Intermittent, pulsating buzz from my 250 DR

Last night I noticed a pulsating buzzing noise coming from what sounds like the front right of my 250 DR. I checked all of the connections and everything seemed OK. However, I noticed that the cable that goes from the back of the 250 DR to the Supercap was touching my speaker cable. I lifted it up and after a couple of seconds the buzzing stopped. I decided to call it a night and finally commit to dressing the cables correctly today.

I spent an hour or so today tidying up the cable, making sure none touched and everything was off the floor. Then an hour or so later the buzzing returned. After a couple of minutes it disappeared. Then this evening it’s comeback again. Again a few minutes later it’s gone.

My system is powered off a separate consumer unit, with three radial circuits each powering an unswitched MK Logic double socket.

Any ideas?

Thanks,
Andy

I think you are hearing is general mains contamination affecting the transformer (= infrequent buzzing) which is located on the RHS (from front). A not uncommon thing with Naim and it comes and goes.

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So, it’s a mechanical buzz coming from the front of the 250? The transformer is on the right hand side of the 250, as is the on/off switch (front right). If you disconnect the amp from the system, put it on a table and plug it in for several hours, does the buzzing occur?

It could be DC Offset.

Both my 250s have a mechanical hum, obe worse than the other.

I use an IFI DC Blocker on both which has helped to reduce it considerably.

DG…

I get something similar - a pulsating buzz is exactly how I would describe it. It’s almost always at night. It starts around 7 or so, and is usually gone by morning. If I’m doing some low level late night listening, it’s loud enough to be intrusive, and I’ll sometimes stack a couple of sofa cushions in front of the amp, which takes the edge off.

I’ve always assumed it’s caused by mains contamination of some kind. If it was a setup issue, it would be happening all the time, and I’m not aware of any electrical appliance in our house that kicks in only in the evenings.

Perfectly “normal”.

It’s not your Naim, it’s your electrical wiring. It was so bad for ma at one point, only a house move cured the hum.

Does sound like DC Offset, the problem is finding out what is causing it. It could well be from another building, in which case there is nothing you can do about it other than try out various DC Offset blockers, but they can reduce SQ.

First you should probably try to eliminate the items in your house, but turning off various circuits and seeing if the buzzing stops. If you’re brave, you could even turn off your whole House CU, but make sure you shut down any computers first

Many thanks for all of the thoughts on this. Sounds like noisy mains seems to be the overwhelming view. It’s frustrating if this is being caused by something else within our house. I had our mains feed split at the meter with a Henley block and have a separate Consumer Unit just for the Hi-Fi I thought the benefit of a separate main for the Hi-Fi was to eliminate noise from other appliances in the home.

Thanks again to everyone who responded, your thoughts and experience are always appreciated!

Andy

Andy – IME, and I have ditto wiring set-up, it will be your incoming mains which is contaminated/is experiencing either DC and/or variable voltage.

Ok thanks for clarifying HL. I’ll see how things go over the next few weeks and if it gets worse I’ll look into some sort of DC filter.

Buy one from a place that does free returns, then you’ve nothing to lose.

Alternately, see if your local dealer has one that they can loan you.

DG…

Overvoltage of your mains supply is another potential cause…

Items with a heating element can be notorious for causing this as they cycle on and off; hairdryers, electric fires, electric blankets etc…

Sadly this is much over stated, in a very large system with a big substation like a general hospital it can help, we do implement this technique on a large scale to minimise noise from big equipment affecting delicate medical kit located in another department, but we never suggest that it is noise free or goodness forbid ‘clean’, however in a home everything is electrically close coupled.

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