Fitting a ground loop noise isolator into a GBA


Active Member
Dec 22, 2020
I always play with headphones on and when playing my GBA I would always have a slight but noticeable buzzing sound that you all should be familiar with, especially if you did the amplifier modification.
the dehum dehiss kit already provides a sort of solutions to this problem but i think that isn't nearly good enough. I can still hear the buzzing very clearly, especially through my headphones.
That's why I always carry a ground loop noise isolator with my GBA. And with it the noise is nearly gone, completely unnoticeable when ingame. But having to constantly hold it in the hand at the same time with the GBA gets cumbersome and uncomfortable after a while so i was wondering if it was possible to fit one of those isolators into the GBA, I've certainly not seen anyone else do it before.
I've taken one apart to get a better understanding of how the components inside are arranged and how well they could actually fit and from what i can tell its just two of these little coils and the 3.5mm jacks. The jacks wouldnt be needed if one were to mod it inside obviously so its down to those coils.
But that's about were my knowledge ends already. Looking at the PCB it looks like some pins of these coils are either completely unused or, more likely, the PCB has at least three layers where those remaining traces are. But i don't know jack about electronics so i would be glad if someone that does could chime in a bit.


Editorial Team
Nov 21, 2005
United Kingdom
Most usually look more at capacitors but if a ground loop isolator does the deed then can go in for that.
If you wanted to know how one works then
Short version there are three main components, though in this case one as you surmise.
Coils tend to refer to inductors which do get used to smooth out spikes but this is actually a transformer.
Most times you see transformers they are there to change voltage but here it is 1:1 which theoretically does nothing to the voltage, but will stop the induced noise by reasons described above. Transformers in their general form have two legs per side (you will get a resistance between them if you need to check) for a minimum for four, any more tends to be when you have multiple output windings (in normal times might want 120V for normal and then 5V to just power some simple electronics). Though you would have the idea of having to consider what goes for stereo here (you could merge but that would make mono sound) in which case the pin count goes to 8 (4 in, 4 out or maybe 6 as you could probably share a ground both sides.)

Your choices for install then vary.
You can desolder the headphone jack, insert the transformer there and then the headphone on the output. This is the virtual equivalent of the thing you have.
You can cut the traces leading to the jack, solder the relevant bits of the transformer each side of the break and go from there. Harder as a general action as you will presumably be soldering to traces (might be some vias and pins on the jack itself) but potentially easier to fit things in that way as the jack will not necessarily have much space nearby to insert things..

Option another. Why hold it when you can get some sticky back velcro and just put it on the back of the device. Might even make the jack point a sensible direction as well.
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