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Old 12th January 2015, 02:47 PM   #1
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Default LED Downlighters cause hummmmmm

I have 6 mains (240v) downlighters in my kitchen controlled by one wall switch. When they are on I get a earthloop type hum when using my phonostage. Lights off, no hum.

I assume that there is a SMPS inside each LED lamp which is causing the hum. Any ideas (other than a dark kitchen) to suppress the hum?

TiA
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Old 12th January 2015, 03:21 PM   #2
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Candles.
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Old 12th January 2015, 03:47 PM   #3
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Candles.
To see by, or to cook the meal over?
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Old 12th January 2015, 06:45 PM   #4
sesebe is offline sesebe  Romania
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You need to see exactly from were the hum it is coming.

It is radiated or it is conducted?

To reduce (to check this hypothesis) the radiations you can put a metallic box over light source, but I do not know how big there are. If you have many, disconnect all except one and the last one cover with some metal (grounded). If the problems are radiations, it is not so easy to solve

If are conducted hum, you need to put a filter on the lines of the light source.

Usually there are a combinations of this two cases.

best regard,
Bogdan
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Old 12th January 2015, 07:17 PM   #5
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Thanks Bogdan, I'll see what I can manage shielding the lights and see what happens.

If it isn't radiated, what filter would I need to put on the power cable?
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Old 12th January 2015, 07:52 PM   #6
nezbleu is offline nezbleu  Canada
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Anyone named Onion should stay out of the kitchen!
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Old 12th January 2015, 09:12 PM   #7
andyr is offline andyr  Australia
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Quote:
Originally Posted by Mr Onion View Post
I have 6 mains (240v) downlighters in my kitchen controlled by one wall switch. When they are on I get a earthloop type hum when using my phonostage. Lights off, no hum.

I assume that there is a SMPS inside each LED lamp which is causing the hum. Any ideas (other than a dark kitchen) to suppress the hum?

TiA
Other people have reported that LED lighting negatively affects their sound system. (As I am in the process of building a new house and new housing has to use LED lighting - I am not looking forward to hearing the result! Greenies have a lot to answer for, IMO! )

I think you are correct - it is the SMPS inside each LED light which is causing the problem. However, I suggest it is not radiated hash - but hash introduced into the mains wiring ... and your phono stage is most susceptible because of its high gain.

So my suggestion is to put a hash-filter between your phono stage and the wall-socket. Experiments I have done recently here in Oz have shown that Shaffner 2090-1 (1a) do a great job of stopping hash:
a) getting out of components - such as CDPs - which generally have SMPSUs, and
b) getting into components such as phono stages.


Regards,

Andy
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Old 13th January 2015, 09:18 AM   #8
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Thanks Andy, I'll check them out
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Old 13th January 2015, 09:44 AM   #9
AndrewT is offline AndrewT  Scotland
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Lighting in the UK ALWAYS runs off it's own circuit.

You can insert an effective filter at the distribution board to attenuate (cable fed) interference fed back from any and all lights in the house.
It is always better to suppress interference at source, but for tens, or approaching hundreds, of lights suppressing at the distribution board may be the only economic solution.

THEN add proper and effective RF attenuation at the audio equipment.

I recommend you ensure and RF attenuation filter be fitted to the input of EVERY bit of audio gear you build, not just to Power Amplifiers.
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Old 13th January 2015, 10:25 AM   #10
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Yes, the lights are running off of their own 5a MCB, which is physically next to the HiFi's 30a MCB in the Distribution Board (the HiFi is on its own ring circuit)

Having typed this I have just had a thought. When we had the loft re insulated, its possible that the HiFi cable was moved which would put it across the top of one or more of the LED downlighters. Before I do anything else I think I'll have to struggle up in the loft and have a look. It might be as simple as the close proximity of the two is causing the problem.

I;ll report back once I have investigated more.

Last edited by Mr Onion; 13th January 2015 at 10:27 AM.
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