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whee 26th June 2004 07:45 PM

Noise when people turn off lights
I'm just finished my amplifier, but i have one problem. Every time someone in my my building, or in my own apartment, turn off their lights, i hear a "click" in my speakers....
I don't understand it. The powersupply is "made by the book", and the ampilfier is earthed. I even tried to connect a AC filter.

Can someone help me??

lucpes 26th June 2004 08:19 PM

Try using a 250V MOV (Metal Oxide Varistor) paralleled to your mains.

AndersP 28th June 2004 07:59 AM

I had the same problem when I lived in Norway. I tried with a simple net filter for PC,s but did not succeed. When I moved home to Sweden after 9 years the problem was gone.

I know that the power system in Norway is pretty unique and that net filters have to be designed especially for norwegian conditions.

I would recommend you to contact someone at Electrocompaniet or Dynamic Precision and ask them.

hjelm 28th June 2004 09:05 AM

What more exactly is the uniqueness of the nowegian power system.
Just curious.

ashok 28th June 2004 09:05 AM

There are two ways the 'switch' noise could get into your amp.
One is through the transformer --- also try inverting the polarity of the mains cable.
The other is due to RF sensitivity. Some amps are sensitive and some are not. Of the several amps and preamps I have built , some have this problem and others don't. All in the same room.
It has baffled me and I can only think of the two reasons given above.
Does anyone else have an explanation.
Poor household wiring also has a part to play. If the return path of the wiring is not done well it is possible to 'lift' the neutral terminal by several volts when switching something else. I've seen this happen at some locations.

Graham Maynard 4th July 2004 07:36 PM

Hi whee.

Are your loudspeaker cables picking up stray voltage fields ?

Use a portable AM receiver tuned between 150kHz and 1MHz, but not to a radio station, to check for power cable routes, then make sure that your audio cables are nowhere near them.

You could try a second Zobel network across the output terminals, say 2.2 ohms and 22nF in series.

You could also try looping both output and LS return cables together two or three times through a ferrite ring.

Cheers ................ Graham.

millwood 4th July 2004 07:52 PM


Originally posted by Graham Maynard
Cheers ................ Graham.

Hi, Graham: welcome back. I don't want to lose you for good for the 3rd time.

anything to report on your first cycle distortion?

classd4sure 5th July 2004 05:45 AM

This happened to my old amplifier before, got worse and worse with time. Not so much just for lights though but appliances turning on like the fridge would make a loud pop on the speakers. This sometimes occurs even on my computer speakers!! So it's not just the amp that was dying. I had posted about this to a repair forum and they told me to replace all my transistors saying the isolation barrier was degrading and this was a very common thing with time. I didn't bother doing as they said. I was at first convinced it was the Y caps so I tried disconnecting them and it didn't help. That amp is a pile of parts now..

One thing I discovered after it was too late was a few cracked solder joints on the reservoir caps. I was told this these cracked solder joints could act as a sort of rectifier, which made sense, but these line surges shouldnt' be making it that far anyway? Doesn't hurt to make sure all your solder joints are top notch anyway.

Hope you have better luck than I did.


Graham Maynard 5th July 2004 07:53 PM

Hi Millwood,

Its already been appearing in print in Electronics World. Submitted text is way past 20,000 words already. If you get the chance to read it you'll realise why it is more than I can put in this little window.

Cheers ....... Graham.

whee 5th December 2004 06:34 PM


Originally posted by lucpes
Try using a 250V MOV (Metal Oxide Varistor) paralleled to your mains.
Witch of these is best?

Thanks to all for answers:):)

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