megi
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Post by megi on Feb 13, 2012 11:10:43 GMT -5
Continuing my "dumb question" line of threads ;D, I have some more for the forum, in relation to the metal covers often used with humbucking pickups and the neck pickup on a tele, for example.
1) What effects, if any, do they have on the tone produced, when fitted as normally with a connection to ground? What type of noise do they help to reduce i.e. mains hum, or is it a different type of interference?
2) If the pickup cover is fitted, but not grounded, does it influence the tone in any way, or is it just as if the cover is not there at all?
Thanks guys, interested to hear the answers to this one.
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Post by newey on Feb 13, 2012 11:43:09 GMT -5
I'll tackle your second question first, and leave the first to someone who has done an A/B comparison with cover on/off.
But, even if not grounded, the cover will affect the tone. If not grounded, it won't help with the noise end of things.
A metal cover, even if not grounded, will alter the magnetic field of the pickup's magnets to some degree. And, the sound of the pickup is dependent on the size, strength, and other features of the magnetic field. So, even an ungrounded cover can, at least theoretically, alter the tone of a pickup.
Whether it does so in practice or not depends on many variables, including the ear of the listener in question.
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megi
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Post by megi on Feb 13, 2012 11:57:48 GMT -5
Cheers newey, that makes sense. I suppose a further question I have is, is there any difference in the effect on tone between a grounded and an un-grounded pickup cover, besides the obvious shielding from interference that a grounded cover gives?
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Post by ashcatlt on Feb 13, 2012 13:53:29 GMT -5
Cheers newey, that makes sense. I suppose a further question I have is, is there any difference in the effect on tone between a grounded and an un-grounded pickup cover, besides the obvious shielding from interference that a grounded cover gives? Theoretically yes. The metal cover separated from the coils by an air gap acts like a capacitor. That capacitor doesn't do anything with only one "end" (the coil end) connected. When you connect that other "end" to ground it has the same effect as any other smallish cap you'd put parallel to the pickup. It acts as a low pass filter. In practice it's a pretty subtle damping of the highest treble harmonics.
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Post by JohnH on Feb 14, 2012 4:15:14 GMT -5
I had a chrome cover on the neck pickup of my LP, but not on the bridge. I always found the bridge had heaps of sparkle, and the neck was a bit too mellow - beyond what you would expect just due to its position. So a few months ago I took the cover off - and it has significantly more edge now, and a bit more noise, but I much prefer it that way
John
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megi
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Post by megi on Feb 14, 2012 5:17:11 GMT -5
Cheers newey, that makes sense. I suppose a further question I have is, is there any difference in the effect on tone between a grounded and an un-grounded pickup cover, besides the obvious shielding from interference that a grounded cover gives? Theoretically yes. The metal cover separated from the coils by an air gap acts like a capacitor. That capacitor doesn't do anything with only one "end" (the coil end) connected. When you connect that other "end" to ground it has the same effect as any other smallish cap you'd put parallel to the pickup. It acts as a low pass filter. In practice it's a pretty subtle damping of the highest treble harmonics. Interesting... well I wouldn't have thought of that, but again it makes perfect sense, thank you for that informative answer!
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megi
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Post by megi on Feb 14, 2012 5:26:08 GMT -5
I had a chrome cover on the neck pickup of my LP, but not on the bridge. I always found the bridge had heaps of sparkle, and the neck was a bit too mellow - beyond what you would expect just due to its position. So a few months ago I took the cover off - and it has significantly more edge now, and a bit more noise, but I much prefer it that way John Thanks John, it's good to have some direct evidence-based feedback re the metal covers. I have 2 guitars with humbuckers and no covers, and I'm fine with the noise issue, and like the sound, so I don't suppose I will be fitting covers to those any time soon given what you're saying - I like a bit of edge too. I do have a jazz guitar which has a humbucker with metal cover so I could test that sans cover - it does seem a little lacklustre sounding to me sometimes - although that could be down to the operator of course... I guess what put the subject of pickup covers in my head is that I'm fitting a new set of pickups to my tele at the moment, and although the neck pickup has a cover, it is easily removable, and not connected to ground yet either, so I have the option to experiment if I want.
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Post by reTrEaD on Feb 14, 2012 10:10:01 GMT -5
2) If the pickup cover is fitted, but not grounded, does it influence the tone in any way, or is it just as if the cover is not there at all? Having the cover in place, but not grounded, might be a difficult thing to accomplish. In addition to the solder that is traditionally used to hold the cover to the baseplate, the holes allowing the pole screws to protrude from the cover are often small. Preventing the cover from touching any of the screws might be tricky. In my opinion, there is more to the story than the capacitive effects mentioned by Ash. The eddy currents in the cover would be different with the cover grounded vs not grounded. These will affect how much energy makes it through the cover and probably how the path changes. Electromagnetic shielding is part science and part black arts. I think anyone who claims to fully understand it is either a bit too full of himself or truly a genius. I think the best you can hope for here, is more of what you've already seen. Speculation about what might happen, based on the limited knowledge and experience each of us has. I vaguely recall John mentioning (on a different thread) that the slug coil of a covered HB seemed wimpy compared to the screw coil. And that removing the cover "opened up" the sound. I would GUESS this to be true because the cover changes the focus of the stationary field of the magnet (via the slug) on the string. With the magnetized area of the string being more diffused (wider and less polarized), this would decrease the output. The above is of course, just speculation.
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