Hi Cap DR Hum Glorious Hum Problem

Like a few on here probably my hi cap DR hums, I purchased it mint used and wasn’t told it was a humdinger or maybe the chap wasn’t aware of it. Anyways the gum is a big problem for me so much so that I have gone back to the Supernait without no cap attached ( doesn’t sound as good granted but I find in concentrating on the him when the DR is insitu so it’s currently out of the system ).
I have read a few posts on here before posting myself about trying other plug sockets / dedicated mains sockets / dc blockers and the like and would like to ask please?.

  1. Can you plug the Hicap into other plug sockets without anything attached to see if the hum is present when you power it up? I’m not willing to try this until some one says it won’t damage it or don’t do that etc?.

  2. Could the Audiolab DC blocker potentially work ?, I believe Richer Sounds sell these and would possibly arrange to take the power supply into the shop to see if it works.

I rent my home so changing or adding mains supplies is not possible and would invalidate my tenancy so that isn’t an option.

Anyone have any ideas or answers I would greatly appreciate it

1 - No problem powering up the Hicap with nothing attached to it. Just give it a few minutes after powering it off before connecting it back up to your Supernait.

2 - Better to see if you can trial the DC blocker in your home to hear its effect on the Hicap on your home mains supply. I believe @DiggyGun has had good results with the blocker you suggest.

There is a useful thread here which may help you out


I have 4 Audiolab Dc Blockers in my non naim system, tried one on the Naim one (on the SN3 / HCDR the same as you) and removed it near instantly, sapped all the energy.

In the other system they work fine with various components, both amps and sources, just not in the Naim to my ears.

Didn’t bother working through all the variations to find out why, was so marked I didn’t bother.

My HCDr hums occasionally, most the time silent, guessing it coincides with other domestic appliances.

Maybe it didn’t hum with the last owner…? Ask them.

DC Blockers are generally not recommended, with Naim kit.

Do read the link posted above, by @james_n . You could learn a lot.

I think the consensus is that “conditioners” are not recommended rather than DC blockers.
There are several users of DC blockers on here who state it has no effect on SQ.
Ofcourse, like anything, it’s best to eliminate the cause of you can rather than deal with the symptoms.

I have 2 of the Audiolab blockers; one on the hicap, one on the sn2. They work for me, and don’t suck any energy from the music.

I’ve got an IFI DC Blocker on my 300DR it’s resolved the hum from the power supply, and hasn’t negatively impacted sound quality

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Thanks for the answers, just to be certain before I try plugging it into other plug sockets around the house , I won’t damage it by disconnecting the snaics and plugging it into mains sockets without it peering anything. Apologies I don’t want to damage it!.

Thanks I already read that a few weeks ago when i received the power supply. Good article it is, It looks like nothing can be done to minimise the noise. It’s not loud as such but once the music is finished and power supply is left on its noticeable and disturbs watching the tv, so off it goes. I guess it may have to admit defeat and sell it.

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Its your choice. Another one might be less noisy… :thinking:

Correct. Turn it and the SN off and wait about 30 seconds before disconnecting the Hicap. You can then plug it into another socket.

Another thing to try is to turn everything in the house off, other than the Naim. See if the hum stops. If it does, turn other things on, one at a time. That should tell you what is causing the hum. Maybe you could then put a DC blocker on that. I’m assuming that a DC blocker works both ways, but may be wrong on that, as I have no experience of them.

The principle of DC blockers is that it goes on the thing that hums,not the thing causing the hum.

If the hum is constant and unchanging, that indicates that the transformer is naturally noisy.
If the hum is variable, that’s more indicative that it’s the so called DC problem. In that case follow HungaryHalibut suggestions to try to find the item that’s the cause of the waveform distortion.

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I have a an Ifi DC blocker on my HCDR, I was getting intermittent quite loud humming at different times of the day. This pretty much resolved the issue with no degradation of sound quality.

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As mentioned above, I use two IFI DC Blockers on my NAP 250s.

Doesn’t completely stop the hum, but takes away 95% of it with absolutely no damaging effect on the SQ.

Previously you could hear the hum from the sitting position when nothing was playing. Now, you can’t and you have to put your ear right next to the 250 to hear the hum.

Job done, as they say.


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Thanks. I suspected that might be the case, hence my hesitation.


The guide mentioned earlier does give you some suggestions on things to try to identify what is, and what isn’t causing the hum, so if you have tried those, it might help us to know the results of those tests.

Another thing you could do is to plug the HiCap in a different house, different street to see if it hums identically. Also even try and temporarily plug into a different circuit in your house to see if that has any effect.

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I hate to say this but it all seems fairly random and a little frustrating in my experience. In my previous house my Hi Cap hummed loudly. It was replaced with a SuperCap which did not really hum at all. A SuperCap which I borrowed prior to that was noisier. Same circuit. Same mains lead , same block etc. My current 552 PS hummed quite loudly in that house. It still isn’t entirely quiet now but in the new environment it is significantly quieter.
I also found that in my previous address the XPS DR was considerably quieter than the 555 PS which replaced it.
I’d try the DC blocker if I were you but as I have alluded to, it seems that sometimes there is little to explain why some units hum and some don’t!
Best of luck and hope you find a solution which doesn’t compromise sound quality.


I’m going to try plugging it in different sockets tried all five in lounge both direct and via a mains extension and the results are the same - hum. Wish the hifi shops would loan me one of those ifi gadgets £120 is a lot to pay to find out it doesn’t do anything

I have tried it in all downstairs sockets , switched everything off and switched on again fridge washing machine, tv etc still present. What I have noticed when plugged into kitchen socket the hum seems to increase in volume then dissipates then increases like it’s cycling - sort of like waves going into the shore. It fades to a tolerable level them comes back this happens approx in 20 second cycles. Unless I’m imagining it!!