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We noticed you attached photosto your comment.
Have a look here to a see a hummy speaker treatment .
Those EMI filters contain Bauln ferromagnetic bucking coils that only work on AC lines to cancel common mode noise.
Except for a few small capacitors this filter is quite useless in a 12VDC car.
Better you should attend to the alternator output and also verify the ignition resistance wiring is correct for best noise reduction.
See the kind of circuitry you will find inside an AC EMI filter like your picture.
Electro Magnetic Interference does not cover RFI Radiated Frequency Interference that is found in your car.
Does the interference in your speakers still occur when your engine is OFF ??
If Yes when off look at the amplifiers as the noise source..
If No ... when running ... Try putting the amplifiers on a separate battery, just to find out if the noise is radiated ? or only conducted ?
Let us know !
I installed the DC filter as you suggested.
the amplifier works great when plugged directly into my phone. (with engine running )
but when the Bluetooth is powered up and plugged into the Amp the interference starts. its picking up the engine RPM's.
the Bluetooth receiver isn't designed for use in cars ..... ?
Good to hear :-)
Remember we covered conducted EMI which you have solved.
However there is still radiated noise RFI to contend or live with.
I assume the lap top is self powered.
yes, the laptop was just running off its battery.
You know how birds can sit on top power 2200 Volt AC wires.
Your laptop is a bird !
Maybe I could use a battery pack to power the Bluetooth receiver, I have rechargeable batteries. how much current do those receivers draw?
how to get 5 volts from 1.5 volt cells ?
would 3 AAA's be sufficient ?
Three cells start low at 4.5 volts and continue discharging down from there that Bluetooth receiver wont run very long as the voltage falls below 4.volts.
I would use 4 calls A,B or C in series with a single 1N4002 diode in series to lower the 5 Volts down to 5.5 volts DC.
Now ... you must learn how much current those Bluetooth receivers draw?
That will determine how long a pleasure of battery power can work for you.
on an other tack, I would attempt to place shield cables around your spark wire leads to minimize the RFI..
Are the speakers and radio stock or after market?
That EMI filter will not help at all. The interference is proabbly not coming through the power wires feeding the radio. If it's an after market radio than it may not have been installed and grounded correctly thus causing the interfearance.
how does one wire up a noise filter for 12 volt dc ? this item arrived with no instruction . thanks
Disconnect the plus + wire from the amplifier and twist connect it to the Blue input filter wire.
Then feed the Red output filter wire to the amplifier power plus.
Finally ground the Black negative filter wire to a strong metallic anchor point using sheet metal screw and a washer to make a very low resistance contact.
the 12 dc filter arrived, but without instructions and no English, how does one wire them up ?
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Posted:Jan 25, 2014
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