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Yesterday I gave my Aria D'Aquisto to a guitar tech to replace the Bartolini floating humbucker with a Aaron Armstrong Benedetto-style S-6, designed for picking up a signal from acoustic strings. The tech just phoned saying there was a hum, and the strings were not earthed. This is beyond my ken, so your opinions are welcome. I've to go and collect the guitar this afternoon. He said I should play it at home, see what I think, and if I wanted, he would find some way of earthing the strings. What do you think?
Last edited by Rob MacKillop; 04-21-2017 at 05:54 AM.
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04-21-2017 05:47 AM
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Hi Rob
I would get him to earth the strings, otherwise they act as an aerial for any sources of hum (e.g. fluorescent lighting).
Is your tailpiece like the one below, including the brass strip through which the strings pass ?
If so there should be an earth wire that passes up the back of the tailpiece from inside the guitar to make contact with the brass strip. This can easily become disconnected at some point from the wiring harness during work on the guitar - e.g. replacing a pickup. It maybe that your guitar tech did this unwittingly, or it could have happened before you acquired the guitar - or maybe it was never installed in the first place !
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Rob, did it hum with the old pup? If not the ground to the jack may have broken? Where is the jack? On the rim, end pin, or PG?
In any event, it should be easy enough to re-install a ground wire.
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First off I'm going to assume it's an Aria solo ( beautiful guitar btw).
Originally Posted by Rob MacKillop
The principle is that all the metal parts on the guitar (pots, jack, pick ups, strings) need to be grounded to a common point. Think of it as a sink which sucks in hum and background noises. The internals(pots, jack etc.) are connected via a ground wire. Strings on the other hand ...
Usually under the wooden tailpiece, archtops have a metal piece where the balls of the strings are lodged... Electrically Connecting all the 6 strings together. This metal piece extends to the screw that holds the lower end of your strap. Internal this is connected to the common point where the other metal components are grounded.
The ball end of the Aria's seem to be connected to a wooden tail piece with no metal underneath therefore unable to connect to the internal common point.
He's a guide that shows you how to mod your guitar.
www.guitarrasjaen.comGroundingTailpiece_EN.pdf
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It's a completely wooden bridge.
The Bartolini was installed before I bought the guitar. I never noticed a hum, but I only tried it home, not on a gig.
A student of mine installed Schatten thumb wheels.
The tech today said whoever did that put them on the wrong way round (or something like that). So, it was in a bit of a mess.
The solution by Jaen Guitarras for grounding the strings looks an expensive option. The tech today said he could come up with a different solution if I wanted. Sounds from the comments above that I need to get this all sorted out. Thanks for the comments!
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Yes, usually it is as simple as a wire going from the earth of the pickup or a potentiometer or anything that is earthed really to the tailpiece. With a wooden tailpiece there will have to be a bit more ingenuity used! I find it hard to believe that a guitar that was sold with a pickup didn't have string earthing though. Perhaps there is some metal under the tailpiece and a wire has come loose.
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Well, I've told him to go ahead and find a way to earth the strings without anything being visible. If there is not a loose wire under the tailpiece, he will make a brass plate where the strings enter the tailpiece, as in post #2 above, and do all the wiring that is necessary.
This is why my next guitar will be all acoustic, and no pickup!
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I had that problem when installing a Benedetto tailpiece on my Guild - my tech solution was to shield the tailpiece with an invisible metal layer. Meanwhile, I got an original Guild metal harp tailpiece that he covered in ebony, I can send you my Benedetto tailpiece if you want to use it or just to copy the idea, I have no use for it.
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I've a similar issue with my '81 Epiphone. There's a ground running to the treble bridge insert in the body, but a previous owner installed a bridge using nylon saddles. Ergo, no ground to the strings.
When I completely rewire it next month, I'm installing a redundant ground to the tailpiece. Then the strings will be grounded regardless of the bridge/saddles used.
Good luck sorting yours out.
B.
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Shielding is needed when there is no string grounding being used. When the strings are grounded the guitar is slightly less safe. The point of grounding versus shielding has to do with safety. If your guitar is shielded well enough that a string ground is not needed to keep it quiet , you are a little more safe from accidental shocks. The danger in string grounding lies in reversed grounds. It is very rare that someone is shocked by reversed polarity of stage equipment but it certainly has been known to happen. You may want to check your shielding first before grounding your strings. The simple circuit on most achtops is easy to shield in most cases. Sometimes string grounding is the only way to effectively quiet a noisy circuit.
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This is the same answer Bob Benedetto gave me. Thought he was exagerating but I have tested time and again.. it works. Originally Posted by Matt Cushman
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Originally Posted by jorgemg1984
I'm okay for now, Jorge, but I really appreciate your offer!
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Thanks for all the comments.
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Grounding the strings is safer if a high voltage rated small uF capacitor is wired between the ground and the strings. That should block noise from high frequencies and block AC.
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When there is a string ground (earth), the guitar is grounded to the guitarist. The guitarist's body acts as a capacitor. If you stand in bare feet on a concrete floor, plug your string-grounded guitar in to a live amp and hold the neck, you may be able to feel the current.
The fundamental problem with guitar hum is that the circuit to the amplifier is really not that well designed. If it were properly designed, there would be no need for a string ground in any guitar and there's be little or no hum even with single coils. But we guitarists are stuck in the 1950s in so many ways.
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While this is true, caps can short which is like having a solid wire run the bridge to ground. Originally Posted by Matt Cushman
I prefer to use a resistor 220K or higher as resistors will tend to go up in value when exposed to a heavy load or open up altogether. It won't be as quiet as grounding the guitar to your body but I find this is mainly a problem when a gain device is used.
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One can actually test the AC current phenomena. You take 2 devices with non-polarized plugs and plug them into an AC outlet. You can take an AC voltmeter and check the metal chassis (ground) between both units. Measure the AC from both units and see what you get. Now reverse One of the plugs and read it again. Many times you'll read 117V (US) in one direction and OV with a plug flipped. This is why they went to polarized plugs and the 3 plug design.
I've had incidents years ago where I was holding my guitar and got a scary shock when my lips touched the mic ! Ouch! Makes you see stars. Could be deadly if you're full of sweat. Most of my guitars have a resistor to ground for that reason. I'm not going to trust a venue to have 100% safe AC wiring.
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A wire from the output jack to the tail , and then some conductive paint from underneath the string slots to the brass part of the tail Electrically Conductive Silver Paint | Maplin Originally Posted by jorgemg1984
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Or if you want to do it cheap 1 part powdered graphite, 1 part nail polish remover and 1 part clear nailpolish (cheapest dollar store stuff you can find.. no need for Maybelline) Originally Posted by fws6
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Easier than paint is conductive tape. You can buy it in rolls of various widths, and you just apply it like any other tape. That's what I would use.
Put "conductive tape" into your favorite search engine, and you'll find more information than you wanted to know.
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