The audio signal is too weak to handle speakers. You need to amplify it so you can output some significant sound.
The reason you can hear your GC through your TV is because the TV has an amplifier and does that for you.
Sent from my GT-I9500 using Tapatalk
10k is to much to dim an LED the resistance you probably need is about 470 ohm so 1k pot should work. But I would suggest 2k pot just in case you need more resistance.
Sent from my GT-I9500 using Tapatalk
The mod chip is called wiikey fusion. It's designed for the wii but it will also work with some Gamecube. http://forums.modretro.com/viewtopic.php?f=36&t=6003
Sent from my GT-I9500 using Tapatalk
Actually the outer drum form the female jacks ARE GROUND. I know this for a fact, I've been working on a RCA related project. If you don't ground them the image will stutter and may damage your TV.
Sent from my GT-I9500 using Tapatalk
The dimmer LED is being undervolted and the brighter is working at its optimal voltage. Try adding any resistor below 1k, that should do it. If you want a better prediction try measuring the current of both LEDs or you could use a potentiometer to estimate the perfect resistance you need and...
Do you have specs for your LED? I think that the best way is for you to buy a potentiometer (variable resistor) and place it in one of the lead of the LED. The start turning it slowly until it's the perfect brightness.
Or just try adding a 1k resistor where the potentiometer would go. If it's...