Ifi DC Blocker

I eventually got sick of feeling like I was living in a bedsit, with a fridge freezer in the room.
After jumping through all the hoops to get rid of the problem, I bought one of these on a whim.
Plugged it in. Job done.


All good stuff, and indeed saturating transformers can be really irritating as well as produce pollution on your home mains, out of interest does the manufacturer state what inductive surge current the device is specified to. This is rather important in my opinion as switching on a highly inductive load, like a large toroidal transformer which is probably what was causing the hum, will typically cause a surge current across the capacitor protection diodes causing them to heat briefly. If that surge current is greater than specified over time the protection diodes will likely fail, which could then cause the electrolytic capacitors to explode/fail on turn on within the DC blocker.
I ask as the device looks quite small, and I suspect you are connecting to a large power amp?

‘morning Simon, I’ve wondered the same question.
My own design DC filter has 45amp diodes specifically to cover that eventuality.
I’ve noted a few circuit diagrams on www recently with the diodes bypassed with a resistor, no purpose that I can see other than diode relief.

However, iFi are more into smart electronics so I suspect these little boxes might be full of chips & IC’s rather than series capacitors. One thing for sure is just one of my 10,000uF caps won’t fit inside, let alone the four of them.

Re your question on surge current, they are
Maximum rating >7A, continuous current rating 4A

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I have some little noise on speakers, depending on the moment on the day. Sometimes it’s quite silent, sometimes it’s like a mechanical humming or pop pops, heard only if my ear is very near the speaker ( around 1 cm).
Can the Ifi dc blocker remove that ?

hi FR, I doubt it, a DC Offset filter is intended to reduce transformer noise.
If your units transformers have noise variations that match the noise variations from the speakers, then it might be possible.

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I agree with @Mike-B it sounds more like the effects of induced RFI you are hearing


IFI also do a Ground Defender which is to remove ground loops

Get one that does free returns and try it. If it works, job done, if not return and nothing lost.


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curious want it actually does. Ground loops ar in fact induction loops - and background magnetic field in your house, typically 50 Hz in Europe, is induced into the loop - and if that loop is associated with a signal ground you can hear a hum - depending on the voltage induced.
One way is to remove is to make the loop lossy so the induced voltage is too low to be problematic… you could use a series capacitor of an appropriate value but the might lessen deep bass performance, or even use a steep notch filter based on the induced frequency - albeit might affect bass performance a little.

I must admit I am immediately suspicious with the term ‘AI’ applied to a device like this… what is the intelligence - does this mean an algorithm or basic logic - I don’t think ground loops are caused by a lack of intelligence…


‘AI’ has become the new ‘Smart’ which took over from ‘digital’ which took over ‘electronic or e’ which tools over from ‘brain’ or ‘electronic brain’ - right back to the Victorian/Edwardian era where we used ‘wonder’ or ‘magical’

I do apologise for being cynical… I guess if it really is innovative - it will have almost certainly have a patent registration and then we could see at a higher level what it is actually doing.

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@Simon-in-Suffolk I’ve seen a few people on here using them, so on the basis of being able to return it if I wasn’t happy, I decided to give one a go.
I was a little dubious about the little fella’s capacity for current, so wouldn’t want to put it in the main line to the power block/strip which supplies all the boxes.

This one is currently plugged directly into the back of the SupercapDR, as that’s the noisiest box this week.
Once I’ve done a few back to back listens, to make sure that I’m not hearing anything detrimental, I’ll likely get another two.
Specs from the packaging below.

@frenchrooster as far as I know, noises such as yours from the speakers are more likely to be ground loops. You can introduce these yourself by incorrect grounding of the equipment.
I found a diagram showing the best way to do it whilst trying to sort out my DC problems.
Image courtesy of RF Router who make the box in the picture.


Thanks Mike. So I will try to observe if there is also more noise from the Ear amp unit when there’s more noise in the speakers.
I had the same phenomenon with my ex NC 250, but it was more audible.

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How can I reduce RFI then , Simon ?

The question is now : do I have ground loop problems or RFI?
As the noise is not permanent, I suspect then RFI more.

If these noises are ground loops, shouldn’t they be permanent ? Depending on the moments of the day, they can be heard or quite not in my case.

You could try an iFI GND Defender to see if it works. If not, send it back.

No harm in trying and at least it would rule out a ground loop hum.



Really not my field of expertise.
I use the AV bypass function most evenings. I have an AV receiver connected to the 252.
The receiver used to be connected to a SN3 and it made terrible noises if you didn’t use the ground post on the back.

When the 252 arrived I continued to ground both devices.
It wasn’t until I saw the diagram which I posted above, that I realised I was probably causing a ground loop with the way that it was grounded previously.
I don’t have the RF Router. Just grounding the devices properly works for me.

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FR, probably not easily to be honest. I suspect it’s via your speaker cable so you could always try repositioning it. Also do you have any home network equipment nearby, or Ethernet leads. If so can you move them away from your hifi?

I positioned recently differently my speakers cables . They are away of all cables.
How about these ?

12 Pcs Magnetic Ferrite Cores EMI RFI Noise Filter Clip for 13mm Diameter-Black

Ferrite on speaker cables will not do much, most of the general purpose ferrite mix formula only become effective around and above 100 MHz.
Even the lowest frequency formula is not very effective below 1 MHz
But OK they won’t do much, but they won’t do any harm either.


Indeed, but no harm in trying. Put the ferrite chokes near the amp.


AI ground detection?? :rofl:

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