Isolation circuit ???

[PanheadJeff]

Gents,
I need help in designing a circuit that will isolate, or eliminate, the "feedback" that I get on the mp3 player I have on my motorcycle if I attempt to power it with a stepdown 12v/5.6v automotive transformer at the same time I have a 12vdc 100watt amplifier from Shark Radio powered up.
I have tried to run power directly from the battery to the stepdown transformer but no matter how I try to power the unit from the bike battery I get a "loop back" or "feed back" in the audio that sounds like someone is turning the volume up and down rapidly.
If I just run the mp3 player on it's own battery there is NO "loop back".
Is there a fairly simple, and small, circuit that I can build that will eliminate this "feed back" or "loop back" issue.
I would really like to be able to run my mp3 player off of the bikes electrical system so I don't have to constantly charge the mp3 player's battery.
BTW... my motorcycle is a 1950 Harley Davidson Panhead that I have owned since 1978. I converted the electrical system over to a 12 Volt system quite a while back and everything works great, EXCEPT this one little issue.

Thanks.
Panhead Jeff

 

[Resqueline]

Yes, in order to break the noisy ground loop, you'll need a step-down converter with galvanic isolation, something like the PST-DAA1205 that I found here.

 

[PanheadJeff]

Yes, in order to break the noisy ground loop, you'll need a step-down converter with galvanic isolation, something like the PST-DAA1205 that I found here.

Thank you VERY much. I've ordered that unit. Will come back and let you know how it works out.

Panhead Jeff