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Fixing Noise?

Joe Elton

Apr 24, 2015
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I have built a Bluetooth Stereo System but i'm getting really bad static noise in it. I'm using a 5V USB DC step-down converter from a 12V 4 Amp DC PSU(the model is YU1208). When i use the Bluetooth receiver it puts out lots of noise (literally through the speakers) but when it hooked up to a 12V battery instead of the YU1208, the Bluetooth receiver works perfectly. i tried a choke and a 680μF capacitor in series with the USB module but it still is getting the noise. What is the cause of this noise and Is their any easy solutions to fix it or will i have to find a new 12V power supply?
 

HellasTechn

Apr 14, 2013
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I'm using a 5V USB DC step-down converter from a 12V 4 Amp DC PSU(the model is YU1208).
Do you mean a 5v regulator ?

When i use the Bluetooth receiver it puts out lots of noise (literally through the speakers) but when it hooked up to a 12V battery instead of the YU1208, the Bluetooth receiver works perfectly.

If it can run on 12Volts then why do you reduce it to 5 volts ?

i tried a choke and a 680μF capacitor in series with the USB module but it still is getting the noise.

You could try to connect it in paralel with the usb nodule's output. i would also recomend to try useing an other capacitor in paralel with the 12v psu output (say a 2200mf 25volt)

What is the cause of this noise and Is their any easy solutions to fix it or will i have to find a new 12V power supply?

This is a switching PSU. switching psu are not the best choice for devices vulnerable to noise. The Battery provides you with a steady and nice 12v output. maybe that is why you get noise.
 
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HellasTechn

Apr 14, 2013
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Ok now i figured it out . Maybe you mean that you hooked the step-down converter to the 12Volt battery.

In that case then i think you may consider useing a linear 12V supply or straight a linear 5Volt supply without the need to use a DC to DC stepdown circuit.
 

Joe Elton

Apr 24, 2015
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sorry for the confusion and thanks for the reply, a linear power supply looks like the way to go, i just had a look at some graph of the difference between the noise of the two. Now just to find the right one, for the right price.
 

HellasTechn

Apr 14, 2013
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how many amps do you need to pull from your power supply ?

A 220 or 110 volt to 5 Volt transformer 3-4 Amps would not cost more than 10 euro here. i bet that price should be same over there.

A bridge rectifier and a smoothing capacitor cost like 2-3 euro tops.

On the other hand a ready to use 220 or 110 volt to 5 volt 3-4 Amps transformer psu would not cost more than 15 euro.
 

HellasTechn

Apr 14, 2013
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just had a look at some graph of the difference between the noise of the two. Now just to find the right one, for the right price.

Did you use oscilloscope for that ?

before you buy a new psu try the fix with the capacitors i recommended before. it might work.
 

Rleo6965

Jan 22, 2012
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Probably smps power supply have sense overcurrent causing to vary its dc output and becomes static noise.
 
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