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Solved: Audio Ground Loop Problem — Parallax Forums

Solved: Audio Ground Loop Problem

ercoerco Posts: 20,256
edited 2017-05-24 05:59 in General Discussion
I think it's ground loop. Have a serial-controlled MP3 player module connected to a Veho-style mini amplified speaker. It works perfectly. BUT I'm building this into a project, and I need to change the amplifier power to the same 4.5V supply as the micro and MP3 player. So I route the + & - wires previously to the LiPo to the same 3X AA cells as powering everything else. Works but there's a high-pitch whine (only) while MP3 files are playing. Then I disconnect the - wire and there is still power and the whine is gone but there's distortion .

Anybody got a quick solution or idea?

Comments

  • ercoerco Posts: 20,256
    The plot thickens: the interference/whine is originating in an HC05 Bluetooth module which I may not even need. I just wanted to have everything in this one. Quick solution is to delete the BT module, but I'll try a different amplifier first. 386 to the rescue?
  • ercoerco Posts: 20,256
    edited 2017-05-24 16:09
    Case closed! Different amplifiers work without whining, so Bluetooth remains in. Gordon laughed when I bought my LM386 modules, but they worked fine. So did my Dollar tree ball amp. See guys, hoarding pays off!

    FYI, there are right ways and wrong ways to merge stereo signals into a mono signal for an amplifier. I used this one from http://www.rane.com/note109.html and it worked fine with my LM386:

    n109fig2.gif
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