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Glen B 14th May 2011 05:29 PM

DC blocker diode/cap orientation
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I know there are a lot of threads on mains DC blocking, but none I've seen address my specific question. Circuit #1 is used in a popular manufacturer's amps to block DC. I have been told that the orientation of the diodes vs caps is incorrect, that there is no protection for the caps the way it is now. Drawing #2 shows the caps reversed. Which is the right way ? Comments ?

djk 14th May 2011 11:36 PM

tiefbassuebertr 19th August 2011 06:49 PM

a good Question. Here the overview of the threads, that I know:
My favorites are the follow topologies:
DC-Blocker - Scintilla-buizenversterkers (correct version from picture two in post #1)
L C Audio Technology / DC Filter
Because I don't understand the LC topology exactly, I ask there.
Actually there are caps necessary with reverse voltage above 1V. MKP (foil) versions unfortunately very large and expensive.

more threads outside diyaudio: (many schematics and topologies)

Plitron's approach:

To get more informations from the web arround this topic I must know all the usual terms of this unit.
There are a wide range of terms; "DC-Blocker" "Toroidal Noise Filter (Cancellator)" and "Humbuster" are only three. Who knows more terms for this unit (for google search)?

tiefbassuebertr 21st August 2011 10:08 AM

by using the circuit about
DC-Blocker - Scintilla-buizenversterkers
4 pcs single diodes are necessary instead one bridge rectifier.

tiefbassuebertr 22nd August 2011 05:46 PM

I'm curious how many threads still exist here on diyaudio associated with DC- filters and DC- blockers for toroidal power transformers.
Here again is one, that is worth mentioning, too (especially post #11, written by diyaudio member "paulmc", Chief Executive Officer = CEO by PS-Audio) :

ken chaffee 27th December 2014 02:14 PM

Electrolytic Caps
Please do not connect electrolytic capacitors across an AC power source as shown in the drawing. They will explode I have been in electronics and electrical work for over 30 years and speak from experience.

dragonweed 27th December 2014 04:45 PM

Those electrolytics on the schematics above are not connected ACROSS the AC power source..... The max. voltage will be present on them is about 1-2 V DC with the circuitry employed. Of course if any of the diodes fail for any reason, now that's a different story.... that means major kaboom, sparks and smoke.

ken chaffee 28th December 2014 01:58 PM

That's the whole problem most small package full wave rectifiers are rated 5-10 amps. Even with a 5 amp fuse one shorted diode will blow up the cap before the fuse blows. The circuit as drawn will be prone to failure with any kind of load placed on it.

dragonweed 28th December 2014 05:16 PM

Not to contradict you, but in my 40 years of service practice I've never found one single rectifier blown in amplifiers... everything else yes, but no diode bridges. Those thing are incredibly rugged, a 5A nominal current rated rectifier can take 50-80A peaks -for short time of course. So as long as their voltage rating is sufficient (at least 4-600V) -and you do not put a short circuit across them- you need not worry about their reliability

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