Pi in a Gameboy Advance Build - WIP

[moosepr]

@obsidianspider maybe try powering the amp from a different source, see if that stops and buz?

[backstander]

@obsidianspider
I don't know if this works but I read somewhere that you can edit /boot/config.txt and add the line "disable_audio_dither=1" and this should help with analog audio jack hiss issues. Worth a shot!

You might need to put a Ferrite Core on that cable. How it works: "magnetic materials absorb signal interference, reduce signal errors and improve signal integrity"

[obsidianspider]

@moosepr That worked, but long term that's not a good solution since I am putting all this in a Gameboy case. I did try adding a capacitor to the power side of the amp, but that had no effect. I may need a specific size, I dunno.

I saw somewhere (I forget where now) that connecting A- to GND would help with the hiss, and it did tremendously. It's not perfect, but WAY better. I also haven't gotten to RadioShack yet to get some resistors for the bridging to mono yet.

@backstander I am definitely thinking that I'm going to need some ferrite beads at least, as they're showing up all over on sudomod. The trouble is that no one locally has them, so I'll have to order them online.

I tried the audio dither thing, but since the input source for sound to the amp is from the USB sound card that didn't help.

Off to RadioShack to buy some resistors!

[moosepr]

@obsidianspider it does sound like is picking up the interference through the power then. Maybe wrapping the power lines round a ferrite ring like @backstander mentioned will help? Do you have any old motherboards or anything knocking about? You can sometimes strike gold with the little copper inducters

[obsidianspider]

Some investigation into using capacitors to clean up electrical noise prompted me to try attaching a 0.1 µF capacitor to the power input of the amp. I can't tell how much it helped, but that combined with the 10-Ohm resistors coming off the headphone jack to bridge the stereo into mono has sound that has a level of hissing that I would say won't bring this project to a halt, but I am going to look into buying some ferrite beads to use on the power input as well as the speaker output to try to help clean things up a bit more.

Next up it's a matter of the two things I've been putting off: The power circuit (soft shutdown, low battery warning/shutdown) or modding the case...

[thedudester80]

Why would you need a sound card for a Pi 3? couldn't you just wire into the headphone jack pins and get the sound that way? Or is that not possible? Anyway the project is looking fantastic BTW. =]

[obsidianspider]

@thedudester80 It's possible. I initially decided to use USB sound to try to reduce the hiss I was getting when I was doing some testing. The USB soundcard has zero hiss, and for how cheap it was, sounds really great with these old games. Considering that I'm getting some hiss with the Adafruit amp even with the USB soundcard as the source of the audio I'm not sure if it would be better or worse going right off the Pi. It might be worth trying things without the USB soundcard and saving that for my Gameboy Color project. I'll have to think about it.

And thanks for the kind words. This is a whole lot of figuring it out as I go, and I really have no idea what I'm doing.

[moosepr]

@obsidianspider ooooooh oooooooh oooooh lightbulb moment! Your currently powering the amp from the 5v input to the pi. What happens if you try powering the amp from the usb 5v output? Maybe that is cleaner?

[obsidianspider]

@moosepr it's worth a try. The amp itself is rated to pull up to 800mA at full tilt, it I'm running a tiny speaker and the whole system is only going to be getting 1A from the PowerBoost, so the fact that the USB ports only output 500mA max shouldn't be an issue. I think what I'll try is tagging off the power that's connected to the sound card, at the sound card. Since they'll both be next to each other inside the case that would also cut down on wires in the case if this works. I'll report back, but first, some coffee.

[obsidianspider]

@moosepr Going to USB for power has basically eliminated the CPU/disk access related buzzing! I did leave the 0.1 µF capacitor in there, as I figured it can't hurt. There's still a little bit of hiss from the amp (just general background white noise when no sound is playing), but I'm thinking some ferrite beads on the speaker wires will take care of that.

Now to read up on options for power circuitry…

[A Former User]

Up next: Pi in a DS.

[thedudester80]

I remember hearing something about using a capacitor for a hiss noise for your amp. I'm not sure what kind off the top of my head but it might be something to look into.

[moosepr]

@itsnitro Hahaha, I have already thought of that one!

[A Former User]

@moosepr Huh.
But here's the thing; RetroPie needs to be compatible with 2 monitors.
Cause ya know, the DS has two screens.

[moosepr]

@itsnitro yeah it wouldn't be a 2 screen job. More like the people who cut the top screen off a DS to turn it into a skinny square GBA

[A Former User]

There could be a way to remove the screen on the bottom and keep the one at the top, keeping the original shape of the DS. All we are doing is just removing the screen.

[buddyscott]

@itsnitro said in Pi in a Gameboy Advance Build - WIP:

@moosepr Huh.
But here's the thing; RetroPie needs to be compatible with 2 monitors.
Cause ya know, the DS has two screens.

Might be possible for a 2ds project then? If I remember correctly the screen for it is just one big one.

[A Former User]

There's a 2DS.
Still has 2 screens, but it would be considerably easier to fit everything inside. Just a thought.

[lilbud]

@itsnitro I believe the 2DS has 1 screen

[obsidianspider]

It looks like the 2DS uses one screen. If someone wants to put a Pi in one, let us know how it goes.