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F3 Line level sound

playthatbeat

playthatbeat

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I run an amp for my arcade boards' sound, feeding a Sub and 2 6x9 2 ways. The amp is fed from a small 12 channel mixer. I have 6 boards on a switcher in one cabinet. Some boards have LINE level audio out, so there are no problems.

Some require a pad to reduce speaker level to LINE level. The F3 is one of these. The S header is a direct output to speakers, not line level, so, not wanting to blow the crap out of the channel, i made a pad for each leg and connected it into my mixer. Games would boot fine, but as soon as the sound started, it would crash and go into a boot loop.

Frustrated, I resorted to tapping the Jamma sound (mono) from the jamma extender, which is also speaker level, padding it, and using that. I found the problem was reduced, the sound would work fine, but games would crash when the audio level went up (like a big explosion) during a game!

The solution was to lift the - of the speaker feed from the input to the mixer after the pad circuit. I can only assume the audio GND from the F3 is connected to the Jamma GND anyway, and a spike in audio level would cause chaos, and a crash. So, now i have Line level audio, from the jamma out of the F3, but after padding it to line level, i'm only connecting the + to the mixer Line IN - all i did was snip the - inside the jack that plugs into the mixer.

I have not had to do this with the other games i padded the speaker output from, they all connect to the mixer without issues thru the same basic circuit (below), so there is something different going on with the F3 audio outs. Still running it in MONO, i'll try the S header for stereo/2 channel again some other time..
 

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audio ground is not always connected to the digital ground. It's actually "audio -" NOT a true ground.

I don't know about F3 but I do know in later Taito PCBs (such as G-Net and and Taito Wolf system), they use the audio negative to produce an inverted wave form for one channel with the positive to produce a normal wave form for the other channel in order to allow for stereo output on the JAMMA edge.

this is a clever way to do it as a stereo cab that uses the digital ground will be cable to play stereo, but a mono cab that has the speakers run directly to this will play both channels out of the same speaker.

the problem is that when you do what you've done and tied the "audio ground" to the digital ground you're actually shorting out the audio circuit. it's not actually a ground it's "audio -" in some cases it's indeed just a ground reference but in other cases it's an inverted audio wave form.

I'm honestly surprised the worst that has happened is your game crashing as this could very easily cause you to let the black magic smoke out of your PCB/burn up traces and ruin your PCB..

Audio ground and video ground are on their own pins for a reason... they should be isolated from the normal digital ground. While they are tied to ground in some cases you should never assume that's ok at the harness level.
 
Well, to be clear, i'm taking the audio from the Jamma loom straight from the F3, which should be expecting to see a mono speaker, but i'll check the game/board menus now and see if it is doing it's magic trick to generate stereo from 1 pair, as that would explain alot.

Interesting.. Thought the S header must be more then the game manuals imply - they show the header as being SPEAKER outs only, but they for sure do not behave like that on the game i'm playing (Darius). Could be a game specific state? i only really looked at the Puzzle Bobble 3 manual, which says S is 'speakers'.. well, i'm going to keep away from the S header in that case, i'll leave it as just a pad on the jamma speaker out for now.. I guess i could add a speaker/speakers for just the F3 alone if it starts to freak out again.

This audio trickery could also explain why My G-net has phase issues on some games, i tapped that from the audio header (stereo mode selected), but did not need a pad as the G-net has a handy volume pot, so it's not as hot as the F3 was. It's producing a stereo field, and it matches the screen positions of events, but there are a few effects that sound out of phase or weird - i put this down to the 90's attempts at 'virtual 3d sound' which was all the rage for a while.
 
the g-net should have a switch for mono/stereo. I'd suspect the F3 has one as well.

the Taito wolf hardware has an amplified stereo header too, so it wouldn't surprise me if they did the same on the F3.

I'd suspect the "clever" stereo wiring setup was in support of their own cabs. the Egret 29's speaker wiring is designed explicitly to handle it as you can see in the wiring diagram I colored here:
Taito Egret 29 Restoration
 
The F3 has a 4 pin header on the PCB for stereo out
 
PascalP said:
The F3 has a 4 pin header on the PCB for stereo out
Click to expand...
We know that. the problem is that
1. it's AMPLIFIED
and
2. the JAMMA Edge may also support stereo through the use of "audio-" pin being used as an inverted channel.
 
Ah ok, the way I read the thread is that you wanted you tap into the pcb somehow for stereo sound.
If you don't want amplified stereo or don't want to use a line level converter, than yes, you would need to look into other options.

Good luck ;)
 
Just had a good burn there on Darius.. no issues using a pad on the Jamma speaker out to the sound system.. I suspect it should in fact produce stereo though, as the soundtrack is put together far too well to *not* be in stereo in fairness - layers of streamed PCM music and at least 4 channels of SFX. There is nothing in the F3 service menu relating to format of audio. You can test the music and each of the SFX is all.

Does not seem to be a manual anywhere online for Darius on F3 (i didn't look THAT hard but..) which might be a pointer as to how the sound on the jamma connector is configured for the game, i see that a couple of the other F3 manuals out there have the basic diagrams that the F3 motherboard manual has, but some include more detail on headers.

But, for me anyway, Tapping the S header to derive stereo LINE is not working predictably/at all.
 
looking at the puzzle bobble 4 manual provides some insight:
https://www.arcade-museum.com/manuals-videogames/P/Puzzle Bobble 4.pdf

the S connector is pinned like this:
1. Right Speaker (+)
2. Left Speaker (-)
3. Right Speaker (-)
4. Left Speaker (+)

They suggest if looking for mono you wire the speaker to pins 1 and 2.
ALSO the L and 10 pins on the JAMMA edge are labeled as "Speaker (-)" and "Speaker (+)" which seems to imply that these may be simply wired to pins 1 and 2 on the S connector, which would also be the same "clever" stereo JAMMA wiring that g-net and Taito Wolf uses.

You could easily verify this with a multimeter.

They also list the JAMMA edge as having "Audio GND" and "Audio (+)" on pins M and 11 respectively, which may be mono line level out. the extended JAMMA spec does allow for this though it's rare that they're actually used.
 
I missed that totally about Pin 11 & M! Just went for the usual Pin 10 etc as they were wired on my harness, pretty sure 11 and M are not.. OK, this makes sense., I'll investigate pins 11/M and see what they are doing.
 
Hy guys.

I want to take the audio from the s connector off the taito f3 mainboard.
Can sonebody please tell me what I need to buy in order to make that possible.
As far as i see there is need of a line out converter.

Right?

I just want to go with the audio directly from there to the Scart Adapter which is connected to my TV.
Thanks.
 
Correct. S-Connector is not line level, it's amplified, so it will need to be attenuated. if you search on amazon for "line out converter" there are dozens of devices that can do this.
 
Ok i try to look.

I hope there is something like that in Germany.

But it's not digital to analog needed?
 
There's an image in another thread which shows where to solder to get access to the unamplified sound, it's pretty easy. I'm still not entirely certain which is L and which is R though (because the first game I tried seemed to have them flipped from all other games).

Sorry, don't have time to hunt for the other thread right now :/
 
Thanks.

You mean they pick it up at the jamma connector ?
 
Thanks

I will try this one.

I guess I need a cable that has ground for both auto channels on one wire
 
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