Not sure the best place to post this, but I guess it's here. I've got an arcade build in progress, the electronics of which can be seen below. It's a dual switchable system, combining a JROK jamma board and a Raspberry Pi. The problem I've got is that the audio from the Pi via the headphones is extremely noisy, and contains all sort of interference. I'm not expecting high fidelity sound of course, but the noise is way, way in excess of what I'd expect.
myarcadeboard by
Tom D, on Flickr
The parts, as numbered are:
1. 6PDT switch with 3 connections: it switches power to the pi/jamma, and audio L R from the pi/jamma to the amp. Green wire goes off to the 5V switching PSU.
2. Amp, taken from some Logitech PC speakers. Powered by its own 9V supply (blue/white wires). Red/Yellow/Black are speaker cables.
3. iPac2
4. Raspberry Pi with VGA hat
5. Input from the control panel, inputs go through diodes to both the jamma board and iPac
6. JROK
7. Scanline generator
As you can see, ground is common and daisy chained around. When I'm using the Jamma board, the sound is perfectly acceptable. when using the RPi, there's way too much interference. Any ideas what I can do to sort this out? There's no way the headphone out should be this noisy, so I must have done something bad.
Reading other threads elsewhere indicated to me that the problem could be the ground wire to the Rpi is thin and long, and therefore has too much resistance? Though I don't know why this would impact the audio. Or is the Pi simply too close to the amp?