/documents/gameboy mods/GBCAudioMod:

Nintendo Game Boy Color: "Line Output Mod"
(commonly known as "Pro Sound Mod", we have yet
to figure out where that name came from)
(Original modification discovered by Trash80)

1 foot shielded pair wire
2” solder wik
soldering iron
tri wing screw driver
2 size proper shrink tube
heat gun or lighter for shrink tube

While modifying the GameBoy Color to have a louder and better bass response is not exactly a new concept, I felt the info out there was lacking.. So here is my rendition with a bit more technical thought put into it. (all images open into a new window with expanded explanations and larger photos)

Take a listen to the difference in sound!! This was recorded direct with no change in input gain. I added the vocal parts :)

At first glance the GBC (or CGB) has a slick design, coming in many colors. It boasts a crisp color screen that (when well lit) is a lot easier to work with while making tunes on LSDJ or Nanoloop. Turning the GameBoy over you will find the typical “Tri-Wing” security screws that Nintendo is so famous for using. I will start by saying this. “DON’T WASTE YOUR TIME, GO AND BUY ONE!” You’ll spend more time trying to get a small flat head or nail (filed down) to work than it takes to write a song for the first time on LSDJ. You can purchase these screw drivers from many places for well under $10. Check out MCMinOne for their version coming in at a whopping $2.99 +shipping. While you’re at it, purchase some accessories (including NES 72pin headers for only $10.39, much cheaper than the other “game system repair” sites that sell them for twice that!!!) for Nintendo gear by searching for “Nintendo” . Ok enough of the rant ^_^

***Warning! Remove any static charge by touching a good ground source. Do not attempt any of these mods in socks. I cannot be held responsible if you fry your GameBoy because you didn’t take proper precautions. Proceed at your own risk****

Remove the six security screws (2 in battery compartment). Making sure there isn’t a game inserted in the gameboy you should now be able to remove the back cover of the gameboy, exposing it’s naked innards (if your GameBoy isn’t transparent then this is a new site for you).


Next locate the volume pot. This is the point at which the audio is passed through it’s first gain stage post the micro. This is where we shall get our “Pro Sound” or closest to line level full fidelity audio signal. While being louder and having better low-end response, it kicks out a little bit of noise when audio isn’t playing due to it’s amount of gain at this point. And even though it’s louder it’s impedance far more different than the original headphone output impedance. Thus it cannot drive headphones at this point. But line level and instrument level inputs work great!!!

Next Locate the small surface mount trim pot in the middle of the main board. This actually adjusts the contrast (from what I can tell) of the screen though it’s pretty much all the way up so you can see well stock. So I don’t advise playing with this… Anyways, next to the “contrast pot” are 3 small surface mount components labeled “EM2, EM3,& EM4”. Since I am unsure of what they are.. they could be resistors (so small there wasn’t an part ID on them) but I didn’t measure across to find out.. it would make sense though if you understand how output stages work.

EM2 and EM3 connect to the headphone jack to make connections to LEFT and RIGHT outputs. While EM4 is connected to the Normal of the headphone jack that switches the internal speaker on and off. I think it basically controls a switch somewhere that when it goes low it shuts the speaker amplifier off. Just a guess though.

Remove the Ribbon Cable that connects the display board to the main board from the LOCKING header. To do this you have to pull the tabs on either side out so they unlock the header and the ribbon slides smoothly out of the header. Remove the 3 standard Phillips screws to remove the main board from the body of the GBC.

Turn it over, make observations, look at the little power supply board off the to left, the power and headphone jacks, control pads, etc. While you’re here you mght as well clean the buttons and pads so that it ensures another 10 years of functionality.

Look at the Headphone jack and notice that its pins are labeled (P5Lout&P5Rout). In this modification we are going to be keeping everything physically stock and using the headphone jack as our output source. You can install a cable that goes to ether an 1/8” or 1/4” TRS cable plug if you want to reduce stress. But in this example I am doing everything internal.

Now that we have identified the locations of the board that we need to address lets do some prep work! Cut your shielded pair wire to about 7 inches (this will get shortened later). On one end strip back about 5/8” of the insulation, cut the wild shield wires, tin the shield and put some shrink tube(all had was clear but I darkened it so you can tell the difference between the two wires) around it to isolate it from any thing around it. Then strip and tin the white/clear and red wires. I cut mine back really short because we’re dealing with surface mount parts and your surface area can’t be very large when tacking wires on to mounted components. I then put a piece of shrink over all 3 wires to ensure the shield doesn’t bridge/short anything on the main board. Both ends will eventually look like this.. The only difference is one end will not have the shield dressed out (avoids ground loops).

Solder the 3 wire (L,R,Shield) to the volume pot and dress the wire across and as close to the main board as possible. De-solder the speaker wires from the main board and remove the speaker. Yes I know this sucks, because we all love that wonderful piece of monitoring equipment (laughs). But we need to make room for the output wire. Now if you absolutely MUST have the speaker than you can spend the hours it will take trying to dress it around the buttons on the front panel to get to the output jack.

We will be running the output wire along the right hand side (left hand if we’re looking at what would be the back of the main board (cart side). I cut small notches out of the plastic speaker frame to make room for the output wire to run smoothly around the corner of the gameboy then under to the output jack. Shorten the wire to a length you feel is proper slack and dress it out as stated above but removing the shield wire from being dressed. Solder (while keeping phase in mind) to P5Rout and P5Lout points on the Jack. It should look something like this.

I left a more slack on mine and curled it up in the speaker corner. I then carefully placed the main board back in the case dressing the wire under the main board then curling it around then across (as mentioned above). This is hard to describe but look at the image below to see what I’m talking about. Watch out for getting the output wire too close to the “B” rubber pad/button. It wlll fit with enough clearance to allow the button to function properly.

We’re not done yet!

Screw the board in place (three Phillip screws) and relocate the “contrast pot. Remember those three components labeled EM2,EM3,EM4? Since we bypassed the headphone amp all together we need to isolate the headphone jack so that we are using the new output mod. Remove EM2 and EM3. If you don not you will get a very weak signal output. Defeating the purpose of this modification.

Next we want to remove EM4, this will break the normal contact so the micro thinks a jack is plugged in all the time.. since we removed the speaker we do not want the headphone amplifier to run with out a load. So this shuts it off since we aren’t using a speaker anyways.
Clean off the pads that the components were on with some “Solder Wik” just to make sure it won’t bridge at any point due to messy solder pads.

When it’s all said an done it should look something like this…

Double check that everything is seated properly and reconnect the ribbon cable (don’t forget to lock it in place). Place the rear cover on carefully (making sure the power switch is positioned correctly) and screw in a couple screws to hold the back on, test that your modification actually works. If it does, CONGRATS!!! You now have a much louder, more full sound that will be just about as good as a gameboy classic. If it didn’t work, go back through and double check your work. Make sure you didn’t bridge anything up by the volume pot. This is a heavily populated area and things can easily get messed up there. Minimal Solder is Key!!

If does work, re-install all the screws and make some tunes!


I hope this tutorial was helpful, if you have questions you can email me and I will try my best to help. If you are uncomfortable with doing this mod, I offer pre-modified GameBoy colors for sale, or I can install the mod on your GameBoy for $43 (includes return shipping) but you have to send the GBC to me. Good Luck!!!