Supergun - CPS2 QSOUND Power Draw

So awhile back I noticed the sound went out on my Supergun. I didn't use it much at the time since I didn't have a proper kick harness, just a cobbled together one from an old floppy cable. The wiring was a spaghetti mess, etc. Well I decided to buy a new harness and rewire it all.

So I ripped out the old wiring from the big box that is my Supergun. All the wiring to the controller and video ports was done to terminal blocks and didn't need to be removed or anything. So I hooked up the new harness, tried out my NeoGeo board. Still no sound. I tried everything with the speaker wires, removed the RCA phono jacks, wired straight to a RCA audio cable, etc. Nothing worked.

Well as the title suggests, I took a tool to measure the voltage of the jamma edge connector with the power supply on. +5v, fine, -5v, fine, +12v, nothing. I thought at first it was a bad connection between the new harness and the PSU. Later I remembered I should check my fuses. That was it, the +12v line has a 2 amp fuse and it blew. No big deal, I threw in another and it was rocking again.

So I started up my CPS2 game Msh Vs SF and cranked the QSOUND volume to the max and after less than a minute the sound goes out, and I noticed when i first started that I could heard the CPS2 fan running which when I had no sound I didn't hear it either.

So my question here is does anyone has any idea how much the CPS2 with QSOUND cranked to max draw off +12v? More than my 2amp fuse for sure. For now I'm sticking to the Mono Jamma audio at a reasonable volume with the volume amped on the sound system instead.

I just wanted to share how this drove me crazy when I couldn't figure out why the sound was dead. I had assumed because my RCA Phono Jacks were loose that they spun and broke a wire. This assumption into what was wrong had given me tunnel vision as I didn't really consider other options. I should have read my Street Fighter 2 manual's trouble shooting which even suggests if you have no sound to check the +12v.

Atleast it motivated me to buy a real cps2 kick harness and rewire it half decently.

 

Since you're using a Supergun it should draw next to nothing without loading the JAMMA power amp. 12V is probably used for filtering/mixing op amps too but they won't consume significant current at all. 2A on the 12V rail would be enough to drive two speakers so something isn't right.

 

I think at the time I had both QSOUND and Jamma Sound connected. I had the QSOUND volume cranked to the MAX and I think I had the Jamma volume maxed too. Also the CPS2 Cooling Fan runs off +12v as it stopped when the fuse blew and resumed when the fuse was replaced. So does this still sound strange?

 

Yea.. What is your circuit for the JAMMA sound? Did you just attach a speaker or did you make an attenuator for line level audio?

 

For JAMMA edge connector sound, I connected Speaker - to the Ground of a standard RCA Phono Cable and Speaker + to the Center of the cable. Nothing fancy at all. I plug the RCA phono plug into a basic sound system that has its own volume control.

As I said, when the fuse blew I had cranked the volume on the QSOUND (QSOUND was enabled and outputting sound) and was using the sound system's volume to adjust the desired hearing volume. I don't know if I had the jamma exdge sound hooked to anything when it happened.

Pretty much my SG looks like this:
PC Power Supply for +5v, -5v, +12v, Ground. Fuse holders wired between the harness and +5v and +12v. Sound wired as mentioned. Controller ports wired to the harness. RGB Video wired to a VGA style connector which goes to a Sony PVM monitor. That's basically it, bare bones. No video encoder for NTSC or special amps or anything.

 

You shouldn't really run the sound direct like that, though - as Calpis said, you want line level audio. You're sending amplified audio to an input that's expecting an unamplified source. Why would you need to have the volume up to max, anyway? Have you ever heard an arcade machine on max volume? It's almost unbearable!

For your equipment's sake, attenuate the signal!

Are you sure your PSU is OK BTW?

 

Yeah it's not a good idea to put amplified audio on the line level input. While the audio input resistance is large and game boards don't have high power amps 1) every input isn't guaranteed to have automatic gain control so I guess some amplifiers will heavily clip the signal unless the volume pot is turned way down which in turn means more noise and 2) if the JAMMA output is up to 17Vpp (using -5 and 12v rails, not likely) that's a lot more than the 0.45Vpp defined for consumer line level. Say the line input is just an unprotected IC running off 5V, that high voltage could break down the input (which normally keeps current out) and allow it to be fried or worse.

Since games will typically use at least +-5V (10Vpp) for amplified audio, I'd attenuate that to 0.5Vpp, so a 20:1 resistor divider would do the trick. Also some amplifiers might not like (I mean they'll be fuming mad) having (-) directly tied to GND if they use the -5V rail or generate a negative rail. I think the solution to this would be to use 3 series resistors (big, small, big) from (+) to (-) and tap line level from the middle one. To be even more safe I think you could use some series resistors from the tap points to the line input. Edit: yup, this is what you want: http://upload.wikimedia.org/wikipedia/commons/7/74/T_type_balanced_attenuator_circuit.jpg

Back on topic: I can't say I'm familiar with CPS hardware with QSound, does it have digital volume control or do you mean the volume pot on the game controls the stereo line output too? I'd have thought it would just attenuate for the fixed-gain JAMMA power amplifier and the stereo outputs would be tapped before since they're supposed to go to a separate stereo amplifier in newer cabs.

 

To be clear, I had the board volume cranked, that one time. Since then I have the board volumes extremely low and use my cheap sound system to adjust the volume. If the sound system dies, I don't care. Only the boards matter.

I'm not sure what you mean by is my PSU OK. All I know is I probed the edge connector and got all the correct voltage readings. And everything works fine right now. No problems since. I just thought it was odd that my 2 amp +12v fuse went boom.

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I'm not sure what you mean by line level and all this all that stood out was potentially going back to the input (the jamma board right?) and damaging it. But as I said, now I keep their volumes low and adjust it on the speakers I have. It's just a basic sound system. I could just connect standard speakers to my supergun if I have to. I have two spares from an old CD/Radio/Cassette Deck.

CPS2 boards have a digital volume control. This is both valid for adjusting QSOUND RCA jack output and Jamma Edge Mono output. I don't think the CPS2 has a volume pot like my CPS1 (SF2) board does. The NeoGeo also has no pot, it uses slider volume controls. The CPS2 I think has built in buttons on the Mobo for volume adjustment but also there are wires on the kick harness connector for adjustment.

 

You probed it under load? PSUs can look fine when they're not under load, but not actually be fine.

I used to plug my guitar into an old valve record player I have. It gave the most dirty distortion sound, even at low volume. Of course, the reason it did that was because the high output of the pickups was overloading the amp. Similar sort of thing, really.

You can buy attenuators for car audio (putting speaker level outputs into an amp) - any decent car spares / car audio shop will sell them, as will big electronics places. Try Radio Shack or MCM. They'll probably only be a few dollars.

 

Line level is the unamplified audio signal, it has a very small amplitude and practically no current is transferred from an output to an input. All of the audio information is in the voltage. A power amplifier will take that small voltage, and increase (multiply) it by a certain amount (limited by the amplifiers positive and negative rails) and use that voltage to drive a speaker, a lot of current will be transferred because speakers are only 8, 4, 2 ohms. To increase the volume, the amplifier increases the voltage which increases the power dissipated through the speaker. Sound works logarithmically so each slight perceived increase in volume is actually TWICE the power used. Max volume draws a lot of current.

Line input is the input on your power amplifier (TV, stereo, whatever).

So the key thing here is that the speaker (-) terminal is not the same thing as GND, on many boards it may be, but if a game brings (-) to a negative voltage and that terminal is tied ground, there is nothing stopping current from flowing from GND into (-) and the amplifier can only handle so much current flowing through it.

That explains it if the digital volume control also increases the JAMMA output. Since you have (-) tied to GND, even if nothing is connected to the JAMMA speaker outputs, you are still drawing current. Since the 12V supply blew my guess is that the CPS2 takes the 12V supply and creates a -12V out of it to use with the amplifier. Even though they are now different "supplies", the 12V really supplies the current for the both of them.

BTW, a slider is one type of potentiometer, they take many shapes but they all work exactly the same.

 

I didn't check the voltages under load but I could do that. But I'm not terribly worried.

My Speaker (-) is not tied directly to ground unless the PCB actually ties it to ground. And I don't believe it should have been when the fuse blew, however the original fuse that blew that could have been the case but I'm not sure.

It sounds though like ideally I should use regular speakers for output so there is no risk to the board from any amplifier current going back into the board and damaging it?

 

You can use a speaker without amp... or just use an attenuator.

I just happened to be looking for some parts to rewire my friend's car audio system, and came across this:

http://cgi.ebay.co.uk/Speaker-2-RCA...844?pt=LH_DefaultDomain_3&hash=item4154ba0acc

If it's running fine now, your PSU sounds OK.

 

Your display's GND is still GND.

You can move the RCA's GND from (-) to the JAMMA GND, then there's no chance of damage. If you leave the (+) as it is the sound may be distorted depending on the JAMMA amplifier's topology so you can either buy an attenuator or build one out of two resistors.

This is what I would try:

2.2K 10uF
(+) ------/\/\/\--------+--------|(-------- Line
120 |
(-) ------/\/\/\--------+

GND -------------------------------------- Line GND

 

Calpis: So I should tie Speaker (-) to Ground to prevent any chance of damage? Also, I don't understand your diagram.

Would a car audio attenuator like what Retro linked work if I just connected that to my system? Though I still have the option to use those spare speakers if I were to figure out a decent way to connect them.

 

Lol, ASCII art fail Paint is your friend!!!

It's just an attenuator... as it says in the title "speaker to (2 RCA) line level", which is exactly what you want. It also says in the description for car or home use

 

Noooo, you should tie RCA GND to JAMMA GND. The whole point is that (-) goes negative (or positive depending on the game or if wires are crossed), and when it is tied to either the JAMMA GND or the RCA GND (which could be at the same potential as JAMMA GND) current will flow from the most potential to the least potential.

The bottom resistor is 120 ohms, the top is 2.2K, the cap is 10uF.

It's a resistor divider, but the concept is more difficult since since (-) goes negative. So regardless of how high (+) goes and how low (-) goes, there will always be ~20:1 attenuation. This attenuated signal still won't necessarily be suitable for the line input since the speaker polarities can be switched (this may not matter to a speaker), there could be a DC offset, the signal may swing from positive to negative or both rails may mirror each other. There are so many configurations that should be accounted for so the signal is AC coupled which only allows voltage fluctuations to pass. This circuit still wouldn't work correctly if the game board switched (+) and (-) because it wouldn't attenuate 20:1 it'd attenuate 20:19 or so which is useless. I can think of a more complicated circuit that will handle that too, but it requires 6 resistors and is less stable.

Yeah... but chances are it'll cost $10 and just be 4 resistors, 2 dividing each channel by 10, and not accounting for all sorts of crazy arcade implementations.

Yeahhh, was trying to avoid Paint for a 2 resistor diagram. Maybe if I find the time I'll draw something with the graphics tablet.

 

Well see right now the RCA's Ground/Shield connects to JAMMA Speaker (-). The Center connects to Jamma Speaker (+). You're saying I should connect JAMMA GND to the RCA Ground/Shield and NOT Speaker (-)? Or connect GND AND Speaker (-) to RCA Ground?

And this can all basically be negated and just run Speaker - and + to a regular arcade type speaker right?

 

I know, and that's not good! lol

You're correct, connect JAMMA GND to RCA GND and not speaker (-). (-) and any type of GND don't mix.

Yeah you can connect (+) and (-) to any 8 ohm speaker. Most arcades will probably allow 4 ohm speakers too since (I think) cabs often have two speakers in parallel. So if you want:

1 speaker - use 8 ohm or 4 ohm
2 speakers - use 2x 8 ohm in parallel or 2x 4 ohm in series

 

Well I have an old CD player set of speakers that says something about 4 ~ 8 ohm speakers. I used one once to test the sound and it worked. I guess I could wire up a connector to the Supergun as well as the speakers.

As far as right now I should disconnect Speaker (-) from the RCA and have it connected to nothing and connect a Ground Wire (from the PSU or Jamma or doesn't matter?) to the RCA Shield?

 

Yup. I'm not sure how the audio will sound though, possibly really distorted.