Author Topic: DC blocking on mains supply  (Read 7463 times)

Offline Jehuty

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DC blocking on mains supply
« on: March 01, 2014, 01:35:45 PM »
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.

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
Not all that matters can be measured, not all that can be measured matters.

Offline Jehuty

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Re: DC blocking on mains supply
« Reply #1 on: March 01, 2014, 01:45:15 PM »
And I think this is the link to the schematics: http://sound.westhost.com/articles/xfmr-dc.htm

Not all that matters can be measured, not all that can be measured matters.

Offline stevenvalve

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Re: DC blocking on mains supply
« Reply #2 on: March 01, 2014, 03:57:53 PM »
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.
« Last Edit: March 01, 2014, 04:03:13 PM by stevenvalve »

Offline vitavoxdude

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Re: DC blocking on mains supply
« Reply #3 on: March 01, 2014, 05:57:35 PM »
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. ::)
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline Jehuty

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Re: DC blocking on mains supply
« Reply #4 on: March 01, 2014, 08:16:45 PM »
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.

Still waiting on Zen's response. I'm keen to get one...  :)
Not all that matters can be measured, not all that can be measured matters.

Offline zenelectro

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Re: DC blocking on mains supply
« Reply #5 on: March 05, 2014, 03:39:38 PM »
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.

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

WRT Stevens response, this is not a power filter but a DC blocker. It could well improve the sound if there is any DC on mains.
The caps on that schematic look too small to me. At a guess I'd say 10,000uF each minimum they would also have to have high
current rating.

WRT Vitas response, the diodes in normal use never switch on or off. They are just for turn on / off so the caps don't
have their voltage exceeded.

To make this properly I'd be using a lot bigger diodes and high spec caps.

Also not sure what the legalities are WRT this sort of thing.

Having said this, they do uses back to back diodes for safety ground lifting in many commercial products so I'm sure it's
legally doable with the right spec bits. 

cheers

Terry

Offline stevenvalve

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Re: DC blocking on mains supply
« Reply #6 on: March 05, 2014, 04:08:32 PM »
this is not a power filter but a DC blocker. Yes I read that, I am saying anytime I have played with any electronic devices on the mains and it has always (except your mates power conditioner) been a backward step, maybe this is worth making.
« Last Edit: March 05, 2014, 04:10:07 PM by stevenvalve »

Offline guru

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Re: DC blocking on mains supply
« Reply #7 on: July 24, 2014, 10:50:17 PM »
I saw this thread ages ago but decided not to reply until I had made more of the blockers to use on a complete system and get an idea as to what type of sound using these devices would generate. the first thing you notice is how extended the bass is and how dynamic the sound is. transient speed and attack on piano recordings like bugge wesseltoft's "duo" is sensational, spatial cues just make you smile. the entire presentation of the music is changed, for the better. there is a layer of noise removed from the system that you never realised was there until its gone is the best way of describing the effect. the modules cost $20 in parts [2 capacitors and 4 diodes] and there is no downside that I can hear so if you are technically capable then I think it is the best audio upgrade I have heard.
regards, g.

Offline ozmillsy

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Re: DC blocking on mains supply
« Reply #8 on: July 25, 2014, 07:25:26 AM »
Thanks for the feedback Guru.    Can you clarify the parts list (values used, etc).

If a few people wanted to try these,  are you prepared to assemble some and pass them on,  at a price that recovers your time/costs?

I can solder.  But I have a question mark over my competency.      :-[
It's all about the music,, not the equipment.

Offline guru

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Re: DC blocking on mains supply
« Reply #9 on: July 25, 2014, 10:57:39 AM »
the parts are straight forward and readily available from rs components, they are the same as in the final schematic in rod elliots article, 2 x 63v/4700uF caps and 4 x 1N5404 Diodes. the ones I make up use a high quality Japanese made chassis, furutech IEC socket inlet and a specialised HPM mains outlet and Audio Note copper or silver mains cable internally. the parts cost is for a 2 socket outlet is $40 for the modules [caps and diodes] $70 for the case, $44 for the inlet socket, $28 for the outlet sockets, $50 for the copper wires and around 3 hours to fabricate them up so that's it in a nutshell.
we are contemplating going for certification in order to retail them but until that happens, won't be selling them. they are safe and so far have about 800 hours up on mine and all good. this is not something I would be attempting with out a fair sense of knowledge about construction and mains so knowing how to solder is good but it needs more than that. if you want to borrow one then let me know and you can see what it does in your system to see if it's worth pursuing for you.
regards, g.

Offline ozmillsy

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Re: DC blocking on mains supply
« Reply #10 on: July 25, 2014, 11:39:36 AM »
this is not something I would be attempting with out a fair sense of knowledge about construction and mains so knowing how to solder is good but it needs more than that.
Yes, exactly.   

Quote
if you want to borrow one then let me know and you can see what it does in your system to see if it's worth pursuing for you.
That would be great,   thanks.   I'll shoot you a PM.
It's all about the music,, not the equipment.

Offline Tuyen

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Re: DC blocking on mains supply
« Reply #11 on: July 25, 2014, 05:07:28 PM »
You guys been powering your whole system with a power board that is plugged straight into wall socket??   :o

Had assumed most on here would have either isolation/balanced transformers or power conditoner/regenerator...      Mario swore by his BlackBox (isolation tran/conditioner) while Bryan said he couldn't live without his ExactPower EP15a power regenerator.    Both these things would take out the DC from the incoming feed into your components power transformer..

Another option is the DC Blokker modules from DIYhifisupply.  Install that in components.
http://www.hificollective.co.uk/components/diyhifisupply_dcblokker.html
http://www.acoustic-dimension.com/DHS-modules/DIY-HiFi-Supply-DC-blokker.htm

Either way, I can't more highly recommend investing some money in either some form of beefy balanced/isolation transformer or power conditioner/regenerator.    The difference (usually an improvement) is often quite substantial :)

Offline Jehuty

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Re: DC blocking on mains supply
« Reply #12 on: July 25, 2014, 07:30:11 PM »
You guys been powering your whole system with a power board that is plugged straight into wall socket??   :o

I blame Stevenvalve. He reckons they're all evil  :P
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Offline ozmillsy

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Re: DC blocking on mains supply
« Reply #13 on: July 25, 2014, 07:34:11 PM »
Tuyen, yes.

But I dont think I have used a device that claimed to *only* do DC blocking,  and absolutely nothing else.

Sometimes less is more.
It's all about the music,, not the equipment.

Offline vitavoxdude

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Re: DC blocking on mains supply
« Reply #14 on: July 25, 2014, 08:46:09 PM »
Yes, generally I'd agree with SV that placing devices upstream of top quality equipment may result in degradation, however this is probably due in no small part to increasing the impedance of the supply. DC blockers will improve a supply where DC is saturating the transformer of the PS where the design is not over engineered by a factor of at least 4.  Properly sorted PS where a large reserve of clean supply current is available may well sound better without upstream devices; after all we can hear the differences better power cables bring right!

I personally go for isolation transformers on each device, but not Krells and the like due to the current demands.  Galvanic isolation is all good as far as I am concerned.  Trying to keep a clean 240 volt supply for audio is not an easy task as it is contaminated with lots of unwelcome dross.  If you have to money, I'd recommend going for the big PS audio mains purifier in its handsome box, its fully certified and all the hard work is done for you.

My vote therefore goes to having them as being generally better than not BUT any device hooked into the mains needs to meet minimum voltage ratings or else insurance may be voided.  Don't overlook this.

V
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline ozmillsy

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Re: DC blocking on mains supply
« Reply #15 on: July 25, 2014, 09:53:54 PM »
I'm a fan of trying things, not just talking about them.

Full credit to Guru for offering to loan this device out at no cost or obligation. [Thumbs up]
It's all about the music,, not the equipment.

Offline hedalfa

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Re: DC blocking on mains supply
« Reply #16 on: July 25, 2014, 11:44:19 PM »
I'm a fan of trying things, not just talking about them.

Full credit to Guru for offering to loan this device out at no cost or obligation. [Thumbs up]

I second that, Guru has made a very helpful and generous offer to try out the device.

Offline guru

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Re: DC blocking on mains supply
« Reply #17 on: July 26, 2014, 12:12:40 AM »
thank you but it's fine, I have multiple versions I have fabricated up to use in the various systems I have so you are not causing any issue for me. you just have to be careful not to scratch the casework of the boxes as it's easily marked being brushed aluminium and not cheap.

Offline Jehuty

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Re: DC blocking on mains supply
« Reply #18 on: December 06, 2014, 08:25:08 AM »
the parts are straight forward and readily available from rs components, they are the same as in the final schematic in rod elliots article, 2 x 63v/4700uF caps and 4 x 1N5404 Diodes. the ones I make up use a high quality Japanese made chassis, furutech IEC socket inlet and a specialised HPM mains outlet and Audio Note copper or silver mains cable internally. the parts cost is for a 2 socket outlet is $40 for the modules [caps and diodes] $70 for the case, $44 for the inlet socket, $28 for the outlet sockets, $50 for the copper wires and around 3 hours to fabricate them up so that's it in a nutshell.
we are contemplating going for certification in order to retail them but until that happens, won't be selling them. they are safe and so far have about 800 hours up on mine and all good. this is not something I would be attempting with out a fair sense of knowledge about construction and mains so knowing how to solder is good but it needs more than that. if you want to borrow one then let me know and you can see what it does in your system to see if it's worth pursuing for you.
regards, g.

Hi guru,

May I know if you have started selling the DC blocker? I'm really keen to get one but I'd like to try one in my system first.

Thanks,
Wil
Not all that matters can be measured, not all that can be measured matters.

Offline rab

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Re: DC blocking on mains supply
« Reply #19 on: December 06, 2014, 01:31:55 PM »
i'm interested, too (but in Melbourne  :-[).

Do we have any idea of cost?