Noisy MP3 Module

[dacflyer]

i bought me a MP3 Module to install into a old Boom Box (update it )
the unit works but i can hear electronic interference. the cables that came with it are sharing a common ground.
the outputs gnd and the power gnd are common to my Boom Box.
the unit runs off of 12v typical.
any suggestions on how to make the interference stop ?

[Janitor Tzap]

Hmmm................

Some how your picking up the Digital to Analog Converter of the MP3 player.

Try shielding the wires from it, or shield the whole MP3 player with a bit of tin foil.

Or even try shielding the first stage of the Amplifier circuit in the Boom Box.

A lot of car stereo's that have the plugin's for MP3 players have had this issue.
By simply placing the MP3 Player in a different position, would make it go away, or make it worse.


Signed: Janitor Tzap

[dacflyer]

it seems that the noise is backfeeding thru the power input.
i disconnected the input to the amp. and the noise was still there.. and there is really no way to shield the Mp3 player or the amp. i tried to apply isolated power via a battery. and the noise was reduced a lot.
so i think i may have to build a isolated power supply.. oh, i did put a ferrite bead on the power side, and that seemed to help some, but i think a isolated power supply is in order.
i'll goto the flea market and see what SMP i can find.. 12v SMP wall wart or such. i have plenty of the old wall wart transformers, but i think a SSL will be a better choice.

any other ideas ?

[Janitor Tzap]

Here's something on using an Isolation Transformer between a Computer Sound Card and Radio.
http://www.qsl.net/zs2pe/VHF/PROJECTS/S ... ndcard.htm

But other than making up a RC Filter circuit.
Yeah, a isolated power supply will really help.

Signed: Janitor Tzap

[dacflyer]

i went to the flea market and found me a 12V SMP wall wart.
radio is very quiet now, but if i have no input and turn the amp up all the way, you can hear the noise a little still... and if i have the radio on, and a weak station, you hear it more.
i never though them things emitted so much noise.. but either way it is ok now,, down side is, i can't use the mp3 player with batteries, but i'll most likely never use it with batteries anyway..

[Janitor Tzap]

Cool.

Here's a little experiment you can try.

Take a radio; turn it on; put it on AM; tune it so it isn't on a station.

Grab you pocket calculator; turn it on; bring it close to the Radio.

Now start crunching some number on it.
As you do, you can here the sound of the RF signals of the calculators processor being picked up by the radio.


Signed: Janitor Tzap

[dacflyer]

ya,, have done that before also...my cell phone injects noise into my computer speakers if it is sitting too near it. took me a while to realize what was causing it.. then i'd hear the noise just before it rang.

[haklesup]

Sounds like a similar issue with ground looping one often gets connecting an amplifier to a car radio connected to the same 12V source (buzzing when the car runs due to ground noise). In those cases the isolation transformer has always worked to break the ground loop

[dacflyer]

ya, no other way to isolate it..
i even tried it totally isolated,,mp3 player connected to a battery only..no audio connection.
and get it near the boom box, and you could hear faint noise. but nothing bad enough to overwhelm
the audio.