Question on Speaker output, MVS vs. JAMMA!!

Hey all! I'm currently nutting out some improvements and additions for my upcoming MKII version of my recent Supergun (pictured below and posted a while back) and I have a query on the amplified audio output of standard JAMMA PCB's vs. the Neo MVS multi-slots. I'm just sketching some wiring diagrams and have come to the spot where I want a toggle switch for MVS stereo vs. JAMMA mono audio. Standard JAMMA outputs the primary (+) speaker signal from pin '10' on the component side and the (-) from the solder side of the PCB at pin 'L'. I'm concerned that pin L (speaker negative) doesn't appear to simply be a direct GND connection and tends to come from the audio hardware the same as big brother (+). Is it safe to use a direct GND connection for speaker (-) on a JAMMA mono rig? I'm not too knowledgeable on audio stuff and the inner workings of speaker cones etc, I'd hate to think I'd be damaging the audio amps on my PCB's over time by using direct GND rather than speaker (-). I remembered NGT's famous (but rather shoddy hehehe ) MS Paint rendering of Supergun wiring. He's used a direct GND source for both MVS stereo and JAMMA mono (-) connections and ignored pin 'L' on the standard JAMMA version. Can I get confirmation from any o yo audio hardware maniacs out there (and NGT himself!!) that this indeed perfectly acceptable and not detrimental to my precious PCBs.

PS. Love those ham shaped RCA jacks, bang up job son lol

Heres the thread -

http://www.neo-geo.com/forums/showthread.php?t=81108&highlight=supergun+wiring

"Is it safe to use a direct GND connection for speaker (-) on a JAMMA mono rig"

No it definately is not safe, most jamma boards use a boot strapped audio output stage. Speaker - is not grounded. There are some exceptions btw.

Check out the circuit diag of the HA13001 (as used on mvs boards) in mono and stereo config and you may see what I mean.

boot strapping /lacing increases the efficiency and potential output of the device.
Notice from the HA 13001 specs.

Stereo 5.5W/ch = 11W total

Mono BTL = 17.5W

You can achieve typically 50% more power output.

No jamma boards I know of are grounded on pin L (of course I'm not talking about stereo MVS). In a supergun setup if you try and connect pin L to the TV (or receiver) jacks, which are grounded, you'll only hear an awful noise. If you want to get sound you *have* to ignore pin L (leaving it unconnected) and run ground from the PCB to the TV/receiver jacks. In a cab you'll want to use pin L and not ground instead.

Im sure some jamma boards have L grounded, I cant remember which ones.
Will check my boards, maybe Toaplan, Truxton maybe ?

John_Smith said:

I want a toggle switch for MVS stereo vs. JAMMA mono audio

Click to expand...

Instead of a switch you could add a third jack, so when you're playing MVS you use the 2 stereo jacks and when you're playing a Jamma game you leave'em unplugged and only use the mono jack (which can become dual mono with an adapter):