Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

AC Line Filter
AC Line Filter
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 30th April 2012, 02:23 PM   #21
simon7000 is offline simon7000  United States
diyAudio Member
Join Date: Nov 2008
Location: Oakmont PA
Filters rated for say 4 amps will handle the actual 12 amps or so a linear power supply peaks at. That is because the average current stays within ratings and there is some concern about selling things that do not catching fire. The issue is that the inductors may saturate at some point during the current draw and reduce the amount of filtering.

Power supplies that use an inductor for filtering will have smoother average current draw and not stress the filter or even the power line resistance as much as a straight to the capacitor filter.

Inductor filtered power supplies are most often used in vacuum tube equipment. Vacuum tube equipment is much less affected by EMI noise sources than semiconductor equipment. (Still some effect.)

Increasing the resistance by adding inductors can be estimated by allowing .2 ohms for the AC delivered through a power cord into the filter. Use the expected peak power to determine the average peak current draw. Multiply this by 3 for a typical peak current. Then that current time the added DC resistance will give you your primary side voltage loss at peak load. If it is more than 10%, some folks may hear that. Many will claim to.
  Reply With Quote
Old 30th April 2012, 05:16 PM   #22
Speedskater is offline Speedskater  United States
diyAudio Member
Speedskater's Avatar
Join Date: Sep 2002
Location: Lakewood, Ohio
Jim Brown has some excellent papers on power line filters.

Audio Systems Group, Inc. Publications
  Reply With Quote
Old 30th April 2012, 08:13 PM   #23
Ducs is offline Ducs  Canada
diyAudio Member
Join Date: Apr 2012
Wow...I didn't expect a multi page debate.

To add more fuel to the fire, here is an attenuation loss graph of Schurter DD12, 4A version

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.

. . . . . 0.1/100Ω differential mode
........... 100/0.1Ω differential mode
- - - - differential mode
_____ common mode


An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.

L 2 x 1.5 mH
Cx 100nF
Cy 2.2 nF
R 1M
  Reply With Quote
Old 30th April 2012, 08:56 PM   #24
boywonder is offline boywonder  United States
diyAudio Member
boywonder's Avatar
Join Date: Jan 2008
Location: So.Cal.
Originally Posted by Ducs View Post
Great...I am planning to use a Schurter power entry module with a switch, fuses and a filter - all in one package makes everything simpler and cleaner
Exactly what I've been using, these were pulled from prototype breast biopsy devices, now recycled into my tube amps.
Attached Images
File Type: jpg power entry.JPG (167.2 KB, 481 views)
  Reply With Quote
Old 29th November 2017, 02:24 PM   #25
donaldtong is offline donaldtong  Hong Kong
diyAudio Member
Join Date: Jun 2006
Originally Posted by mississippi View Post
My opinion:
If you hear a difference between filtered and unfiltered comes because you know when the filter was there or not.
After rectifying there is a DC voltage on your caps, and there is no difference there with or without filter.
Since you amplifiers works on DC voltages, I think the sound difference is between your ears !

Yes AC line filter does help, at least for the setup of my home equipment.
This is the REAL EXPERIENCE I got just from yesterday and I want to share
my experiences with all people who enjoy high quality music.

I've a AK4396 Dac with Singled ended FET line buffer driving my AKG K501
for listening music from my home PC. It works fantastically and the sound
quality is crystal clear, sound stage are miracle, imo.

Yesterday , I rearrange the placement of my equipment to make it more tidy.

After the tidy up work,I found the sound output from my headphone become dull. The sound is still good, but the stereo image is lost. It's still two channel, you can hear sounds come out from left and right side differently but the feeling of stereo image is lost, just like hearing a cheap earphone connect to low quality computer audio output.

I at first think that's because of my own body condition (may be two tired),
but after one day, I am sure that there is something wrong with my equipment. I then check in detail what has been changed and find out that
the DAC/headphone amp is now connected to a different A/C power band.

I then examined what is the difference between the original and new power
band. The difference is that the original power band has a A/C power line filter
(just a very cheap , some 3 dollar i think) I added 3 year ago.

I remembered that I added this filter just for fun and never expect there will have any difference. After I re-plug my DAC to the original power band,
everything goes to normal. The stereo image come back.

I am not sure it is the cause of A/C line filter that make the difference.
But for sure, the condition of A/C power source does has great influence on the sound quality. So my recommendation is that everybody should try adding
A/C line filter if it is not included in your equipment, especially if it shares
the same power source with your computer.
  Reply With Quote
Old 6th December 2017, 10:36 AM   #26
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
the pics in post1 and post24 show filters designed to be fitted through a hole in the enclosure.
Both have a recess in the plastic moulding to allow a neat hole for back of panel fitting.
Most Builders will mount these filters on the back of panel since clearly that plastic moulding is designed for that purpose.
separating the filter metal case from the hole through which it should pass allows interference to pass through that hole.
And worse the interference filter takes the cable interference to the enclosing metal can with no where for that interference to go, except via the PE connection via a long wire.

For best RF attenuation the metal can should be in contact with the enclosure hole all around the perimeter. No gaps equals no leaks of GHz interference through the hole.
This requires the filter to be inserted through the hole from the outside and then bolted in position with electrical contact from can to chassis to conduct interference direct to enclosure without having to pass along the inductive impedance of the long PE wire.

We are not done yet.
The can to enclosure connection requires good electrical contact to be effective in taking interference to the enclosure.
That requires the electrical contact to be maintained over years of operation. The contact needs a non corroding electrical gasket of protection using some air excluding jointing grease/vaseline/or All Aluminium, or All Steel connections clamped airtight.
Is the can steel or aluminium?

If the can to enclosure contact were to corrode all around, then we are left with capacitive conduction of interference. All is not lost. The frequencies are often so high that quite small capacitances will still allow the filters to work. The area around the hole and corrosion filled gap give more than a few pF, possibly hundreds of pF.
regards Andrew T.

Last edited by AndrewT; 6th December 2017 at 10:45 AM.
  Reply With Quote
Old 6th December 2017, 10:49 AM   #27
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
The filters shown in pics 6 & 7 requires the cans to be bolted to the enclosure and preferably near where the cable enters the enclosure.
The cable between the enclosure entry hole and the can terminals requires to be screened and both ends of the screen need to be connected by low impedance methods to the enclosure. This means very short pigtails, or much better: a metal clamp to pull the exposed screen into contact with the enclosure wall.
regards Andrew T.
  Reply With Quote
Old 6th December 2017, 01:32 PM   #28
Max Headroom is offline Max Headroom  Australia
diyAudio Member
Max Headroom's Avatar
Join Date: Jan 2013
Location: West Australia, near to the beach, natural ambient sounds mostly.
My experience of IEC panel insert modules and other mains filter modules correctly fitted/wired is that they do indeed reduce mains borne noise (as advertised) and a bunch of consequent downstream maskings caused by effects on circuitry of this longitudinal noise, BUT they can also cause a dullness/information loss, a low level constant distortion and a 'hardness' that I attribute to the inclusion of ferrite.
IIRC member Dvv recognises this and recommends powdered iron inductors as preferable.

According to a Youtube video showing the internals of a panel insert integrated IEC socket/fuse/filter assy, the filter input stage A-N cap (post fuse) is designed to fail short, and the A-E and N-E caps are designed to fail open.

What is the construction and chemistry of these X rated and Y rated caps ?.


Last edited by Max Headroom; 6th December 2017 at 01:40 PM.
  Reply With Quote
Old 6th December 2017, 01:52 PM   #29
DF96 is online now DF96  England
diyAudio Member
Join Date: May 2007
An X cap is not designed to fail short. It is designed to fail open, but this is less guaranteed than for a Y cap. The idea is that an X cap won't burn your house down, but a Y cap won't electrocute you.

There are several technologies used for X and Y caps. Most use plastic film, but some are ceramic.
  Reply With Quote
Old 7th December 2017, 01:57 PM   #30
tulldavw is offline tulldavw
diyAudio Member
Join Date: May 2013
I did have one fitted but took it out and the sound stage did improve by a good bit, but this was on my rig up
  Reply With Quote


AC Line FilterHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
jon risch AC Power Line Filter - q's sunrise Power Supplies 26 30th April 2017 09:42 PM
AC Line Filter-Parts Recommendations croy00 Parts 11 13th September 2011 08:01 AM
possible to filter dips in AC line? ryuji Tubes / Valves 28 7th April 2011 04:23 AM
Pics of My AC Line filter project JOE DIRTŪ Everything Else 30 20th June 2003 01:33 PM

New To Site? Need Help?

All times are GMT. The time now is 11:41 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio