDF box material starts to slowly degrade too and plastics like foam, soon degrade and melt to mush over the PCB. I can't imagine that you are unaware of this so it should not be surprising - just don't mess with crappy packing materials and power. Cable ties should also work if you utilise box sides for support too.
 
The last pic showed foamed poyurethane sheet. This is the main problem - don't use it!
Think what happens as the amplifier heats the box as it plays. At around 55C, the MDF box material starts to slowly degrade too and plastics like foam, soon degrade and melt to mush over the PCB. I can't imagine that you are unaware of this so it should not be surprising - just don't mess with crappy packing materials and power. Cable ties should also work if you utilise box sides for support too.


-The foam wrapped on the cables? It was not me... this came stock from Samson... i never saw that until removed the board inside the speaker! And it came with a cable tie on some place for secure the cables and it have one wire for securing it to!
This all from the manufacter....

but you are saying that the foam is a bad idea? Should i remove it and use electric tape instead in the place of the stock foam?
 
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Ideally you should measure no DC across the bridge. If you do, and if its below around 1.3 volts dc then the device is stopping that DC passing to the transformer. If its 1.3v or slightly more then it means there is more DC present than the filter can stop (unlikely).
 
Ideally you should measure no DC across the bridge. If you do, and if its below around 1.3 volts dc then the device is stopping that DC passing to the transformer. If its 1.3v or slightly more then it means there is more DC present than the filter can stop (unlikely).

Allright, tonight i will do that! Thanks!
And about the box i puted that caps/bridge, allright? Safe?
 
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....The foam wrapped on the cables? It was not me... this came stock from Sme with a cable tie on some place for secure the cables and it have one wire for securing it to! This all from the manufacter....
but you are saying that the foam is a bad idea? Should i remove it and use electric tape instead in the place of the stock foam?
Perhaps I am mistaken with the type of foam plastic, such that is an approved type after all, though I doubt it. If it readily melts with a naked flame, remove it, However, I have already suggested cable ties - not tape.
I sense that you have no idea of the potential for disaster with power electronics in a closed wooden box. I suggest you look at some examples in the pictures thread (Sticky at the top of this Forum Thread List) and also in loudspeaker (multiway) forum to get an idea of how much care ought to be taken with the choice of materials and assemblies.