[David Ellis]

I need some advice regarding power filters.

I moved to a new house and my AKSA Life Force has an audible hmmmmm.  It is relatively loud and I can hear the hmmmmm from 30' across the room - with other appliances running.  I did some reading and apparantly this is caused by some DC current on my AC power line.  The result is that the Torroids in my amp hum.  This is an annoyance, and this morning I also noticed that my CD Player (Anthem CD1) is producing an audible hmmmm through the left channel.   Bah  .

Anyhow, I would like some advice regarding power filters or perhaps just putting an E core 1:1 inductor in the power line to kill the DC voltage.  Allegedly the E core transformers don't hmmmmm - or are less problematic.  The power supply filtering AFTER the transformers in my source gear is quite good, and I am not concerned about this.  Hence, I really only need to block the DC voltage (I think).

It is worthwhile to note the my amplifier did not hmmm in my old house, and it doens't hum at a friends house.  Hence, I am fairly certain the culprit is the power from the wall socket.

It would seem reasonably for the power company to be concerned about the quality of their elecricity, but they don't care.

Any help is greatly apprecaited.

Sincerely,

[TomS]

Dave,

Here is a DC blocker design that you can just wire point to point to take care of as much as a couple diode drops of DC. 

http://sjostromaudio.com/joomla/index.php?option=com_content&task=view&id=62&Itemid=27

Pretty easy to try if you have a few parts.  Occam also talked about this in the lab quite a while back for the Felix thread.

Tom

[David Ellis]

Occam also talked about this in the lab quite a while back for the Felix thread.
 

I... was not familiar with the Felix.  I tried to find the specific discussion on DC Voltage on powerlines, but was unsuccessful .  I read a significant quantity of very intereresting material about the Felix line conditioner though .

Could you provide a link?

Thanks,

Dave

[TomS]

Some discussion here

http://www.audiocircle.com/index.php?topic=50908.msg457186#msg457186

http://www.audiocircle.com/index.php?topic=25757.msg659621#msg659621

http://www.audiocircle.com/index.php?topic=50284.msg608965#msg608965

[David Ellis]

Perfect !! 

Thanks,

Dave

[bluesky]

DIY Hifi Supply also offer a relatively cheap device for this purpose called the Blokker, a small transformer for around $30 if I recall correctly.  Could be the easiest solution if DC on your mains is your problem as this is what it claims to do.

Ian

[netaron]

Couple of things I would like to suggest, even though they may not be that common:

Check your interconnects and make sure they are shielded and grounded well and also check for the possibility of ground to signal contact.
Turn off any florescent lights that may be on the same circuit.

Haron

[David Ellis]

Check your into interconnects and make sure they are shielded and grounded well and also check for the possibility of ground to signal contact.
Turn off any florescent lights that may be on the same circuit.
 

Thanks for the thoughts.  A good reminder about the basics is always helpful.  Unfortunately, I did remove the grounding pin via a plug adaptor.  My interconnects are certainly NOT shielded, but this has never been a problem in the past. // I just checked the proxmity between the CD player interconnect and the power cord for my amp.  This also isn't the problem.

I am optimistic that one of Occams' DC blocker schematics will work, and need to figure out a case setup for this.  It's doesn't have to be pretty, so I was thinking that an oversize electrical box might work just fine.

Dave