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i'm new to the forum. I have some problem to Connect this device with one single battery. I think the problem is on the connection of the max4466 electret. It has a common ground and it make me impossible the connection with the pam 8403 that have separate ground. Audio- and battery -. How can i Connect it properly? Maybe a diode? i attached an image. when i use these chips with two different batteries it works very well. Please help me enter image description here

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Do NOT use a diode. Just connect the grounds together.

In a larger system with shielded wires and ground connections that really include a ground (earth ground, that is) connection things are more complicated.

In your simple circuit all of the ground connections will be at the same potential, so just tie them together.

If you measure between the ground connections on the amplifier board, you will find that they are all connected together. The - connections on the output side are a different thing. The amplifier is a bridge amplifier, so the - side isn't ground.

Thanks to ricardomenzer for pointing out the bridge output of the amplifier.
That show once again that it is better for the question to include links to the datasheets.

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  • \$\begingroup\$ The multiple ground points are there for convenience in connecting the input, output and power wires, not because the grounds are "different" in some way. \$\endgroup\$ Mar 18 '16 at 16:51
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    \$\begingroup\$ I don't think that it's entirely correct. According to the typical application circuit in datasheet (diodes.com/_files/datasheets/PAM8403.pdf) the output seems to be connected in some sort of bridge amplifier (didn't read it enough to be sure), so the output "ground" (negative) is NOT connected to the ground. From the picture, I think this module is based in the circuit in the datasheet. To be honest, I think the module PCB is badly labeled. If I was the OP, I would check this circuit against the datasheet to check how things are connected. \$\endgroup\$ Mar 18 '16 at 17:10
  • \$\begingroup\$ @ricardomenzer: Thanks for the tip. I hadn't even realized that the model number of the amp was in the question. \$\endgroup\$
    – JRE
    Mar 18 '16 at 17:51
  • \$\begingroup\$ @JRE Me neither. I looked at the zoomed picture to find it. hahaha \$\endgroup\$ Mar 18 '16 at 18:00
  • \$\begingroup\$ To the OP: If it doesn't work when they use the same battery, it probably has to do with bias point mismatch. Try adding a series capacitor in line with the output of the mic amp board. Maybe a 10 uF ceramic cap if you have one. If you have schematics, post them. Then maybe someone will take the trouble to give you a good answer. \$\endgroup\$
    – mkeith
    Mar 19 '16 at 4:01

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