/documents/gameboy mods/GBClassicAudioMod:

Nintendo Game Boy DMG-01: "Line Out Mod":
(commonly known as "Pro Sound Mod", we have yet
to figure out where that name came from)

(Original modification discovered by Trash80)

When I heard the rumor that you could get the output of the gameboy classic to be louder, I jumped at the chance to do so. I knew there wasn't much info on it since I hadn't come across it yet on the web.. So I decided to document it so that those who want to do it can read this how-to and obtain a gameboy classic that kicks out the beats just a bit louder than others with very little effort involved. Click images for larger view.   So lets begin:

Behold a piece of chip history (Laughs):
Modified in 2001: 1/4" TRS Female Jack

***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****

Parts:
(1) 2pair shielded wire (small gage)
(1) Tri-Wing Screw driver
(1) TRS Female plug (optional)
Solder
Wire cutters
small and medium sized shrink tube
patience
care

Procedure:

Step 1:   Opening the GameBoy Classic

Flip your gameboy over so that the battery cover door is facing you. Open the battery compartment and set the Bat. Door to the side. Now all 6 tri-wing security bit screws should be exposed. Remove them.

Step 2: Separate Top from bottom
Unlock the small ribbon cable at the top of the PCB, and slide the cable out of the header. Be careful not to bent the cable too much. This is the main feed to   your display we're talking about, so if you care about it... be careful!!!

Step 3: You will find the volume pot on the battery compartment side. This modification is very similar to the Gameboy Color mod, but the pot is backwards. So if you want to have output volume/gain control you'll want to wire to the lower side of the pot. See picture below.   Prep your single pair shielded wire for wiring. One side will have the shield dressed out for wiring to ground, and the other side it can be cut off to avoid ground loops.

The side with the shield dressed out will be connected to the pot. Note polarity so when/if you pan things left and right they actually come out left and right ;)   Be careful not to make and shorts. Be sure to tin your wire and apply a little extra solder to the pot terminals so that they connect very quickly when reheated. It should look something like this....

Step 4. Take a look at the output jack at the bottom of the chassis. There are 4 wires going to a small PCB that has the headphone jack attached. We are going to use this jack for our output. **note** you can install an external jack if you want to keep the headphone jack available. If you keep the mod internal you will not be able to use headphones as we are bypassing the output amplifier that allows enough power for headphones. The modification is for a louder output that is closer to line level which headphones will have an impedance mismatch to the point where the headphones will just sound super quiet. If you are installing an external plug, be sure to secure the cable from being pulled our or pushed back into the gameboy.

For the internal modification all you need to do is cut the two far right wires (if the cart slot is closest to you) which are the output from the headphone amplifier. I removed them completely so they weren't dangling around inside.

Now take a look at that 4 wire connector that connects the output board to the main board. From left to right the connections go: Switch normal (the line that cuts the internal speaker when you plug into the jack) Ground (GND), Right output, and Left output. These are you points that you will solder your shielded cable to (Right/Left output). You might be wondering why I chose this spot instead of directly to the jacks. And to answer this question, it's because there are output de-coupling caps on this board which will assure no dc-coupling issues with other gear. It's just a precaution. I have tried soldering to the jack and to these points and found there to be no different in audio quality so it's safe to use these points. Watch for shorting when soldering. Again, pre-tin your wires and solder points for a cleaner job.

It should look like this...

Step 5: Dress the wire so that it doesn't get pinched when putting the gameboy back together. Test your output by reconnecting the Display ribbon cable and playing a game or a track. Check polarity as well. Remember, you're checking with a line level input not headphones. If it works, CONGRATS!!!! J your gameboy classic is now a lot louder and will punch a little bit better. If it doesn't work. Double check your work and read through the steps again.

If you choose do do the mod externally there are some slight differences in the wiring. Both sides of the cable you are install must have the shield dressed out (the shield on the output side will get soldered to the casing or ground point on the plug). And the only wire you need to clip on the output board in the GameBoy is the white wire (which is the normal for the internal speaker). This will deactivate the internal speaker so you don't have to have something plugged into the headphone jack if you are using your external output. It will look something like this...

So if all goes as planned you should now have a Pro Mod'd GameBoy. Sweetastic!!! Feel free to email me with questions should have you have them!

And if you get really clever, install a footpedal jack to hit the start button remotely! :) it's great for starting a track with your feet if you are using your hands for something else! I might do a how-to for this but it's really simple. just trace the start button pads back to a spot where you can solder wires to. the wire them like you wired the external outout :)