adding an audio line out on a PCB?

[2014fralit]

Hello,

does anyone here ever tried to add their own audio line out on a PCB? A bit like what's often done by Game Boy chiptune musicians to bypass the crappy headphone amp, essentially taping into the audio traces as close to the chip as possible (for the GB it's just after the RC filters I think).

[thegreathopper]

Yes, I have done that on a Neo Geo MV1C board, this board is mono but it can be modded for a stereo line out by picking up the signal before the amplified mono output.

I am sure it’s possible but will be different on each Jamma board.

[thegreathopper]

Here you go,

http://www.neo-geo.com/forums/showthrea ... orking-now

[pubjoe]

Iirc Mame reveals that about half of all arcade PCBs have stereo lines with nowhere to go.

[DaveyD]

Ive done one to my MV1B neogeo board. i made a little circuit on strip board, soldered wires onto a few points on the PCB, and then drilled 2x holes in the plastic case to fit a pair of phono plugs. It sounds loads better going through the stereo amp in my NAC, than using the pcb onboard amp

[2014fralit]

Thanks for the replies! And yes indeed the motivation is to have better audio. Right now I'm (super slowly) looking into (maybe) doing that on a Strikers II PCB. First of all because I'm really curious to hear how it sounds at the source. The sound on my board is not terrible, but it's definitively noisy (and it does not come from the caps, I've compared all their ESR values with new ones, and they're all good AFAICT).

I quickly checked the PCB and the soundchip is an OPL4 YMF278B which surprisingly is mono despite being quite powerful (FM synth + sampler). It has three pins for audio out, one for the synth, one for the sampler, one with both mixed together, that's the last one that's used on the PCB. I guess for the first step I will have to look/hear at what comes out of this pin...