Line level (unamplified ) audio from Jackie Chan arcade boards
Tags: [arcade], [modding]
The Jackie Chan fighting game arcade boards produced by Kaneko (Kung Fu Master and Fists of Fire) both only output amplified stereo audio output - both from the Jamma header and from a 4-pin header on the motherboard near the amplifier heatsink.
Many arcade cabinets and supergun setups these days prefer unamplified, line-level audio, and here's how to obtain it on these boards.
The trimpot to the right of the image adjusts the level of the amplified audio - or more accurately, it adjusts the level of the audio input to the amplifier. I believe the input to this trimpot is roughly line-level, and so suitable for our needs.
If we say the pin on the trimpot closest to the edge of the board is pin 1, then:
- pin 1 is unknown functionality
- pin 2 is GND
- pin 3 is post-trimpot (attenuated) R audio
- pin 4 is post-trimpot (attenuated) L audio
- pin 5 is R audio pre-trimpot (line?)
- pin 6 is L audio pre-trimpot (line?)
- pin 7 is unknown functionality
If you want control over the volume on the board, then tap pins 3 and 4, otherwise 5 and 6.
There aren't any great places on the board to mount the jacks, unfortunately - in this case I had some which wedged into the heatsink fins pretty much perfectly though. Whatever works...
For those interested, the power amplifier is a Toshiba TA8210, with a pretty reference implentation surrounding it (as seen in its datasheet).
« Previous Next »