DC Blockers - DIY effective and simple.

[mwhouston]

There are lots of info on DIYaudio website regard the schematic and also already made PCB. My understanding is that the voltage rating of the cap can be as low as 6 V but must be low esr and high current rating to withstand the inrush of large power amp.

I rarely use a PCB. in audio I believe they dull the sound. Fortunately most of my builds are valve amps all point-2-point or even better component-2-component (something I think I perfected if not invented). Why you would use a PCB for a DC blocker is beyond me but then the thought of a God baffles me too. You have seen my DC blocker internals. There is just a few large components, why a PCB?

My blocker will handled a 2200W electric jug. I have demonstrated this. How thick do the tracks of a PCB have to be to handle 10A? All my wiring is 10A rated. No PCB.

[Zaphod Beeblebrox]

I rarely use a PCB. in audio I believe they dull the sound. Fortunately most of my builds are valve amps all point-2-point or even better component-2-component (something I think I perfected if not invented). Why you would use a PCB for a DC blocker is beyond me but then the thought of a God baffles me too. You have seen my DC blocker internals. There is just a few large components, why a PCB?

PCB techniques do not "dull the sound" (provided they have been designed properly). In fact, without PCB systems, modern electronics, which operate in the GHz range would be impossible. Even better, using a PCB allows for absolute unit to unit consistency. That said, PCBs may not be required for extremely simple and/or low performance products, or those products whose production runs are very small.

 

My blocker will handled a 2200W electric jug. I have demonstrated this. How thick do the tracks of a PCB have to be to handle 10A? All my wiring is 10A rated. No PCB.

For the industry standard, 1 ounce copper (34um), a track width of 2500um will handle 10 Amps @ 50 degrees C.

For 2 ounce copper (68um), a track width of 1600um will handle 10 Amps @ 50 degrees C.

3 Ounce copper (which is more likely to be used in such an application), a track width of 1000um (1mm) will handle 10 Amps @ 50 degrees C.

More likely, however, a manufacturer will tend to use track widths of at least 5mm or more for such applications. So, even 1 Ounce copper is plenty. 2 Ounce copper, in such a situation will handle more than 40 Amps!

I should add here, that, although a jug element will provide a resistive load approaching 10 Amps, amplifiers can present far, far tougher loads. Peak inrush currents on many audio amplifiers (particularly those employing toroidal power transformers) can easily exceed 50 Amps.

Edited December 23, 2014 by Zaphod Beeblebrox

[mwhouston]

PCB techniques do not "dull the sound" (provided they have been designed properly). In fact, without PCB systems, modern electronics, which operate in the GHz range would be impossible. Even better, using a PCB allows for absolute unit to unit consistency. That said, PCBs may not be required for extremely simple and/or low performance products, or those products whose production runs are very small.For the industry standard, 1 ounce copper (34um), a track width of 2500um will handle 10 Amps @ 50 degrees C.For 2 ounce copper (68um), a track width of 1600um will handle 10 Amps @ 50 degrees C.3 Ounce copper (which is more likely to be used in such an application), a track width of 1000um (1mm) will handle 10 Amps @ 50 degrees C.More likely, however, a manufacturer will tend to use track widths of at least 5mm or more for such applications. So, even 1 Ounce copper is plenty. 2 Ounce copper, in such a situation will handle more than 40 Amps!

And the cost to produce? 8 leg tag strip for caps - $0.70.

Yes there is a place for PCBs. I have built dozens of PCB based devices. But fortunately not required for DC blockers, valve gear, Xovers, etc. Compare the number of solder joints of a PCB with component-2-component wiring. And the varying media the electrons have to course through.

[Black Orange]

I think cheap is good so no argument from me mr Houston. The only way I can make mine cheaper is to use all made in China, but unfortunately the only china made product I use is the internal earth tags. There will always be differences between approaches but I'm not prepared to loose my house over a HiFi power conditioning device. That's why they will be fully approved and the personal liability insurance cover we have wont be compromised. It is straight forward to do but expensive, sometimes it's better not to take the cheap approach. Different strokes, different folks.

 

Thats interesting Guru. After reading this I decided to get rid of all Made in China products which handles 240 volts in my house,well at least the one I can see... :

 

Kettle

Toaster

Sandwich press

Microwaves

Powerboards

Mobile Phone Chargers

Laptop Chargers

TV

Blu Ray players

Power amps

Sub woofer amp

Bluetooth Speaker

...................List goes on and on and on

 

Therefore I am sure you too would have got rid of all your Made in China products from your house as you are not prepared to loose your house over devices that may use made in China parts. 

 

Or are you just particular about Hi Fi and don't care about everything else in your house, as per your statement, every time you use these products you risk your house going up in flames. 

 

 

 

 

 

 

Edited December 23, 2014 by Black Orange

[pete_mac]

Mr Orange, you've misinterpreted what guru is saying.

 

He is referring to 'losing his house' in the context of being sued, not as a result of equipment which is 'made in China' catching on fire.

 

This is why guru is undertaking the certification process for this device.

[Guest guru]

well someone is going to have fun on the kerb outside your place today with all that out there. Christmas for them really came early. cheers Black Orange.

 

 

for what it's worth, we looked at sourcing chassis components through china manufacture and could have obtained cases from 83 cents to $7.90. consistency and finish were paramount for the price point we are charging and the samples we got didn't meet that requirement.

as for caps, it is almost impossible to get ripple current ratings for cheaper caps, we chose Vishay diodes out of Taiwan because there has never been a faulty one in the hundreds purchased.

the copper from the uk is bright and shiny which indicates them not using recycled copper.

you get what you pay for and as I charge a reasonable price for these, customers expect a very well made, safe product that wont have component pricing as the determining factor.

[Black Orange]

Mr Orange, you've misinterpreted what guru is saying.

 

He is referring to 'losing his house' in the context of being sued, not as a result of equipment which is 'made in China' catching on fire.

 

This is why guru is undertaking the certification process for this device.

 

Ok thanks for the clarification.

 

I believe Guru has sold many DC blockers to SNA members over the years. So to prevent loosing his house is he going to recall all those DC blockers and replace them with his new certified DC Blockers free of charge. 

 

If not...he still risks loosing his house. 

 

As a side note ...I honestly hate using my Kettle and other kitchen gadgets because of their, IMHO, less than stellar build quality, but I guess in today's worlds there isn't much else available.

Edited December 23, 2014 by Black Orange

[Guest guru]

I don't think years, maybe august was when I started building them and as for change over, no problems as they have no limits to the warranty, it is for their lifetime or mine ,whichever comes first. anyone who has one can return a pre certification unit for a certified unit any time they like. there for all to see in writing. cheers.

so far 2 sna members, woo hoo......

Edited December 23, 2014 by guru

[Black Orange]

I don't think years, maybe august was when I started building them and as for change over, no problems as they have no limits to the warranty, it is for their lifetime or mine ,whichever comes first. anyone who has one can return a pre certification unit for a certified unit any time they like. there for all to see in writing. cheers.

so far 2 sna members, woo hoo......

 

Genuine  . 

 

Although I suggest you proactively contact all members and swap over the units as that is the only way to completely cover yourself. Or at least start a new thread with a title recalling all your non certified blockers. 

[Black Orange]

The title of this thread clearly states DIY DC blockers. 

 

What has irked me is manufactures trying to undermine DIY jobs and peddle their products with statements like the one below. 

 

That's why they will be fully approved and the personal liability insurance cover we have wont be compromised.

 

When the newly certified manufacturer was himself selling DIY products (uncertified) I don't remember reading any comments about loosing the house or disclaimers regarding the dangers of DIY 240 volt products and the risks the buyers or for that matter the seller is taking.  

 

Lets leave this thread for the DIY'ers. Any constructive input is welcome but lets avoid the 'commercial confidentiality' statements and sales push.

 

Rant over. 

Apologies.

Edited December 23, 2014 by Black Orange

[Zaphod Beeblebrox]

Lets leave this thread for the DIY'ers. Any constructive input is welcome but lets avoid the 'commercial confidentiality' statements and sales push.

I presume your complaint applies equally to mwhouston? His units are also being built for profit.

[Guest guru]

i shall not say another word on the matter. ever. the commercial confidelity comment was a joke between andyr and myself and refers to a previous pm. if I relied on sales through stereonet, it would be a long time between drinks.

[skippy124]

As this thread was started as a DIY project, I would like to make some observations and comments on the design that has been posted, and DIY mains products in general.

DIY mains projects in general -

IMHO, anyone undertaking mains based DIY projects should have a basic understanding of the safety aspects/concepts of designing and constructing these types on equipment. Particularly the concepts of protective earthing, insulation, creepage and clearance, and component performance in manis applications. A good starting point in general is AS/NZS3100, and for this particular mains blocker, either AS/NZS3105 or AS/NZS3107 may specifically apply. @@guru may be able to comment on the applicable product safety standard.

Those undertaking these types of projects do so at their own risk - what they do cor themselves in the privacy of their own home is entirely up to them, but if a piece of "home grown" mains equipment is passed on to a third party, the risk stays with the maker. This risk includes abuse of the product by the third party that may result in a failure or dangerous situation occurring.

The DIY design that has been posted (and this is meant as constructive comment)

Firstly - the Rod Elliot link posted earlier describes the design of a DC blocker for inclusion inside an amplifier, and the design he finally presents is for an amplifier of up to 750VA max load, but with the proviso that the ripple current rating of the capacitor must be suitable This is consistent with the capacitors he has chosen, 4700uf 63v - where there are caps available that are rated at 3 amps or a tad more max ripple current.

The 4700uf 50V Jaycar caps are rated at 2.28 Amps max ripple current, and as such if using these the fuse used should be a 3 to 4 amp slow blow. Running a higher load than 500VA long term will result in premature capacitor failure. A short test at 2400VA does not give the whole picture, the caps may be able to pass a ripple current of 10 amps for a short to medium time, but they are operating at over 4 times their maximum rated ripple current. These caps will have a typical ESR of 50 to 70 milliohms (ESR is not published for these caps, even on the manufacturers spec sheet). At 50 milliohms ESR the cap will be dissipating 5 watts with a 2400VA load connected!

I would use a specific earth bonding point for the chassis with solder lugs for the incoming and outgoing mains cables earth wires, and use paint piercing screws combined with star washers specifically designed for earthing applications. An alternative method is to remove the paint around the earthing screw, but this is not visually attractive. Checking and earth bond with an ohmmeter shows whether there is contact or not, but does not show if the earth is capable of passing a fault current. This is normally done by passing a current of 7 to 10 amps from the earth pin on the lead to the chassis and measuring the voltage drop.

The caps should either be double insulated (this is mentioned in the article) or supported so that they can't move and come into contact with the chassis or cover - the insulating sleeve on the cap is not rated for mains voltage. Fixing the caps in place would also prevent the rear cap moving rearward and contacting the rear cover screw that looks to be close to it.

I would see if there is a more suitable housing. The one used does not provide a solid location for the front and rear panels, if there was tug of enough force on the input or output cable, the panel may bend out exposing the internal components/wiring, and in the case of the fuse on the rear panel it culd tilt it up towards the top of the cover. Also, how well is the top cover bonded to the bottom cover - Are theer any star washers used under the heads of the screws - there should be a specific mechanism/method for ensuring that the top cover is securely earthed to the chassis.

As stated above, these comments are meant to be constructive and are my opinions only.

I don't want to deter anyone from having a go at DIY, but just wanted to provide some basic cautions regarding the building of mains based equipment.

Cheers

John

[mwhouston]

Fortunately I have only sold two of the DC Blocker in original form and are about to make a forth (I have been using one for some time).

In the interest of public safety I will make "safer" units and replace, free of charge, those sold.

Part of the safer DC Blocker;

- use an heavy ABS enclosure
- use plastic cable glands instead of the nickel plated metal ones
- down grade the slow blow fuse to 4A
- add additional insulation to the caps
- secure the caps better
- ensure all small bolts and screws have spring washers
- etc.

Edited December 23, 2014 by mwhouston

[Black Orange]

As this thread was started as a DIY project, I would like to make some observations and comments on the design that has been posted, and DIY mains products in general.

DIY mains projects in general -

IMHO, anyone undertaking mains based DIY projects should have a basic understanding of the safety aspects/concepts of designing and constructing these types on equipment. Particularly the concepts of protective earthing, insulation, creepage and clearance, and component performance in manis applications. A good starting point in general is AS/NZS3100, and for this particular mains blocker, either AS/NZS3105 or AS/NZS3107 may specifically apply. @@guru may be able to comment on the applicable product safety standard.

Those undertaking these types of projects do so at their own risk - what they do cor themselves in the privacy of their own home is entirely up to them, but if a piece of "home grown" mains equipment is passed on to a third party, the risk stays with the maker. This risk includes abuse of the product by the third party that may result in a failure or dangerous situation occurring.

The DIY design that has been posted (and this is meant as constructive comment)

Firstly - the Rod Elliot link posted earlier describes the design of a DC blocker for inclusion inside an amplifier, and the design he finally presents is for an amplifier of up to 750VA max load, but with the proviso that the ripple current rating of the capacitor must be suitable This is consistent with the capacitors he has chosen, 4700uf 63v - where there are caps available that are rated at 3 amps or a tad more max ripple current.

The 4700uf 50V Jaycar caps are rated at 2.28 Amps max ripple current, and as such if using these the fuse used should be a 3 to 4 amp slow blow. Running a higher load than 500VA long term will result in premature capacitor failure. A short test at 2400VA does not give the whole picture, the caps may be able to pass a ripple current of 10 amps for a short to medium time, but they are operating at over 4 times their maximum rated ripple current. These caps will have a typical ESR of 50 to 70 milliohms (ESR is not published for these caps, even on the manufacturers spec sheet). At 50 milliohms ESR the cap will be dissipating 5 watts with a 2400VA load connected!

I would use a specific earth bonding point for the chassis with solder lugs for the incoming and outgoing mains cables earth wires, and use paint piercing screws combined with star washers specifically designed for earthing applications. An alternative method is to remove the paint around the earthing screw, but this is not visually attractive. Checking and earth bond with an ohmmeter shows whether there is contact or not, but does not show if the earth is capable of passing a fault current. This is normally done by passing a current of 7 to 10 amps from the earth pin on the lead to the chassis and measuring the voltage drop.

The caps should either be double insulated (this is mentioned in the article) or supported so that they can't move and come into contact with the chassis or cover - the insulating sleeve on the cap is not rated for mains voltage. Fixing the caps in place would also prevent the rear cap moving rearward and contacting the rear cover screw that looks to be close to it.

I would see if there is a more suitable housing. The one used does not provide a solid location for the front and rear panels, if there was tug of enough force on the input or output cable, the panel may bend out exposing the internal components/wiring, and in the case of the fuse on the rear panel it culd tilt it up towards the top of the cover. Also, how well is the top cover bonded to the bottom cover - Are theer any star washers used under the heads of the screws - there should be a specific mechanism/method for ensuring that the top cover is securely earthed to the chassis.

As stated above, these comments are meant to be constructive and are my opinions only.

I don't want to deter anyone from having a go at DIY, but just wanted to provide some basic cautions regarding the building of mains based equipment.

Cheers

John

 

I had decided not to comment on this thread further but I had to just to say thanks for the above.

Very helpful and I am sure the DIY community (of which I am not a part of) will be much safer because of your input.

[Black Orange]

I presume your complaint applies equally to mwhouston? His units are also being built for profit.

 

Of course. I am happy for the DIY'ers to take risk and burn down their house but when these items are being sold all involved must know the risks.

 

I am glad mwhouston is following Guru and will be replacing the sold units for safer models.

[mwhouston]

The new, supposedly safer, DC Duffer. Polycarb enclosure with only metal screws protruding from the bottom of the enclosure. Both screws have spring washers and are earthed. Fuse is now 4A slow blow. No more fancy nickel plated cable glands but plastic ones but still includes the RFI\EMI filter and ferrite chokes. 10A ratted power lead.

[mwhouston]

A flock of blocker to replace the metal case versions. In total I have just completed five of these. Along the way I sold two more that is why so many.

Edited January 12, 2015 by mwhouston

[mwhouston]

A SNA member recently bought one of my newer and safer DC blockers. He was suffering buzzing from a high-end power board. Though I said I was not sure it would fix the buzzing it appears I has to quite a large degree.

 

I have his permission to reprint his comments from a PM here:

 

"Yes. It did reduce the a lot of the buzzing from the isotek polaris power strip.  There is minimal buzz but its no where as loud as it used to be.  Previously i could hear it a meter away, now i would have to very carefully listen to it  This was from listening to my system in the afternoon.

 

I also listened to it critically last night when I had the dimmers on from both rooms - same conclusion, hardly noticed any buzzing noise.  Happy to conclude that it worked, and worked quite well.

As for the changes or improvement in sound, I thought that the soundstage height and depth improved a bit.  Also, the sound was a bit smoother in the mids and highs but this is not blind tested, so take it with a grain of salt.

 

Overall, quite happy with it for the reasons that it solved the DC issue i had, the sonic improvement was a nice bonus.."

 

[Red MacKay]

Best I pull my finger out then and get my new unit going for in a couple of weeks when you are here!

 

It will be mighty interesting plugging your unit into my system and seeing/ hearing the results.

[Addicted to music]

A flock of blocker to replace the metal case versions. In total I have just completed five of these. Along the way I sold two more that is why so many.

Jihad devices for DC...

[andyr]

Jihad devices for DC...

 

Haha - aptly put, Peter! :lol:

 

Andy

[Guest Muon]

Having a very small budget I have one of the diyhifisuppy blockers coming (that seem to have been discontinued), will it be enough? I'm not sure and truth be told I have not had the buzzing transformer since rearranging the position of the phono PCB in the case. Maybe it wasn't DC in my case after all

 

These things are wired into the neutral line from the iec socket, is this correct?

[mwhouston]

I do not "wire" mine into the the neutral line and do not use IEC sockets.

Edited January 20, 2015 by mwhouston

[Guest Muon]

I do not "wire" mine into the the neutral line and do not use IEC sockets.

That is because you make a separate unit, this is wired into the device.

 

Edit: seems i should have posted in a different thread.

 

Hmm..according to a thread on diyaudio it doesn't matter if It's the hot or neutral and will work the same either way. Though the manufacturer says the neutral so I'll go with that when it arrives.

Edited January 20, 2015 by ortofun