jamma vs stereo setup(konami)

darkcat1

Well-known member
Joined
Dec 19, 2011
Messages
4,102
Reaction score
49
Location
Winston, Georgia
ok guys it's time for the newbie's stupid question. I just got the machine fixed but it works on external audio for the speakers and they aren't wired for jamma. I have two older boards that don't have the audio out on them: Crime Fighters and TMNT and I was wondering how hard it would be to wire a Mono/stereo switch into the Jamma harness myself.

I will note that TMNT has the nubs on it where the four audio pins should be which is also an option if I knew where to find the part and could sauder it in.
 
Adding a switch isn't difficult, however I prefer the approach of having a 3.5mm stereo socket on the speakers. I solder a plug onto the JAMMA harness, connecting it to both left and right, and then make up cables for the different board pinouts using old CD-ROM analog audio cables.

This way you avoid potential damage to the amplifiers on your boards by forgetting to flick the switch to the appropriate position. It also gives you the option to easily plug in an external pair of speakers or an amplifier if you ever have the need.

The plugs on these type of cable are absolutely perfect for audio headers on PCB's and it is not hard to take the pins out & move them to a different location if necessary. A small screwdriver or pen works nicely.

_0.jpg
 
Last edited:
I've wired my horizontal and vertical JAMMA cabs for stereo/mono audio with a 4PDT switch.

This is a quick look at the bottom of the type of switch I use (sorry for the rather primitive MSPaint artwork):
switchk.jpg


The speakers are wired to the center row of pins, as shown. I then create jumpers so that the switch avoids damage to the amps on my boards.

When the switch is set in the "stereo" position, there is 8 ohms resistance on the left and right channels. When set in the "mono" position, there is 4 ohms resistance because the two speakers are wired parallel. This is within the specs for all the amplifier circuits I've seen, there hasn't been any damage to my boards when the switch is in the wrong position. The worst I have noticed is the audio seems out of phase if it is wrong.

Stereo wiring is per the NEO-GEO MVS and mono is per the standard JAMMA. I then have made modifications on my boards that have stereo output to run the left and right audio directly to the JAMMA connector. (I know that could cause an uproar with some people, but I have no intentions of ever selling my boards so...)

Brian.
 
Back
Top Bottom