Correct Fitting of DC Blockers

astrouk1 · 21st July 2012, 06:52 PM

Hi Everyone,

I've got one of these DC Blockers from DIY HiFi Supply, I find the fitting description quite confusing, it says in the instructions to put it on the neutral side, yet in the picture it appears to be on the live/hot side:

DC Blokker Module | Diy HiFi Supply

Does anyone have any advice on which is the correct side to fit the blocker?

Many thanks for any assistance.

richie00boy · 21st July 2012, 07:15 PM

It does not matter as it is a series circuit.

astrouk1 · 21st July 2012, 09:05 PM

Many thanks, I'll get building!

grommeteer · 21st July 2012, 10:02 PM

Does anybody know what hides in the mold?

DF96 · 22nd July 2012, 06:07 PM

Capacitor and/or some diodes.

grommeteer · 22nd July 2012, 08:55 PM

I am not going to build one as I do not think a few volts of DC are going to saturate my transformer. But would it not take a C in the range of 1000s of uF to keep voltage drop low? And can you please explain how diodes can help? Antiparallel? Isn't that just subtracting 0.7V in both polarities? I read about a DC eliminating device by Burmester that involved a lot of semis and also claimed to lower the impedance!! of the mains. It was said to load the mains during the bigger half wave. A giant "AC shunt regulator".

DF96 · 22nd July 2012, 09:05 PM

Yes, big caps are needed so back-to-back electrolytics with steering diodes is one option. Some people claim that a simple shorted bridge (so two diode drops) is sufficient on its own, but I am not convinced. I think if I needed a DC blocker I would use a biased electrolytic, with bias obtained from the AC supply.

A few volts of DC could disturb a low resistance transformer, like some toroidals. Remember, all DC sees is the primary resistance and there is no cancelling current in a secondary to reduce DC flux.

dangus · 23rd July 2012, 12:51 AM

I think it falls into the category of devices that work equally well whether you wire them into a circuit or leave them in the box.

ChrisA · 23rd July 2012, 03:54 AM

Quote:

Originally Posted by astrouk1

Hi Everyone,

I've got one of these DC Blockers from DIY HiFi Supply

Maybe a good idea might be to MEASURE the amount of DC current in your mains wall outlets before investing in a large capacitor.

Even if there were a few milliamps of DC the effect is only that the effective size of the power transformer is reduced

The next question is if these things are even legal. Seriously. I doubt it is an X or Y rated cap and I _think_ (?) it needs to be if it is connected to the primary side of a transformer. Or is that only if the cap is in parallel and this is series?

Next, I wonder what problems this might introduce. With the primary you now have a series LC. Will it oscillate? What about inductance of the cap and ESR?

One other question. Every large cap has a rating for max "ripple current". I wonder what is the rating of the cap inside the box. Certainly being connect in series with the mains it will see "ripple" (that is kind of an understatement)

ChrisA · 23rd July 2012, 03:59 AM

Quote:

Originally Posted by dangus

I think it falls into the category of devices that work equally well whether you wire them into a circuit or leave them in the box.

No, I'm thinking it might be measurably better to leave it in the box. This gadget is basically a "high pass filter".

21st July 2012, 06:52 PM	#1
astrouk1 diyAudio Member Join Date: Aug 2010	Correct Fitting of DC Blockers Hi Everyone, I've got one of these DC Blockers from DIY HiFi Supply, I find the fitting description quite confusing, it says in the instructions to put it on the neutral side, yet in the picture it appears to be on the live/hot side: DC Blokker Module \| Diy HiFi Supply Does anyone have any advice on which is the correct side to fit the blocker? Many thanks for any assistance.

21st July 2012, 07:15 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	It does not matter as it is a series circuit. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
2 oHm bass blockers	3025826	Car Audio	3	1st March 2012 11:32 PM
Homemade Bass Blockers	englishjg	Parts	2	10th September 2008 04:05 AM
Dc-detection, is this correct?	fixation	Solid State	12	16th February 2006 07:08 PM
problem with bass blockers	all_about the12	Car Audio	1	15th October 2004 03:08 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

21st July 2012, 09:05 PM	#3
astrouk1 diyAudio Member Join Date: Aug 2010	Many thanks, I'll get building!

21st July 2012, 10:02 PM	#4
grommeteer diyAudio Member Join Date: Apr 2012 Location: Kiel, Germany	Does anybody know what hides in the mold?

22nd July 2012, 06:07 PM	#5
DF96 diyAudio Member Join Date: May 2007	Capacitor and/or some diodes.

22nd July 2012, 08:55 PM	#6
grommeteer diyAudio Member Join Date: Apr 2012 Location: Kiel, Germany	I am not going to build one as I do not think a few volts of DC are going to saturate my transformer. But would it not take a C in the range of 1000s of uF to keep voltage drop low? And can you please explain how diodes can help? Antiparallel? Isn't that just subtracting 0.7V in both polarities? I read about a DC eliminating device by Burmester that involved a lot of semis and also claimed to lower the impedance!! of the mains. It was said to load the mains during the bigger half wave. A giant "AC shunt regulator".

22nd July 2012, 09:05 PM	#7
DF96 diyAudio Member Join Date: May 2007	Yes, big caps are needed so back-to-back electrolytics with steering diodes is one option. Some people claim that a simple shorted bridge (so two diode drops) is sufficient on its own, but I am not convinced. I think if I needed a DC blocker I would use a biased electrolytic, with bias obtained from the AC supply. A few volts of DC could disturb a low resistance transformer, like some toroidals. Remember, all DC sees is the primary resistance and there is no cancelling current in a secondary to reduce DC flux.

23rd July 2012, 12:51 AM	#8
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	I think it falls into the category of devices that work equally well whether you wire them into a circuit or leave them in the box.