DC blockers Design and upgrades

[andyr]

4 hours ago, Patrick. K. said:

I ordered a dc block pcb from aliexpress,  these are very common and have 3x the dc blocking capability of the audiolab dc block, for only 15 usd, and it works just as good, if not better, I cut the cable of the plug box extension cable, connected the ground through and voila, my amps and dac all on the dc blocker, It has nichicon capacitors,  (real?)... so for 20 usd you have a extension cord with multiple plugs, and 3x 0.7v of dc block...

 

And here is a pic of the internals of the mains DC blocker that I make:

 

 

 

It is 25x the cost of your AliExpress one.  It also uses Nichicon caps - but these alone cost me USD100!  And then there is a 30a diode bridge (the square thing above the caps).

 

Mine can pass the full 10a available from a wall socket; I suggest that:

1. the so-called 'Nichicon' caps in your AliExpress one may not actually be genuine - given the price you pay.  
2. and the amount of capacitance they supply is inadequate.  (The caps I use - and there are 6 of them - are Nichicon Gold Tune 2200uF/100v.)

 

[Patrick. K.]

5 hours ago, andyr said:

 

And here is a pic of the internals of the mains DC blocker that I make:

 

 

 

It is 25x the cost of your AliExpress one.  It also uses Nichicon caps - but these alone cost me USD100!  And then there is a 30a diode bridge (the square thing above the caps).

 

Mine can pass the full 10a available from a wall socket; I suggest that:

1. the so-called 'Nichicon' caps in your AliExpress one may not actually be genuine - given the price you pay.  
2. and the amount of capacitance they supply is inadequate.  (The caps I use - and there are 6 of them - are Nichicon Gold Tune 2200uF/100v.)

 

You spend 375 to 500usd on that ...???!!! I hope not, those capacitors don't cost that much I would hope. And you don't have a mkp on them? 

Ps the amount is also 2200uf per capacitor,  so 6600uf for each diode bridge.. I don't believe you would benefit from a audio grade in that location,  .. or am I missing a crucial bit of how this circuit operates maybe..

Edited July 30, 2024 by Patrick. K.

[TK77]

On 29/07/2024 at 3:59 PM, Bigflyingfish said:

First impressions of Audio Lab

DC blocker are favorable.

Hopefully more extended listening tonight.

Now that I'm operational again, and I had a quick check that everything is OK, I finally opened the Audio Lab DC blocker I bought before I ran into my issues and have just plugged it in.

 

First impressions also favourable here and definitely more extended listening for the rest of the evening.

[Patrick. K.]

5 hours ago, klm said:

The caps are indeed fake.

One of the issues with the extension board arrangement as shown is the possibility of any device plugged into that board with a switch mode power supply will generate dc into the extension board and thus into every other power supply attached to that same board and thus defeating the purpose. DC blockers should be considered gatekeepers to every component.

Those capacitors are fake why? Those are priced 1.3 euro when you buy 1 at a audio retail store, If one would buy 10.000 at once at a wholesale price do you have any idea how cheap they would become then,.. I figure about 40cents a piece...  if you do a price check on mouser for instance and see how the price drops with the purchase of 1000, or more....I don't believe these to be fake anymore after doing some research.  The price is in no way a indication they have to be 100% fake.  @andyr do you believe the circuit you use functions better, and had more capacity for blocking DC? I would want to make it and do a comparison,  I have some 22.000uf 63v capacitors on hand , and a 50A diode bridge...

[Patrick. K.]

 

 

This is the place to discuss all about DC blockers, circuits and other mains filtering/ power conditioning systems 

[muon*]

My Transport and DAC each came standard with DC Blocking internally.

Each has 2 x 82000uf capacitance for DC Blocking, but an average brand of cap so will at some point change them just for peace of mind longer term.

 

Have had this sealed DC Blocker for over 10 years, I used in a valve phono stage for a while to stop the C-Core power transformer from buzzing, only good for that or a CD Player or DAC. This particular one does It's job connected on the neutral line.

 

 

 

 

Edited July 31, 2024 by muon*

[HdB]

That's a really neat build Ian -

 

I too have found an improvement using quality components.  I recently picked up an "audiolab 'dc blocker' (very neat case) and it works very well, possibly better that the basic design, for some reason.

 

I noticed that they've now advertising a "dc blocker 6" but for $719 - what special filter are added, do you know? 

It seems a pretty extreme price if only extra mains outputs sockets.

[muon*]

29 minutes ago, HdB said:

That's a really neat build Ian -

 

I too have found an improvement using quality components.  I recently picked up an "audiolab 'dc blocker' (very neat case) and it works very well, possibly better that the basic design, for some reason.

 

I noticed that they've now advertising a "dc blocker 6" but for $719 - what special filter are added, do you know? 

It seems a pretty extreme price if only extra mains outputs sockets.

No idea what happens with the dc blocker 6, I saw it when I was googling earlier and looked at the price and closed the window

 

Edited July 31, 2024 by muon*
typo

[andyr]

1 hour ago, muon* said:

My Transport and DAC each came standard with DC Blocking internally.

Each has 2 x 82000uf capacitance for DC Blocking, but an average brand of cap so will at some point change them just for peace of mind longer term.

 

Surely the DC blocking circuit in your Transport and DAC must contain more than just a couple of large caps, Ian?

 

Here's Rod Elliott's DC block schematic:

 

 

 

 

 

[muon*]

1 hour ago, andyr said:

 

Surely the DC blocking circuit in your Transport and DAC must contain more than just a couple of large caps, Ian?

 

Here's Rod Elliott's DC block schematic:

 

 

 

 

 

Example of one.

The bridge rec used is RBV5006.

The two caps for the one in the DAC are 82000uf each, the two in the one in the transport are 100000uf each.

Edited July 31, 2024 by muon*

[HdB]

I went a bit 'nuts' and added one of those  Shurter power line filters and a Siemens dual choke (for the active and neutral lines) with another filter cap - can't remember where the circuit came from but pretty standard i think

Anyway, for all the fancy gizmos and things, it didn't seem to make any different to the basic version - I was a bit p'd off as went to quite a bit of trouble - maybe these days with so much more rf in the air and wifi everything, it might be worth trying again

 

Curiously, on a slightly different subect that might be interesting, I started using those fancy fet type bridges based on the LT4320 chip instead of diodes/bridges - seems to produce much quieter power - the low rds fets are getting a bit harder to find now but more smd versions.

 

Pardon the divergence! 

[Patrick. K.]

I am trying to find out what the best circuit is , I see many different ones, using 1 to 3 diode bridges with capacitors as small as 4700uf x2 up to 4 X 68000, I did some AB testing between the audiolab and the pcb I got from aliexpress,  and they seem exactly the same, There is a very clear improvement (in my system) in upper mid and high detail, same like when you dropped the noise floor of a piece of gear significantly... I am now looking to experiment with a schematic that uses only one 50A1000v bridge and 2 large 68000 uf capacitors , I have some capacitors from a diy solid state power supply,  My toroidy power transformers still buzz very faintly so I wonder if upping the capacitance will change that. Also the other question is about ESR, I read it is important to have low esr as possible and high leakage current, so the use of many small capacitors would be preferable.  There is much to find on this topic but I guess the best way to really find out is trial,  Nice gear @muon*, no longer the GD?

Edited July 31, 2024 by Patrick. K.

[HdB]

The dc trap will by it's very nature block any dc component carried in on your mains supply.  Unless you have some really bad power consuption devices on your mains, the dc component should be less than 1v dc, hence 1 single bridge is sufficient - if you need multiple diodes, you have a significant power supply quality problem ...

 

It's never a bad idea to use good quality caps/diodes anywhere near power filters despite the extra cost - I gave up buying electro caps from China a long time ago as there is always a question about quality (voltage/current/esr/age/etc) - I'd suggest paying the higher price for known quality caps.

 

Multiple caps in parallel generally don't share the current load evenly so there's the risk of early failure. 

 

It might sound a bit overkill but you could try another trap on the neutral wire and see if it reduces transformer misbehaviour - a simple thing to try.

 

There might be other added 'weavils' on your supply creating problems so maybe you need to expand your 'clean power quest' to include extra line filters, balanced power, earth/ground problems, etc - power supply 'bugs' are rarely simple these days 

 

 

[andyr]

5 hours ago, HdB said:

It's never a bad idea to use good quality caps/diodes anywhere near power filters despite the extra cost - I gave up buying electro caps from China a long time ago as there is always a question about quality (voltage/current/esr/age/etc) - I'd suggest paying the higher price for known quality caps.

 

  Absoloootely!

 

5 hours ago, HdB said:

Multiple caps in parallel generally don't share the current load evenly so there's the risk of early failure. 

 

But (assuming the use of 'quality' caps in both cases) multiple caps give a lower ESR than a single cap of the same value.  I would've thought this is a good thing?

 

[HdB]

I was a bit curious about that myself awhile back Andy so I paralleled up  3 x 2,200uF caps to see if there was any difference between these and a single 4,700uF and 10,000uf one (pairs as per network, naturally) and found no difference, or noticeable difference to be more precise - tried Siemens, Epcos, Rifa, Nichicons, Slit Foils, and a few others that I use in power supplies. 

That wasn't exhaustive or particularly methodical but gives an indication - I sourced the very same components as in the "audiolab dc blocker" box and obtained the same performance - a rather wierd arrangement but works quite well

 

found some old Siemens screw cap 4,700/50v (at Rockby, local electronics store), reformed and they work 'just fine' on dc traps - not so good as power supply filters unfortunately

 

Far to much "grunge' on our mains these days ...

[Glass_and_Tubes]

@Patrick. K. do you have photo or link to the original Aliexpress you unit you bought? Would love to see what those loolk like especially for less technical folks not handy at building. thanks!

[Patrick. K.]

14 hours ago, Glass_and_Tubes said:

@Patrick. K. do you have photo or link to the original Aliexpress you unit you bought? Would love to see what those loolk like especially for less technical folks not handy at building. thanks!

Here you go

[HdB]

There's a lot of 16v caps - can't see the value or manufacturer - 3 diode arrays indicates expected very high dc offset values that wouldn't be 'fixed' by the simple dc trap - you could dump 2 of them as parallel bridges/diodes don't share current much better than capacitors -  Is that blue device a "soft-start" thermistor?

 

At that price, it's worth a try - it does need a decent 'safe' case with input/output plugs/sockets so a bit more work involved. 

[Patrick. K.]

That blue thing is a varistor,  the caps are 9 X 2200uf with nichicon label, I assume they use 3 bridges to have 3x 1.4v drop..

[HdB]

Have you tried it out with a reasonable load?

[HdB]

Nobody is going to be able to use or maintain a power supply that has 5v dc component so 3 bridges are just there for show, unless they combine them for that neblous 25A rating.   Not that it matters much as the "proof is in the application", or not ...

[Patrick. K.]

I have 2 300va toroidal transformers of my kt150 class AB monoblocks on it and a 60va ares2 denafrips dac, I don't know what the max load would be when I play at rock concerts SPL, but hope this answers your question in some way

[andyr]

5 hours ago, Patrick. K. said:

I have 2 300va toroidal transformers of my kt150 class AB monoblocks on it and a 60va ares2 denafrips dac, I don't know what the max load would be when I play at rock concerts SPL, but hope this answers your question in some way

 

2x KT150s per channel in a PP arrangement (for Class AB) ==> typically, 100w per channel.

 

Say (worse case scenario) amp is 25% efficient ==> 800w sucked from the wall, at max power.

 

Say you are running at half this, playing at 'rock concert levels' ==> 400w from the wall socket.

 

Plus an extra 60 for the Ares2.

 

Say, 500w from the wall.

 

So, at 230v mains ... you are drawing 2.2 amps.

 

[HdB]

Yeah Andy,  pretty normal & light load with no tricky or troublesome switchers

 

So, maybe 10-15A at startup peak current (without a 'soft-start' circuit) -

Not sure about the amount of 'hum' in the transformer with the dc filter 'trap' inserted but if the supply has substantial peak chopping, ground offset, etc, it's possible I guess 

 

Some years ago, a similar problem to this required changing to a balanced mains transformer - not a simple exercise for domestic systems.

 

 

[Addicted to music]

On 01/08/2024 at 2:37 AM, Patrick. K. said:

,  My toroidy power transformers still buzz very faintly so I wonder if upping the capacitance will change that. Also the other question is about ESR, I read it is important to have low esr as possible and high leakage current, so the use of many small capacitors would be preferable.  There is much to find on this topic but I guess the best way t

 

ESR in power supply is extremely important, as this goes high due to age, usage and environmental exposure,  it increases loading on the transformer hence the buzzing.      Another issue that causes buzzing through the speaker and increased mechanical vibrations with the transformer