CPS1 "Stereo" from pre-Q-Sound A Boards

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NoAffinity
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CPS1 "Stereo" from pre-Q-Sound A Boards

Post by NoAffinity »

Thought you guys might enjoy this. I saw an old post on Neo Geo forums saying "just connect via CN5 and you get stereo sound from your CPS1 A board", not much more information. I saw a couple other posts across other forums saying "I saw this post on Neo Geo forums, but all I'm getting is muffled audio that is in no way stereo sound". So, I thought I'd give it a try. Made an adapter, plugged it in and the sound was crap. You can kinda hear the game sounds, but right is louder than left, and it was unimpressive at best.

So, I stared at the CPS1 motherboard schematic for a while, and it sure looks like the intent is there to provide 2 channel sound via CN5. Well, the key is removing VR1. :awe:

1) Make an adapter from a PC case fan plug spliced to a stereo 3.5mm connector

Image

2) Connect adapter to game board and to an amp. I hooked it up to my Q-sound amp, and used this Radio Shack volume control adapter, with 3.5mm in and 3.5mm out. If you are hooking up to an amp that has volume control on it, then you obviously don't need something like this.
Image

3) Enjoy “stereo” sound from CPS1 games that support it. It is not true stereo but is a nice upgrade from JAMMA mono. Music effects are split between the channels. “Big” hits come out through both channels and create a richer effect. Bass is a bit heavier. 1P character select sounds are on the left channel, 2P character select sounds are on the right channel. Those are the things I noticed. Kinda fun! My camera phone didn’t capture it well, but this is it in action:

https://youtu.be/3im2etdaVXw

Note that once VR1 is removed, you will not get audio through the JAMMA connector. So, it's either JAMMA mono or CN5 "stereo", but not both simlutaneously. If someone can stare at the CPS1 A board schematic longer than I did and see a way to have both going simultaneously, please post.

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Re: CPS1 "Stereo" from pre-Q-Sound A Boards

Post by RMRM »

Cool info here, thanks for sharing :slowclap:
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Re: CPS1 "Stereo" from pre-Q-Sound A Boards

Post by wigsplitta »

Cool info indeed. I've always used an amp with adjustable Left & Right levels for my Stereo CPS1 setup up until now.
I'll being giving this a go in due course 8-)
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Re: CPS1 "Stereo" from pre-Q-Sound A Boards

Post by Flinnster »

Not sure I'd be willing to start removing the volume pots from my CPS1 boards. However lifting a pin and fitting a small on/off switch would probably work quite well. Interested... Ghouls n Ghosts stereo? Yes please :)
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Re: CPS1 "Stereo" from pre-Q-Sound A Boards

Post by NoAffinity »

The on/off switch is a good idea. :awe:

I went ahead and captured some direct feed of GNG and SF2 HF. Below is the supported game list. GNG not on there, and I don't notice anything different from L and R. SF2 HF, however, you can certainly tell musical instruments are more on the L and percussion is more on the R.

Anyway, enjoy!

GNG direct feed capture: https://youtu.be/ojk19Lo-oKg

SF2 HF direct feed capture: https://youtu.be/1vMTSlAtNg4

Supported game list. This is the only list I could find before posting just now, but I saw a longer list a couple days ago. If someone can find that longer list and post it, much appreciated!
http://www.neo-geo.com/forums/showthrea ... post133483

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Re: CPS1 "Stereo" from pre-Q-Sound A Boards

Post by NoAffinity »

I went back and listened to the audio from both videos, through head phones. On GNG, right is slightly less audible than left. I send my various audio feeds through a DJ mixer, which has a volume level indicator for each channel, on the main volume fader. It was showing that right was one "tick" below left at all times. When I was running SF2HF, that indicator showed left and right as being even. You can hear the difference in the music pieces coming out of each channel, while action sounds, voices etc come out of both channels. I am confident that the setup was good on both captures, and it is not anything to do with my cabling, connections, etc. The only difference between both captures was the B+C set, all else was equal.

So, it seems that if the game does not offer stereo, then there is a disadvantage to using CN5 output. Can anyone with good knowledge of audio circuits confirm that this would be true, based on the above schematic? (the whole schematic is here, if other pages are needed: http://www.jammarcade.net/files/Schemat ... vision.pdf) Then again, maybe it's not in the circuitry, maybe its in the code. :think:
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Re: CPS1 "Stereo" from pre-Q-Sound A Boards

Post by Nebula »

NoAffinity wrote:The on/off switch is a good idea. :awe:

I went ahead and captured some direct feed of GNG and SF2 HF. Below is the supported game list. GNG not on there, and I don't notice anything different from L and R. SF2 HF, however, you can certainly tell musical instruments are more on the L and percussion is more on the R.

Anyway, enjoy!

GNG direct feed capture: https://youtu.be/ojk19Lo-oKg

SF2 HF direct feed capture: https://youtu.be/1vMTSlAtNg4

Supported game list. This is the only list I could find before posting just now, but I saw a longer list a couple days ago. If someone can find that longer list and post it, much appreciated!
http://www.neo-geo.com/forums/showthrea ... post133483

1941
Adventure Quiz Capcom World
Adventure Quiz Capcom World 2
Street Fighter II (also CE, etc.)
Strider
UN Squadron
Captain Commando
Hi, did you find longer list of available stereo cps1 games? I just perform a search but I cannot find any more apart of list that you provided.

Maybe I will give a try using an A Board to put it a small swith to enable/disable the volume pot with my SF2/Captain Commando
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