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ccereda 1st December 2006 12:56 PM

mains filter

I hope I am in the right forum.

I want to build a mains filter, I read the article of Decibel Dungeon:

But I do not dare since I can not fully understand the diagram and I am a little afraid given my short experience and the power involved.

Does anybody could make some idiot proof , thatís me :-( , instructions?

Maybe we could ignore the screen since I do not think it is very important for the mains cleaning.

Of course I could go for another project as long it is efficient and sure, I also would accept a kit if anybody knows one good quality and reasonable price.

Thank you


jackinnj 1st December 2006 03:13 PM

It's a good thing to be cautious where the mains are concerned. Below is a schematic for a commercially available power line filter. some of the important things to take into consideration:

1) The capacitors have to be a.c. rated for your line voltage -- they are expensive -- polypropylene types are the preferred variety.

2) The filter should be contained in a metal box, preferably sealed. If you don't put it in a metal box, it's like going to the gym, working out and getting all sweaty, then putting on clean "trow" without showering.

3) Most of the parts can be scrounged from ATX power supplies !!!

I use Corcom filters -- easier than assembling the parts -- they work quite well (very well indeed). In fact, the price of a corcom filter is about what you would expect to pay if you had to assemble the parts from scratch.

AndrewT 2nd December 2006 12:54 PM

the schematic in decibel looks complicated.
The difficult bit in the bottom half is just the indicator.
The top half is the suppressor.

Try building the top half only.
or do the very simple one that Jack posted.

You can add VDR or MOV in parallel to the first cap for extra spike attenuation.

BUT, CHOOSE your components CAREFULLY.

They MUST be rated for the correct voltage and duty.
Don't get your X caps and Y caps mixed up. It could be potentially LETHAL.

C3 MUST be Y rated caps
C1 & C2 are X rated caps.
Both types are self healing and tested to something like 2500V!

HIPCHECK 2nd December 2006 01:02 PM

to anybody reading this post, or thinking about doing any mains filtering.

** please feel free to take some nice Yrated caps off my hands**

see my previous post in trading post.

AndrewT 2nd December 2006 01:06 PM

Thanks for the offer Hipcheck.
But, Scotland is a bit far away.

dantwomey 2nd December 2006 02:04 PM

Here's a design that's been around for awhile and I put it in my CD player and it seemed to make an improvement.

Jon Risch's AC Filter

Dan :D

jackinnj 2nd December 2006 03:26 PM


Originally posted by AndrewT
Thanks for the offer Hipcheck.
But, Scotland is a bit far away.

Scotland was here 2 weeks ago (wasn't St. Andrew's feast day this pst week?). Had a lovely time at the New York State St. Andrew's Dinner -- still can't get over the haggis with single-malt. The land of cakes --

AndrewT 2nd December 2006 03:54 PM

Hi Jack,
maybe it felt like Scotland had moved to NY but, honest, some of us stayed at home to eat the oatcakes.

It was two day's ago, Thursday 30th Nov.

Our skool kids prepared a luncheon, dressed the tables, cooked a three course lunch, served it up and washed up afterwards for a group of invited guests, BRILLIANT.
The proceeds were split between the kids and a local charity.
Young Enterprise Scotland have a lot to answer for!

mavallarino 26th January 2012 01:29 PM

1 Attachment(s)
Hello all,

I'm currently designing a balanced mains filter and have a couple of questions/curiosities:

1. For safty I have a RCBO, where is the best place, before the primaries or after the secondary and/or before or after the filter network?

2. I will hooking up both digital and analogue sources and a few different types of amplifiers. Should these be filtered differently, if so, how?

Thanks in advance!

wwenze 26th January 2012 02:05 PM

You'll need one on the secondary side; as it is now any short between L/N and ground will cause current to flow between that conductor and ground through a completed loop on the secondary side, while the L and N on the primary side will still carry the same amount of current (and not trip any RCD).

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