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Star Grounding Schematic


Xanthus
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Yeah, wiring is still a way's away, but I decided to throw all my questions out now. Moving back in to Emmanuel tomorrow, so the threads will have time to run down the boards before I'm back online.

Click for pic

I've heard a whole lot of cool things about star grounding, and decided to MSPaint up a schematic right quick. My concerns lie mainly with the ground wires running from the volume and tone pot. Usually, the volume tab is soldered back onto the shell, and a wire is run to the tone. From there, the wire runs down to the ground on the jack. Were I to run a wire from the volume pot to the washer (without bending the tab back in on itself) and a wire from the tone pot to the washer, would I achieve the same effect? I realize that in my limited wiring experience, I could very well have misred the original diagrams entirely.

The tone pot looks a little odd, being connected only by the capacitor. Just looking for a kind soul to tell me whether or not this diagram would work or not.

Also, as an aside: Should I get regular bare wire, or shielded wire for this job?

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Looks fine to me.

As for the shielded versus plain wire. The problem with shielded wire is you have to ground the shield, which can be a major pain and may, if not done properly cause you some grounding problems. If your components aren't too far away (as in a strat/tele style route) i wouldn't bother. Its only in long runs (as in lespaul tone/vol to the pickup selector and back to the jack) that i'd use shielded wire.

S

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Looks good to me. In fact, when using star grounding it is preferred to not bend the tabs back to the pot, but to go directly to the star.

Are you using any copper shielding and so forth? Make sure that the star and other exposed parts of the ground do not touch the shielding material. Wrap in electrical tape.

Greg

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:D Thanks a lot, Sambo and Greg. I've never examined the wirings of my other guitars very closely (probably should, haha), so I had no clue what effect bending the tabs back would have on the circuit.

Yeah, I'll be using some copper shielding, going to cover the cavity, back of the cover, and most likely the pickup cavities too. Is there such a thing as extra precautions? heh.

So unshielded wire it is, then. The cavity is very small, yeah, I wanted to leave as much wood as possible, because surprisingly the guitar is pretty light as is. I'll just remember to do a better route job next time, and make the template the way I want to do it :D

Thanks again, men!

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The shielding material will need to be grounded to the star as well. This is the only time that you really have to think carefully, and the best way to visualize it, IMO, is like this:

Any conductive surface that surrounds your electronics (ie. the shielding material and the pots) should be treated as one "unit".

1. So, you have your shielded cavities, including pickup cavities, all electrically continuous with each other.

2. When you put your pickups in, the wires don't contact the shielding material. The cover and baseplate ideally won't, because they're already connected to the ground in your 4-conductor wire. You don't want to ground at 2 different places.

3. When you put your pots and switches in, they SHOULD contact the shielding material. This will add the pot cases to the "shielding unit" as it were, but the internal electronics aren't actually in contact with these. The pot's 'guts' as it were, will be grounded to star as shown in your diagram.

4. Now you need a wire from anywhere on the shielding material (the back of a pot is fine, if you've confirmed that it's electrically continuous with the shielding material, otherwise, a screw somewhere in the cavity with a wire connected to it works) leading to the star.

5. Make absolutely sure that neither the star nor any of the wires leading to it have bare metal touching the shielding material. Use electrical tape to cover up any exposed wire.

That'll do it.

Greg

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Dumb question, but if the star is connected to the shielding material to ground it, why would it be bad if the exposed star touched the shielding material. The only thing I see it doing is being a redundent connection.

When a shield blocks an electric field from affecting you circuit, currents must flow into and out of the shield. The idea of star grounding is to prevent these currents from getting mixed up with the signal currents and effectively puttting a small hum signal in series with the guitar signal. Star grounding is less important in a guiitar than an amplifier where you have much larger currents from power supplies, etc., but it is still the proper way to do it. For star grounding to be really effective, the separate shielding connecton should continue all the way to the amplifier rather than coming together with the signal at the jack, but it is hard to fight tradition.

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