its like a tin foil hat for your gba

That's how I discovered it, too.

Something funny is that on one of my old GBAs it doesn't have a battery cover that will properly stayed on.  One day I had my finger resting in the battery compartment and I noticed that if I touched the right spot it would eliminate some of the hum.  I guess accidentally I discovered what Oliver has shown here. Hahaha, go figure!

Added the external version to original post. Probably the simplest mod ever. I recommend to try this first and see if it makes a difference. Works great on both my GBA units.

Is aluminium foil better than electrical tape ? I was thinking of covering the wire and speaker with a double layer of electrical tape.. What do you say ?

I really appreciate these solutions oliver!
Thank you so much!

That is clever Will try it out ASAP

Besides the hum (see noise filter mod), the GBA often suffers from a little high pitched whine. This annoying tone can be almost eliminated with a grounded shield near the audio amp.

This can be done internally and externally.
The easy way:

(be careful not to short the battery contacts)

(Foil sticked flat on the case with some adhesive tape.)

DONE!

If this works for you, you may consider the internal version:

Cut the foil into a square of about 3x3 cm with an appendix of 8 cm as shown here.

Insulate the square with a slightly bigger adhesive label.

Open the GBA and fold the PCB up.

Put the square on the PCB under the speaker and hold it in place with some tape.

Carefully flip back the PCB and fold the appendix up.

Put some insulation on the PCB, fold the appendix towards the screw hole marked with the arrow. Fix it with some tape so that the foil is right at the hole.

Fix the PCB by tightening the screws again. The screw in the hole marked red goes through the foil.

Before closing the case again, you may apply the noise filter mod to minimize hum, too: http://chipmusic.org/forums/topic/19565 … olderless/