Shutting down my system often and Hum

This Spring and Summer, I’ve shut off my system more often than ever before because of the frequent storms in my part of the U.S. I’ve probably averaged 1 or 2 times per week almost every week – thunder storms, heavy rain, power outages… Each time, I turn off everything (I know I should unplug my gear but that’s a lot of trouble and I’ve been fine just turning the system off). Funny thing is that my system seems to sound better than ever since turning it on and off so frequently. Also, it doesn’t seem to need as much time anymore to get back to sounding optimal after turn off.

Another strange thing…I’ve always noticed that my power supplies (555PS, SCaps, 300DR) hum at certain times of the day–usually late at night strangely. A few weeks ago, the lawn maintenance service hit the large power box in front of my home–it feeds several homes, so the power had to be turned off and the power utility had to supply portable power to the homes until the issue was resolved. (I powered down my system the whole time.) The power utility ended up replacing the large power box outside with a new and larger one with all new connections. Now – no more hum! I wonder if the power utilities are introducing DC into the line and that is what causes the hum problems common in Naim power supplies.

Has anybody else had these experiences?

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Interresting… I also have a supercap dr with a hum. It is always there. I experience no hume at the 250dr. The ScDr has the age to have a service next year or so. Could that fix the problem?
Otherwise, if the main power causes the hume, can it be fixed with a noise killer e.g. Isotek or Furutech?
As far as I know, filters do no good for Naim gear in general.


Yes this is one of the possible causes.

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I very much doubt a change in whatever that box might be would introduce so called DC offset, I’m guessing the box is a transformer and the increased hum might be caused by a higher voltage. e.g. it was 110v & now it’s 120v
My supply was adjusted down a few months ago & the hum level is now not so noticeable.
It might be worth contacting your utility and asking them to check it.

He has no hum anymore after the change :slight_smile:

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Regarding system shutdown. I’ve had the same experience with my system that has been shutdown a few times and rebuilt twice this summer due to building work and holidays etc. I haven’t noticed the big performance deficite on initial switch that I was expecting. When I first acquired my 52 it seemed to take weeks to settle down, but now it seemed to be relatively unaffected by these recent shutdowns, one of which was a lengthy 2+ months.

Unless you’ve unplugged it you are wasting your time. 50000+ volts of lightning isn’t going to stopped by a push-button switch on a Naim amp in the off position :thinking:

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Confuzzed dot com …… sorry, it’s an age thing.
…. a friend in Minneapolis has just had his local transformer changed and his refrigerators became very noisy. Was emailing him on it only last Sunday.


Don’t look a gift horse in the mouth

This. Turning it off won’t protect anything.

If you want to leave it plugged in, talk to a local electrician about fitting a lightning protector to your supply. They are basically a fast acting ground switch device that will take lightning to ground while blowing a link to protect your power supply.

It’s a rare thing on the forum for these things to get better on their own, so is easy to become confused :slight_smile:

Don’t know for sure but I suspect not. The only Naim box I’ve had which hummed significantly was an XPS. When the DR upgrades came out I had that done + service and it hummed just as much when I got it back.


I actually have a voltage monitor on my line so that I know exactly what the voltage is coming into the house and through certain circuits at all times. I have experienced hum with various Naim components over the years and it occurs when one of two things happens, the line voltage dips to “brown out” voltage (here that would be below 110volts) or the voltage is too high (exceeding 125 volts). In the area where I am now, the voltage seldom, if ever, drops below 120volts and never exceeds 123 volts. No hum from any components anymore but the local provider also upgraded all transformers and electrical infrastructure in my immediate area to be able to provide consistent, clean 200 A service to the households (necessary if one is going to install a quick charger for a hybrid or electric vehicle). Hum was particularly bad due to near brown out voltages or excessive voltage (mainly due to the loading of the electrical grid) when I was out in the Prairies and in more rural areas here, voltage swings from 105volts to 130 volts on the Prairies was/is common and many people had whole house power line conditioners and stabilizers installed to attempt to combat these voltage swings. I do suspect that the voltage swings are the most likely source of hum induced into Naim equipment, especially if it occurs at a semi-regular time and season, the swings being highly dependent on the load on the local (or regional) power grid and infrastructure at any particular time.

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I’ve read that quite a few forum members have used DC blockers to resolve a hum problem. In my case, the hum was never so bothersome that I felt I needed a hum blocker.

That depends on whether the hum is caused by DC. There are other possible causes (see the “Starting Guide to Naim Hum/Buzz” thread I posted earlier) And it seems that in a given DC situation, some DC blockers work and some don’t:

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Yes - good advice. Going forward, I think I will unplug the whole system if bad thunder/lightening is anticipated.

DC on the grid for sure. Glad it got solved. Otherwise a DC blocker will solve that. It seems like a gamble if you get a Naim product that is more prone to humming. XPS seems to be more sensitive than other products in Naim range for some reason.

Since my hum issue seems to have been resolved thanks to landscape contractor carelessness, I think this is probably a “first” for a solution to the infamous Naim hum issue. I think I should consider myself lucky and hope that this fix (replacement of the outside power box by the utility company) remains.


I’ll be watching the news for an inexplicable surge in accidents involving cars and power boxes

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