Hi Andrew, the capacitors do not pass that much current at 1V4 drop across them and the diodes does not pass that much current at mains voltage either.
Power dissipation for each diode is 0.7V at a current of what, 3 amp? Which is relatively low. The diode at peak non repetitive current rating will cater for inrush adequately. A 1N5408 can pass a peak non repetitive current for one half cycle at mains of 200A.
Nico
Power dissipation for each diode is 0.7V at a current of what, 3 amp? Which is relatively low. The diode at peak non repetitive current rating will cater for inrush adequately. A 1N5408 can pass a peak non repetitive current for one half cycle at mains of 200A.
Nico
Hi Nico,
I too use 1n5402 or 4 for this bypass of DC blocking.
The diodes only pass current (bypass) when the voltage across the capacitors exceeds ~400mV.
This can only happen when a current surge passes through.
This current surge is most likely during fault condition or at start up. Both very short term occurrences.
For all "normal" amplifier operation the capacitor impedance should be selected such that the maximum operating current passes through the caps and not the diodes.
If the capacitors and the diodes are chosen correctly then the diodes rarely pass current and so the pulse current capability of diodes can be used when assessing diode size.
I guess that puts us in agreement.
I too use 1n5402 or 4 for this bypass of DC blocking.
The diodes only pass current (bypass) when the voltage across the capacitors exceeds ~400mV.
This can only happen when a current surge passes through.
This current surge is most likely during fault condition or at start up. Both very short term occurrences.
For all "normal" amplifier operation the capacitor impedance should be selected such that the maximum operating current passes through the caps and not the diodes.
If the capacitors and the diodes are chosen correctly then the diodes rarely pass current and so the pulse current capability of diodes can be used when assessing diode size.
I guess that puts us in agreement.
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This isn't my DC Blocker resp. my favorite topology.
Two topologies I like more than all the others:
1) that one about
http://www.scintilla-buizenversterk...erkers/zelfbouw/zelfbouw sites/DC-Blocker.htm
2) that one about
http://www.lcaudio.com/index.php?page=316
3) that one by post #33 (my own idea, but still not tested) about
http://www.diyaudio.com/forums/powe...buzzing-toroid-transformers-what-right-4.html
For the circuits number 2) and 3) I am looking to high power rectifier diodes, where the forward voltage drop is below 0V3 (like usual at very small signal germanium diodes) for the reverse polarity voltage of the electrolytic cap (I think, 0V3 highest reverse voltage is better for the cap than above 0V6, as usuall by normal rectifier silicon diodes and zeners in reverse direction. Please note: by the circuit under number 3) only one diode should have this lower value for the forward voltage drop !!!
BTW - read Bob Cordell's comments about
http://www.diyaudio.com/forums/powe...buzzing-toroid-transformers-what-right-4.html
carefully
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Tief, there are numerous data sheets around the capacitor supply industry that talk about back to back, but nothing much about theory or research. From what I can see its an industry practice that's was invented before Noah had a boat.
I just use it to install polarised electrolytic's in a non-polarised application; sorry but I'm not that interested in researching the pros & cons. It works, that's me done.
I just use it to install polarised electrolytic's in a non-polarised application; sorry but I'm not that interested in researching the pros & cons. It works, that's me done.
Essay's about Magnetostrictive Vibration under non-sinusoidal magnetizing condition
Now an other topic (see headline) - generals (basics) for the reasons for mechanical humming/buzzing:
in the reference list (bibliography) on page 7 about
http://www.dalitech.com/Resources/Measuring Acoustic Noise Emitted by Power Transformers.pdf
I found this papers:
1) IEEE Xplore - Sign In
Who can upload this?
see also
Structure of materials: an ... - Google Bücher
and
Evaluation of Barkhausen Noise and Magnetoacoustic Emission Signals Properties for Plastically Deformed Armco Iron
After calling with several capacitor manufacturers I came to the conclusion, that custom made bi-polar versions here definitely the best solution.
Now an other topic (see headline) - generals (basics) for the reasons for mechanical humming/buzzing:
in the reference list (bibliography) on page 7 about
http://www.dalitech.com/Resources/Measuring Acoustic Noise Emitted by Power Transformers.pdf
I found this papers:
1) IEEE Xplore - Sign In
Who can upload this?
see also
Structure of materials: an ... - Google Bücher
and
Evaluation of Barkhausen Noise and Magnetoacoustic Emission Signals Properties for Plastically Deformed Armco Iron
To me this is not enough.
The decisive factor is whether it works without dynamic losses while sonic transmission.
I ask "FTcap" in this case, and I get the information, that a "back to back" serial connection isn't the royal way. The royal way would be to order real bipolar caps with screw terminals, because the parameters of such a capacitor are much more better in all respects than two caps connected in "back to back".
This brings me to the question, how the follow companies realize their dc filters:
1) :: VIBEX :: (DC filter Two 1R)
http://www.khonkaenlink.info/share/image.php?id=9A83_4E034839&jpg
2) http://www.kempelektroniks.nl/Files...pdf_ps_power_dc_x_terminator_en_plus__eng.pdf (DC X Terminator)
Kemp DC X-Terminator Plus Mains Filter at Audio Affair
Kemp Elektroniks - Power DC X-terminator
Perhaps one of you can upload the associate schematic diagram.
Attachments
Tief, you obviously have a personal mission to investigate this issue
Please let us all know when you have finished this important work & why our back to back polarised capacitors are in mortal danger.
Please let us all know when you have finished this important work & why our back to back polarised capacitors are in mortal danger.
I myself have no experience with all this things and therefore I am dependent of the manufacturer's statements (and the statements from the members here). And in the meantime my conclusion is follow: The use of humfree toroidals like those from the brands "Plitron" or "Tauscher" instead the use of additional DC filters.
The individual production of a new transformer and the follow exchange is still cheaper than retrofitting an external DC-filter like the ones I have mentioned in post # 227 (even for large 1 KVA versions). Thus all the DC filter unit overviews - I have ask before on various threads of the topic "DC filter" like
http://www.diyaudio.com/forums/pass-labs/104491-dc-blocker-test-report.html
http://www.diyaudio.com/forums/solid-state/2080-dc-filter.html
http://www.diyaudio.com/forums/powe...t-buzzing-toroid-transformers-what-right.html
http://www.diyaudio.com/forums/power-supplies/104626-dc-blocking-filter-mains.html
http://www.diyaudio.com/forums/solid-state/189009-dc-blocker-diode-cap-orientation.html
http://www.diyaudio.com/forums/power-supplies/104626-dc-blocking-filter-mains.html
http://www.diyaudio.com/forums/pass-labs/21487-noise-transformer.html
are no longer of interest for me.
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Hi Tief,
If you prefer the results of using those two manufacturers, then go ahead. We have heard the recommendation.
For the rest of us who realise why the DC blocker is required and how to implement it, then let us get on with the discussion and you
If you prefer the results of using those two manufacturers, then go ahead. We have heard the recommendation.
For the rest of us who realise why the DC blocker is required and how to implement it, then let us get on with the discussion and you
can be implemented at any time of your choosing.
Tief, good luck with your project
But in my experience during my professional work life I lead a team that had to make equipment that was virtually silent. Our process required actual noise levels from suppliers such as transformer manufacturers. The 2x you mention are renowned for their low noise, but silence does not exist in the transformer world I am afraid to say.
However mains borne DC on the line does make even these quiet transformers hum. So a DC filter does have a place for some people in their applications. Thankfully retirement has allowed me the time to experiment (play) with my system & am pleased to say I am satisfied, so I & am finished.
But in my experience during my professional work life I lead a team that had to make equipment that was virtually silent. Our process required actual noise levels from suppliers such as transformer manufacturers. The 2x you mention are renowned for their low noise, but silence does not exist in the transformer world I am afraid to say.
However mains borne DC on the line does make even these quiet transformers hum. So a DC filter does have a place for some people in their applications. Thankfully retirement has allowed me the time to experiment (play) with my system & am pleased to say I am satisfied, so I & am finished.
Therefore I start this thread:
http://www.diyaudio.com/forums/powe...t-buzzing-toroid-transformers-what-right.html
Most of this design's you will find there.
After several conversations with manufacturers of elektrolytics I always got the same information:
Be sure to avoid a "back-to-back" topology for create an unipolar cap (otoh - in most commercial amps such topologies are in use obviously without trouble). But an unipolar cap exist not as standart part by this values for the capacity. Thus one must order such a part as custom made.
O.K. - but what is the right topology?
I'm still very confused about the wide range of different opinions and circuit topologies, particulary the different kinds of the electrolytic connections.
Yes, and for this reason I will investigate in the next time the values for voltages and currents, that are necessary for generating buzzing effects at various torodials.
For me it will be very intersting to know the DC values at the mains (both in various aeras in Germany and anywhere in the world), that usually occur as a maximum value. And in addition the frequency of DC contamination (because that is not a permanent but only a temporary unwanted effect).
Are there studies about this ??
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But he does not want to understand the need. He has already decided that his questioning have led him to the correct conclusion and as a result
Tief, I think you have caught the cat by its ***. This problem is not a country or world wide phenomena it is usually as close as your own home. The simple fact that your wife uses her hairdryer at half speed shifts the mains a little, it definitely would not shift the main grid in Germany.
The reason is simply because your home is decoupled from the main grid by some resistance (the wire) and the DC off-sett is mostly confined to your own environment or another environment that is sufficiently close to yours to cause such interference.
The reason is simply because your home is decoupled from the main grid by some resistance (the wire) and the DC off-sett is mostly confined to your own environment or another environment that is sufficiently close to yours to cause such interference.
You must read my comments more exactly.
If you have the choice between this two options
Vibex V1R, 1100,-- Euro
Vibex V1R DC Power Filter - News von Audio Equipment Mauritz.
Gaudios - Vibex - ONE, TWO, THREE
Dinew High Fidelity ● Vibex Reference 6 Rhodium Netzleiste
Power DC X Terminator, 495,-- Euro
Kemp Elektroniks DC X-Terminator PLUS - 1 Piece
http://www.kempelektroniks.nl/Files...pdf_ps_power_dc_x_terminator_en_plus__eng.pdf
and the humfree toroidal transformer version for approximately 400 Euro,
what would you do by your amp, if there was inside a toroidal with mechanical humming by present DC on the mains?
Then the "switch off" of the hairdryers and similar stuff in my home blown away all such problems.
And why exist this essay ??
http://www.dalitech.com/Resources/Measuring Acoustic Noise Emitted by Power Transformers.pdf
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