Does dc blocker affect SQ?

Hi all,
I had hicap DR and Nap 250 DR humming. when listening to the music this does not affect at all, I also notice it reduces a bit, but in the early morning it annoyed me a bit, therefore first I bought a ifi dc blocker that I put on the hicap, later on a second one (that is a dc locker plus) that I put on the Nap 250 dr.
Now it is deadly silent
I honestly did not notice it affected SQ or dynamics, what’s your view?
I know that generally filters are not recommended, can we do an exception for pure DC blockers?
is there anybody that takes it off when listening for long listening sessions?

The simple answer is some people have had a benefit, some haven’t. Depends on so many variables in a house. In your case, try and remove your Blockers to see what effect it has, then report back here.

You might also want to have a look at this


It is widely known and accepted that vibrations affect the performance of electronic components, not sure why the laws of physics would not apply to Naim components. Humming, which causes the whole box to vibrate, should be dealt with if optimum performance is desired.

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That you shouldn’t concern yourself what other people think - when you have done the experiment in your system, in your room and with your ears.


During the time I was experimenting with making my own DC Offset filters, I found it gives a slight improvment in SQ & thats with a power supply that was very voltage steady & quiet.
I’ve read others comment on the same small but possitive changes in SQ.


Mechanical humming transformers due to DC gets saturated. Not only do they vibrate and create microphonics, they also do not perform as well as a non saturated transformer. I believe that is why many find their system sounds better when they do an off/on cycle because then you remove the saturation. DC filtering has never made it worse in my system, only better. And silent.


Thanks all, positive impact from dc blockers from everybody, I feel better

I’m glad you feel better now Gruido71, but I only have bad experience with DC blockers. I tried several (well reviewed) DC blockers (AH DC offset killer, Supra, Audiolab, iFi), and they all had the same negative impact on the sq of my system.

One more than the other, but all DC blockers I tried made the music sound softer, lacking in sparkle and attack. Also dynamics seemed to be affected, making the music sound dull, lifeless.

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Thanks, I will try a comparison test. A solution might be to take off filters for long music sessions

Thats not my experience with the electricity supply here in rural France.
Edit: ATL blocker.

Now that’s had a moment to sink in - my experience with DC Blockers/mains conditioners has been entirely negative.

Whenever I’ve tried one (and one manufacturer asked that I run his device for a month before judging) the proof has been in the sense of relief once it’s removed.


If you don’t need one (you have good symmetrical mains supply cycles, no ‘DC offset’ at all ), then as with putting anything in the mains supply connection and increasing the apparent impedance, there is likely to be a degree of deterioratory effect on the sound. (How much deterioration is likely to be quite variable.)

However, if the mains supply has that defect (asymmetrical mains supply cycles, ‘DC offset’), then the improvement in the functioning of the transformer(s) is likely to be of greater benefit than the negative effect of the increased impedance. (How much improvement is likely to be quite variable.)


I have used two IFI DC Blockers previously on two Naim NAP 250’s which had a very loud hum, which could be heard from the listening position, when no music was playing.

Did the trick, virtually all the hum was gone, could only hear it if your ear was close up to the amp.

No noticeable detrimental effect to the SQ.



I’ll second the IFI DC Blocker…worked a treat on my humming Supercap2. I really wasn’t expecting it to have much if any effect (after an Isotek block did nothing, but cost a lot more), but it has…a bargain to me for the cost. Haven’t noticed any impact on SQ so far.


I honestly do appreciate the silence ifi dc blocker brought back when no music is playing and does not bother me when kids are playing and we are happily listening to soft music. When I am by myself and having listening session I take away dc blockers: music becomes more full and rich. With dc blockers is a bit on diet…

If you need to get rid of excessive transformer hum then a DC blocker will do that and it is a very simple device which is essentially a capacitor inserted into the live wire at the end of your power cord. The capacitor has an extremely high impedance for DC so it blocks any DC component from entering the amplifier’s transformer. You need a fairly large value capacitor to make sure that the 50-60Hz AC component doesn’t get significantly attenuated although this is not a huge issue because the voltage of your mains fluctuates anyway and a well designed power supply with good regulation can easily cope with such fluctuations.

I will say that if you can hear differences between different power cables, sockets or plugs then inserting consumer grade capacitor into the power line may not strike you as the best idea.

Well said… it’s all about the design of the DC blocker and the degree of asymmetry in your mains. If you have significant asymmetry large efficient transformers, especially toroidal transformers, will be driven into saturation (this the DC related buzzing you hear) and be producing many harmonics and distortions in the secondary windings which then get passed to rectification and regulation. Whether this added distortion and noise like RFI detracts from your musical enjoyment as Adam suggests is down to you and your ears.
Not all distortion and noise is necessarily bad when it comes to audio, and of course the side effects of a certain DC blocker design may be more objectionable than the added noise from saturated transformer windings. DifferentcDC blocker designs will work differently and may well cause their own higher frequency harmonics … although loudspeaker buzz might be largely or completely reduced.

Also, not all variable and loud hum from transformers is an indication of DC on the mains… it can also be caused by harmonics on the mains due to loading and environmental effects from your power distributor and associated sub station. Here a DC blocker will make no difference at all in removing the hum.

For information, I see that iFI have a new model, the DC Blocker +.

Differences as per the attached photo.


True, but the elephant in the room is that a severely humming transformer will spread vibrations all over the equipment and even the cables connected to it, and the resulting microphonics are never welcomed.

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This also very true… the audio effects of a buzzing heavily saturating transformer can be very distracting and unpleasant to have in your listening room.