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Main => Audio/Jukebox/MP3 Forum => Topic started by: tteettuk on April 12, 2009, 06:37:38 am

Title: fan noise on speakers ?
Post by: tteettuk on April 12, 2009, 06:37:38 am

My power supply/fan is giving a buzz sound out of my speakers i built into my wall mounted jukebox ? how can i stop the buzz ? thanks

Title: Re: fan noise on speakers ?
Post by: BobA on April 12, 2009, 02:07:56 pm

Check out this thread on speaker hum.

http://forum.arcadecontrols.com/index.php?topic=89559.0 (http://forum.arcadecontrols.com/index.php?topic=89559.0)

Title: Re: fan noise on speakers ?
Post by: tteettuk on April 13, 2009, 03:40:17 am

Hi found its coming from a fan thats next to the small audio amp, there is nowhere i can move the amp, the fan was just a cheap 80mm led fan from ebay ?

Title: Re: fan noise on speakers ?
Post by: richms on April 13, 2009, 03:54:29 am

To be expected, they are switching coils with a pretty nasty square wave to get them to spin, and that will couple to things nearby.

Can you try re-orienting the amp board another way, or otherwise you may be able to get some screening between the 2 of them. That will only help with electic field coupling and I have a feeling that it will be more magnetic with a fan motor.

Title: Re: fan noise on speakers ?
Post by: BobA on April 13, 2009, 07:47:13 am

If you try metal screening between the two make sure it is grounded to the chassis ground so that it can be as effective as possible.  You could also cut the leds out of the fan circuit so it draws as little power as possible.    A resistive speed control will also reduce the amount of emf the fan is radiating.

Title: Re: fan noise on speakers ?
Post by: tteettuk on April 13, 2009, 06:41:13 pm

Hi i turned down the amp a little and turned up the volume on the pc and its reduced the noise a bit, I then  put a dvd in the dvd drive and it was like a motorbike going by ! Are all amp the same picking up motor noise etc ? can you get a sound card with a small amp built in, nothing to big just to drive two 5 inch car speakers ?

Title: Re: fan noise on speakers ?
Post by: tteettuk on April 14, 2009, 06:07:10 am

Hi all,
I worked out that its the lead from the pc audio output to the amp input is the problem, I disconnected the phono to phono lead from the amp and the sound went away, I unplugged the lead from the pc and it was still there, it was not untill I disconected the lead from the amp so it must be the phono to phono lead from the pc to amp, I tried a better quality one and it did not really improve, would one of the ground loop filter be any use ? as these on eBay ?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&Item=250392418513&Category=1498&_trkparms=algo%3DLVI%26its%3DI%26otn%3D1 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&Item=250392418513&Category=1498&_trkparms=algo%3DLVI%26its%3DI%26otn%3D1) many thanks

Title: Re: fan noise on speakers ?
Post by: richms on April 16, 2009, 07:54:42 am

Too hard to say.

Designing analog interconnects between things is a bit of a black art - in the real world you would have many trials to get the noise levels down.

Seems strange that a cable not connected to the PC would get noise however. I think you must have something else going on there. Post some pictures.

Title: Re: fan noise on speakers ?
Post by: tteettuk on April 28, 2009, 12:07:05 pm

Hi thanks I ran the audio amp from a brick power supply instead of a atx power supply and all is well ! thanks