Oval outline in schematics

[MaximRecoil]

When schematics show a small oval at a wire intersection, what does that mean?

[ChadTower]

It almost looks like the intersecting line is passing through but not touching, which of course doesn't make sense.

[Ken Layton]

It means it's a shielded wire. The oval is the braided shield covering the center conductor.

[ChadTower]

So anything joining that line would have to pass through the shielding?

Is this a conductive shield, like in a coaxial, or just a sheath that prevents interference?

[RayB]

Looks like it means that you connect to the shield only...?

[MaximRecoil]

It means it's a shielded wire. The oval is the braided shield covering the center conductor.

Where do you get shielded wire? I've wired plenty of car stereos and I have never seen shielded wire for anything other than coaxial-type wire such as audio interconnect cables (RCA) are made from.

And if I find shielded wire, I guess I still don't see how to make that circuit. I see the ground wire going up to the sound wire, and then there is that oval. Now I can't imagine that at this point, both the sound wire and the ground wire as bare conductors run through a single shielded insulator...or does it just mean that they run side by side, both with their own separate shielded insulators? or are they just ordinary insulated wires running side by side through a shielded loom or sheath type arrangement?

[Ken Layton]

Shielded wire can be made with any number of conductors inside it. The oval on the diagram merely indicates in simple terms that the braided shield (like a coax cable) covers the entire length of the conductors inside the oval. In most cases it's a single center conductor.

[MaximRecoil]

Shielded wire can be made with any number of conductors inside it. The oval on the diagram merely indicates in simple terms that the braided shield (like a coax cable) covers the entire length of the conductors inside the oval. In most cases it's a single center conductor.

How necessary is this shielded wire going to the audio amplifiers? Could I just use coax cables to go from the board's postive and ground pinouts to the audio amps and call it good? If I did that, wouldn't I have to connect the ground to the outer braid and the positive to the center conductor?

I wish I had a real Punch-Out wiring harness, or at least one to look at.

Edit: Could I solder a female RCA pigtail to the "sound" and "ground" on the board's pinouts (onto the card edge connector actually) and another onto the inputs on the amp and then simply run a shielded RCA cable between the two?

[Dave_K.]

Looks like it means that you connect to the shield only...?

Yes if you notice those oval connections go to ground...so its just grounding the sheilding only.

[MaximRecoil]

Looks like it means that you connect to the shield only...?

Yes if you notice those oval connections go to ground...so its just grounding the sheilding only.

That doesn't make any sense. Where do you get shielded wire that would allow you to connect a ground wire to the shield? Shielding is generally wraps of aluminum foil and sometimes polyester tape in addition. How do you connect a ground wire to foil or tape?

[JCL]

Looks like it means that you connect to the shield only...?

Yes if you notice those oval connections go to ground...so its just grounding the sheilding only.

That doesn't make any sense. Where do you get shielded wire that would allow you to connect a ground wire to the shield? Shielding is generally wraps of aluminum foil and sometimes polyester tape in addition. How do you connect a ground wire to foil or tape?

Solder to it or use a crimp on connector designed to work with that type of wire. For example, crimp on connectors are often used for TV cable coax, a type of shielded wire. A solder joint to the foil is pretty weak, so be sure to leave some slack or use some sort of strain relief.

[MaximRecoil]

Solder to it or use a crimp on connector designed to work with that type of wire. For example, crimp on connectors are often used for TV cable coax, a type of shielded wire. A solder joint to the foil is pretty weak, so be sure to leave some slack or use some sort of strain relief.

Right, I was thinking the same thing regarding the crimp on connector when I mentioned the idea of soldering a female RCA pigtail to both parts and running a standard RCA audio interconnect cable (which is the same idea as TV cable coax) between them. The connectors for coax, whether they are RCA or F-Type, connect to the center conductor of the coax cable on their center pin and the outer rim connects to the outer conductor (braided wire), which in turn is contacting the foil shielding. In fact, doesn't the braided wire itself contribute to the shielding, in addition to the foil?

So I think the best way to do it would be to get a couple of female RCA pigtails, which is just a female RCA connector with two ordinary wires attached, one connected to the center pin and the other connected to the outer rim. With one of these pigtails, I'll connect the outer rim wire to ground on the ground pinout of the game board, and the other I'll connect to positive ("sound"). With the second pigtail, I'll connect it to the ground and "sound" points on the amplifier in the same fashion. Then I can take any RCA cable that I have kicking around and connect between the two pigtails. This is exactly how any other audio setup works to get the low level signal from the preamp to the amp, so it ought to be good here as well. Then from the amp to the speakers, you just run ordinary "speaker wire".

Does this sound about right to everyone?

[RayB]

Foil?

Tear apart a pair of headphones, and look at the wire that goes to each ear piece. You'll have a copper core and then there is stranded wire that wraps around the outside (ground).

[MaximRecoil]

Foil?

Tear apart a pair of headphones, and look at the wire that goes to each ear piece. You'll have a copper core and then there is stranded wire that wraps around the outside (ground).

Coax has braided wire on the outside which I guess would contribute to the shielding, as ground connects to this. But, it also has aluminum foil shielding under the braided wire, the better stuff does anyway.

When I questioned connecting ground to a shield, I wasn't considering the outer braided sourrounding wire as part of the shielding, but since it is (I think), then there shouldn't be any problems. I'll just use RCA connectors to make it clean and neat.

I'm not sure why headphones would use shielded wire going to the ear pieces (speakers) though, I would expect normal speaker wire for that. Normally in audio setups, the shielded wire (such as as normal "RCA cables") is only used for a connection between the source low level audio signal and the amplifier. Sometimes "twisted pair" speaker wire is used to go from the amp to the speakers which adds a bit of shielding, at the expense of increased impedance.

[SirPoonga]

Looks like it means that you connect to the shield only...?

Yes if you notice those oval connections go to ground...so its just grounding the sheilding only.

That doesn't make any sense. Where do you get shielded wire that would allow you to connect a ground wire to the shield? Shielding is generally wraps of aluminum foil and sometimes polyester tape in addition. How do you connect a ground wire to foil or tape?

Solder to it or use a crimp on connector designed to work with that type of wire. For example, crimp on connectors are often used for TV cable coax, a type of shielded wire. A solder joint to the foil is pretty weak, so be sure to leave some slack or use some sort of strain relief.

Yep, if you have ever taken apart a gibson electric guitar or bass you will see pots are gorunded to the shielding of the sound wire.  And at the jack the shielding is connected to the ground of the jack.   Most of the componants, depending on how fancy the circuit is, are soldered directly to the shielding.  Like the volume and tone pot, the sound wire is routed pass them and the shielding is soldered directly to the pot's casing.  But, on the fancier circuits (like ones with active pickups that use a 9v battery) a wire from the componant may be running to the shielding.  This way everything gets grounded to the amp gorund when the guitar is plugged in and the sound wire is shielded from interference.

Which reminds me, I need to find some shielded wire and modify my squier pbass, it has nasty interference sometimes.

[MaximRecoil]

This is what I plan to do:

[SirPoonga]

That looks good.  As long as the cable's ground is the shielding of the cable.

[JCL]

Which reminds me, I need to find some shielded wire and modify my squier pbass, it has nasty interference sometimes.

I've seen a  great site about shielding a strat, might have some tips for your bass: http://www.guitarnuts.com/index.php.

Some day I should fixup my cheapass (did that get by the autocensor?) squier strats.

[MaximRecoil]

This is what I plan to do:

This setup worked really well, and has the added benefit of a standard audio hookup that could be used with any home stereo, PC or car audio amp, rather than just being limited to the amp on the Sanyo monitors. When I ran a long set of RCA cables into the mic jack on my PC to record some sounds off the machine, the game sounded awesome through through my Logitech PC speakers, much better than through the crappy (or just old and worn) original amps/speakers that are in the cabinet now. If I were to actually install a different sound system in the cab, I would need two amps; one per speaker, because the dual amp/dual mono setup in that cab uses one amp for the announcer's voice and a few other effects and the other amp for the music and the rest of the game sounds; although you can use a Y adapter to get all of the sounds through one amp in a summed mono setup; which is what I did when I ran it to my PC, though you would lose the effect of having the announcer's voice coming from one side of the cab and the other sounds coming from the other side of the cab.