General HIFI > Room Treatments & Tweaks

DC blocking on mains supply

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Jehuty:
Stole this thread from SNA...I think it's a good tweak and (hopefully) not that expensive:


--- Quote ---warning - do not attempt this without a very competent knowledge of what is involved and the safety required.

I have been interested in the blocking of dc voltage coming in on the ac mains line for some time and after a discussion with a client who is the head of foxtel engineering regarding devices which contaminate the mains supply entering our houses, I decided to build a very simple outboard dc blocking distribution box for exactly that purpose. the schematic was courtesy of rod elliots excellent website and the components all courtesy of rs components so nothing to exotic, iec input from furutech and mains sockets from hpm. all blocking modules were assembled and slowly brought up to 240 volts using a variac as exploding capacitors are best not experienced and everything worked as hoped and after final assembly, rechecked again and soak tested under load. all good.

2 types of use were envisaged, for visual components and for audio.

firstly, dc voltage on the ac line is very common these days as components using switch mode power supplies have a degree of cause and even more recently, solar panelling and the associated inverters. dc on the ac line has a tendency to cause transformers to run hotter and noisier being the main issue.

on the visual side when inserting this device in line with the mains supply to the plasma we have at home showed a quite remarkable improvement in picture colour, stability of image, white noise level or blackness depth and the amount of heat generated from a 5yr old NEC50 plasma. can't watch anything now without it being in line. the depth of the black's reminded me of the best pioneer plasma's and I would not be surprised if their reputation was based on an internal dc blocking device as the effect on the black's and colour intensities was certainly similar.

as for sound reproduction on a modest system, the results were likewise positive with a quieter background noise being most evident and with transformers running considerably cooler.

more listening to be done but at this stage, all very positive.

cheers, g.

--- End quote ---

URL: http://www.stereo.net.au/forums/index.php?/topic/62465-d-c-blocking-on-mains-supply/
Pics attached.

Now, questions to our competent techies here, is it worth doing? How much would it cost? I am seriously interested to get one if it's effective. My AC mains here is sh!te.

Thanks,
William

Jehuty:
And I think this is the link to the schematics: http://sound.westhost.com/articles/xfmr-dc.htm

stevenvalve:
I find that most, if not all of these devices clean up the power, resulting in lower noise floor but at a cost of body and warmth, often the sound becomes a little more sterile and opaque. Using Diodes is also a problem. In a superbly well tuned system, i find its nearly always a backward step.

vitavoxdude:
Interesting that removing DC from the mains which could saturate your mains power feed strangling it removes some body and warmth; but not surprising in a finely tuned system where the slightest change is audible, for most other folk with less highly tuned Ferrias then your milage may vary.

For most I'd suggest the changing of a single resistor would hardly be audible either, not saying that its not the case but bear in mind that a saturated magnetic core in a power transformer with reduce the ability of your power supply to remain doing its job, fine with non demanding music but sad with large scale music which would hit the end stops.

In the majority of cases people who have shop bought equipment I can well imagine benefits to ridding DC via the caps and diodes approach; in all valve systems where signals are kept pure, the placing of any solid state switching diodes have got to be bad hence why SV reports a loss possibly, at least this makes sense to me. ::)

Jehuty:
Fair enough guys. Thanks for sharing your experience. I just thought that if it negatively affects my system then I'll just use it for my plasma TV.


--- Quote ---on the visual side when inserting this device in line with the mains supply to the plasma we have at home showed a quite remarkable improvement in picture colour, stability of image, white noise level or blackness depth and the amount of heat generated from a 5yr old NEC50 plasma. can't watch anything now without it being in line. the depth of the black's reminded me of the best pioneer plasma's and I would not be surprised if their reputation was based on an internal dc blocking device as the effect on the black's and colour intensities was certainly similar.
--- End quote ---

Still waiting on Zen's response. I'm keen to get one...  :)

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