wohzah Posted June 3, 2008 Report Share Posted June 3, 2008 What is the rule of thumb for pickup covers? What is the max thickness? What are the material restrictions? Thanks, I am speaking in reference to single coils as in covering over the magnets. Quote Link to comment Share on other sites More sharing options...
foil1more Posted July 22, 2008 Report Share Posted July 22, 2008 no rule. the magnet field of the pickups shouldn't be altered by a cover of any kind. As long as the cover doesn't interfere with the strings you're fine. (the only thing that should effect the magnetic field are other magnets). Quote Link to comment Share on other sites More sharing options...
dpm99 Posted July 23, 2008 Report Share Posted July 23, 2008 Since someone drug this to the top, let me re-ask the question in a different way. For my project, I was planning to use a pair of Gibson pickups from an old Explorer (496R/500T). It was my understanding that they should remain uncovered, because they are ceramic pickups. Not true? Will covers effect the tone? (Even if an opinion can be called tone "Voodoo" I'd be curious to hear. I'm a bit of a believer in that weird religion.) Thanks, -Dave Quote Link to comment Share on other sites More sharing options...
bluesy Posted July 23, 2008 Report Share Posted July 23, 2008 no rule. the magnet field of the pickups shouldn't be altered by a cover of any kind. As long as the cover doesn't interfere with the strings you're fine. (the only thing that should effect the magnetic field are other magnets). I believe some metals can interfere with a magnetic field. A metal known as mu-metal was used in oscilloscopes to shield the beam from magnetic deflection. There may be other related metal alloys as well. here's a wikipedia reference http://en.wikipedia.org/wiki/Mu-metal that said, it's not likely that someone will make pickup covers out of it Quote Link to comment Share on other sites More sharing options...
dpm99 Posted July 23, 2008 Report Share Posted July 23, 2008 Bluesy, stop posting the same minute I post! Quote Link to comment Share on other sites More sharing options...
bluesy Posted July 23, 2008 Report Share Posted July 23, 2008 Bluesy, stop posting the same minute I post! Sorry Quote Link to comment Share on other sites More sharing options...
psw Posted July 23, 2008 Report Share Posted July 23, 2008 Hi...some misunderstandings here. Any magnetic metal will have dramatic and disastrous effects on a pickups function. Gibson and like covers are made of plated brass and are as such non-magnetic but will conduct electricity. The idea is that these covers were to drain stray radio frequency interference RFI to ground, but in reality they have little effect as the humbucking effect largely deals with that. The other effect is induced eddy currents in conductive (though non-magnetic covers). These though are very small and have little real effect on tone but perhaps some. The real benefit is that without a cover the pickup can be adjusted even closer to the strings comparatively resulting in a much higher output. So a magnetic metal is definitely a big no-no. Mu metal is often used because it is highly magnetic and so a more effective shield. This exactly what you don't want however in a pickup that needs the magnetic field, not blocking of it! So the myth of the covers is most down to the perception that it creates a hotter signal without them with little if any difference in noise by being able to be adjusted closer. There may be some effect of eddy currents but it is not particularly noticeable. Mainly it is done for appearance. Zebra coils were discovered because traditional vintage pickups often had mixed bobbins by complete accident and so some voodoo became associated with these PAF types and this lack of quality control (not important as they were covered) indicated their vintage. Not being aware of this at the time and the significance it would eventually would have, gibson tightened quality control to typically all black bobbins. Because of this these zebra black and cream become desirable and were later intentionally made by replacement guys to cash in on this myth and the look of exposed coils. Single coils are rarely metal covered, perhaps there is a reason for this although some are like some P-90 dog ears. It is possible that eddy current effects might be more noticeable in a single coil design. If so, the effect would be to roll off the treble a little I suspect. If covering a pickup it must be non-magnetic like brass or possibly aluminium and very thin and earthed. As soldering to aluminium or plating can not really be done, brass is traditional. In sustainers I have noticed that the high currents in the driver coil (like a reverse pickup) are seriously adversely effected by covers and so are to avoided completely in practice. However, these are different devices that highlight such things as eddy currents and should not adversely effect the operation of a pickup. OK...so I hope that helps or if I have it wrong, let me know... pete Quote Link to comment Share on other sites More sharing options...
dpm99 Posted July 23, 2008 Report Share Posted July 23, 2008 Cool! So I get to have pickup covers after all. Thanks Pete! Quote Link to comment Share on other sites More sharing options...
WezV Posted July 23, 2008 Report Share Posted July 23, 2008 there is an audible difference between humbuckers with and without covers, its not all to do with the extra height adjustment... although i will admit the effect is very slight and you can get more effect on your sound through height adjustment, but generally there is almost a bit more pressence without the cover. this can be compensated for with a slight change in the wind when making the pickup but most manufacturers dont bother. its not an issue really as both sound good but if you had a covered and uncovered version of the same pickup from someone like dimarzio or gibson they would sound slightly different because of the cover. not better or worse, just different. if you did the same with a decent handwound set of pickups from a custom builder i would expect them to sound the same, i know the ones i get from BKP do! having said all that, i would still say choice of covers is an aesthetic choice more than anything else if you are covering pickups with plastic or wood you just need to be aware of how close you want to get the coil to the string. if its a pickup with magnetic polepieces it will generally be left further away from the strings and can have a thicker cover. if its a magnet on the base it can usually be adjusted closer to the strings so you want the cover thinner. generally i wouldnt go over 1/8" thickness as that should be enough for stability with delicate woods but still thin enough to give you almost full adjustment Quote Link to comment Share on other sites More sharing options...
bluesy Posted July 23, 2008 Report Share Posted July 23, 2008 there is an audible difference between humbuckers with and without covers, its not all to do with the extra height adjustment... although i will admit the effect is very slight and you can get more effect on your sound through height adjustment, but generally there is almost a bit more pressence without the cover. ... if you are covering pickups with plastic or wood you just need to be aware of how close you want to get the coil to the string. if its a pickup with magnetic polepieces it will generally be left further away from the strings and can have a thicker cover. if its a magnet on the base it can usually be adjusted closer to the strings so you want the cover thinner. Most pickups have SOME microphonics, and a cover would probably alter that part of the sound. Also, if you like to try to get very close to strings with the pickups, the magnetic pull will cause the strings to vibrate in a less circular way, more of an ellipse. This will change the harmonics (along with the obvious sound level change). Quote Link to comment Share on other sites More sharing options...
dpm99 Posted July 23, 2008 Report Share Posted July 23, 2008 Most pickups have SOME microphonics, and a cover would probably alter that part of the sound. Also, if you like to try to get very close to strings with the pickups, the magnetic pull will cause the strings to vibrate in a less circular way, more of an ellipse. This will change the harmonics (along with the obvious sound level change). Is it kind of like putting a wind shield over a microphone? Quote Link to comment Share on other sites More sharing options...
psw Posted July 23, 2008 Report Share Posted July 23, 2008 Most pickups have SOME microphonics, and a cover would probably alter that part of the sound. Also, if you like to try to get very close to strings with the pickups, the magnetic pull will cause the strings to vibrate in a less circular way, more of an ellipse. This will change the harmonics (along with the obvious sound level change). Ahhh...I forgot about microphonics... some covers will cause microphonics and give the sound a slight metalic ring. Some makers will set the pickup into a metal cover with wax. I took apart a new neck tele SCN pickup recently and removed the wax. It's a great sounding pickup BTW but if I take it apart again I will put the wax back as there is a very high ring on it now (not so smooth) that I don't like so much. pete Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted July 23, 2008 Report Share Posted July 23, 2008 One of the first times I have any disagreements at all with Pete… Gibson and like covers are made of plated brass and are as such non-magnetic but will conduct electricity. Yes and no. Some are made of plated brass and some are made of nickel/silver. I have not A/B-ed the different materials but among pickup winders the nickel/silver versions are highly preferable compared to the brass versions as the nickel/silver alloy doesn’t produce as strong eddy currents. More on that later. The other effect is induced eddy currents in conductive (though non-magnetic covers). These though are very small and have little real effect on tone but perhaps some. It is indeed a fact that eddy currents are produced in all metal parts of a pickup. But I think Pete is underestimating the effect of them. They seriously dulls the tone of a pickup as they produce new magnetic fields that counters the current in the coil that the more “normal” electric generation that takes place in a pickup. The real benefit is that without a cover the pickup can be adjusted even closer to the strings comparatively resulting in a much higher output. Can’t really see how a pickup can be adjusted closer to the strings without a cover as the screws almost always protrude through the holes in the cover and thus are the thing limiting rising the pickups, not the cover. the effect would be to roll off the treble a little I suspect Regardless of if the pickup is a single coil or a HB that is the same effect. A metal cover will roll of treble. Actually it all started when Jeff Beck wanted more treble out of his LP. He tried removing the covers and found that it gave him more bite. And as guitarists always run with the pack (or their heroes) it spread and is now common practice. Metallic covers are used on some P90 as mentioned but also on Tele neck pickups, Burns Trisonic pickups and lipstick pickups. None of those would sound as we expect them to do without the metal cover. And finally the covers change (increase) the inductance of the pickup. Higher inductance generally means a “muddy” sound from the pickup. EDIT: I actually have a set of newly winded pickups waiting for the guitar to be finished. I got curious and measured the inductance (@250Hz) with and w/o the covers. The covers actually lowered the inductance some. But I cannot really see how adding covers would decrease the inductanse. But if it actually does that, it might actually be that factor that, when removing the covers, produces a better bite/more treble. Hmmm... I was surprised by that last part. Quote Link to comment Share on other sites More sharing options...
bluesy Posted July 23, 2008 Report Share Posted July 23, 2008 Is it kind of like putting a wind shield over a microphone? or it might lend resonances to the setup. For example a wooden or metallic cover might ring at a particular frequency, or the cavity formed by the cover and the pickup hole might resonate at another. Quote Link to comment Share on other sites More sharing options...
kpcrash Posted July 23, 2008 Report Share Posted July 23, 2008 so... hypothetically - what effect might be derived by a non-magnetic, fibrous mesh? Would resonance become an overwhelming factor? This is purely curiosity. Quote Link to comment Share on other sites More sharing options...
bluesy Posted July 23, 2008 Report Share Posted July 23, 2008 so... hypothetically - what effect might be derived by a non-magnetic, fibrous mesh? Would resonance become an overwhelming factor? This is purely curiosity. I would imagine you would be approaching the same sound as no covers. Because it's a mesh, then there's no enclosed cavity to resonate, and if it's a light stiff material, intuitively I would expect the cover itself to "ring", if at all, at a frequency that's too high to be reproduced by the pickup. Quote Link to comment Share on other sites More sharing options...
kpcrash Posted July 23, 2008 Report Share Posted July 23, 2008 excellent point - was just thinking that a "screen" type cover may provide the best of both worlds - or something completely different, in the way that a metallic, non-magnetic screen could alter the magnetic field interrupted by striking the string. Anyway - I'll stop being so geeky. Thanks! Quote Link to comment Share on other sites More sharing options...
psw Posted July 24, 2008 Report Share Posted July 24, 2008 One of the first times I have any disagreements at all with Pete… Hence the disclaimer... OK...so I hope that helps or if I have it wrong, let me know... This thread was going so well...hahaha Actually, mine was mostly from guess work and from taking covers off pickups, etc. The bulk of what I said is probably true but yours is a more informed position and you can back it up with measurements like induction...pity it didn't follow the theory quite so well. I am a big JB fan but I have not heard that story...well done, another reason to love the guy! The art of pickups can be fairly subtle and the effect of covers can vary and in large part it is aesthetic. Technically we should see differences but the currents flowing in a pickup are pretty small (compared to a sustainer coil where all such effects can be dramatic) so although magnetic fields may be induced by eddy currents in the metal covers in an HB the sound difference is subtle to my ears. You may be right about the height adjustment to, but I swear that I can get a tiny bit more height on my LP when I got the covers off, about the thickness of the air space and the cover on the slug pole...but again it is slight. Of course, I am not a pickup builder so, I bow to more experience. Some may have more impact and be integral to the design. I am loving my new tele with original full range HB in the bridge and new SCN neck pickup. I notice that height adjustment can have a dramatic impact on tone and especially on the combined pickup. I think the covers are important to both of these underestimated fender designs to their distinctive tone. I am going through a bunch of wiring options at the moment and have found that with this guitar you can get a great 'clucky" sound with the pickups out of phase and that this sound can be varied dramatically by pickup height. It does not have a lot of power so my next mod is likely an active circuit...any tips appreciated. Once I have things settled down on it I will be starting a thread and maybe some sound of these interesting pickups. The fender full range seth lover design for fender is really distinctive and extra large...I am told the pickup is worth more than the actual guitar on ebay such is its current mythic status. The fender FRHB is much larger than a normal HB with wide thinner bobbins and exotic oversized magnet screw poles, I have a feeling that the cover contributes quite a bit to the sound but I haven't had the heart to open it up and from picks I have seen there is a lot of wax in there. Good thread though, and a question that comes up from to time so it is good that it is being explored. pete Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted July 24, 2008 Report Share Posted July 24, 2008 Yeah, I hate when you have a nice, sane theory and reality just jump up and bite your behind… Off topic: The Fender “full Range Humbucker” is a very interesting pickup. It is not constructed very different from a Gibson HB. Remember that the Seth Lover that designed this pickup also invented the HB for Gibson. The bobbins are quite similar in size. They are also winded with 5000 turns each of AWG42. The resistance of both coils together is normally 10.6 Kohms. The pickup doesn’t have a bar magnet under/between the coils. The bobbins have six screws in each bobbin (no slugs like on a Gibson style HB). The screws themselves are made of the alloy CuNiFe (Copper Nickel Ferrite) that was chosen due to the fact that they could be machined to be screws. The setup more resembles two side by side single coils if the magnetic fields and flux are studied. The design also use less metal compared to a traditional HB, thus lowering the inductance and boosting treble. Unfortunately the Fender Blueprint that is shown as a facsimile in “THE FENDER TELECASTER” by Duchossoir doesn’t give away the dimensions of the bobbins and the pole pieces. Quote Link to comment Share on other sites More sharing options...
WezV Posted July 24, 2008 Report Share Posted July 24, 2008 Can’t really see how a pickup can be adjusted closer to the strings without a cover as the screws almost always protrude through the holes in the cover and thus are the thing limiting rising the pickups, not the cover. but I swear that I can get a tiny bit more height on my LP when I got the covers off, about the thickness of the air space and the cover on the slug pole...but again it is slight. if you remove the cover from a pickup then screw the adjustable poles back down into the coil you will have that little bit of extra height to play with i believe this makes a slight difference to the sound as well. with the covers off you can get the coils and magnets that little bit closer to the string and have the adjustable screws still well inside the pickup, this will create a differently shaped magnetic field to a pickup that has the adjustable screws protruding further from the coil. nothing worth worrying over though Quote Link to comment Share on other sites More sharing options...
psw Posted July 24, 2008 Report Share Posted July 24, 2008 Off topic: Yes...the fender full range is quite a bit bigger with wider, thinner, further apart bobbins and the internal magnetic poles are different to an HB. The whole pickup is quite a bit bigger and the staggered poles 3 out and 3 in on each coil make a bit of a difference too with a fair amount of magnet extending below the pickup in the covered part and adjustable from underneath giving a kind of pseudo slant. Lots more treble and bite but the distinctive sound has a distinctive "keraaaang" to it. And no noise! The new versions are in fact pretty standard humbuckers with offset screws but magnets below and the same size as a normal HB coils under fender style offset cover and so sound nothing like the original. All the same, there is a lot of mojo about them because of their rarity, commercially they were a bit of a flop. Compared to modern HB's they are underpowered, but then they are exactly as they were intended to sound, very "fender" yet like no other fender...if you get the idea. They don't sound anything like a gibson or other HB design. Yeah, I hate when you have a nice, sane theory and reality just jump up and bite your behind… Well I had some convinced...hehehehe Actually, you can say just about anything about pickups and someone will believe it. I bet someone could start a whole new trend with fancy covers claiming enhancing the sound in some way and make a mint on them as long as they look the business...maybe a little flywire mesh would do the trick! A good pickup maker should be able to get a pickup to sound as good with a cover as without but sonicly there isn't that much difference to my ear and the consumer goes a lot on looks. Fashion still dictates exposed coils. Now we see actual branding being of some importance these days too. Originally I came to PG with an aim to build pickups but got seriously distracted by the sustainer thing which I thought would come together fairly quickly. I was in fact prototyping aluminium constructed things with rare earth magnets powering 1/4" ball bearings as poles pieces. The top of the exposed bobbins were drilled out to expose the coils and the whole thing set in clear epoxy! The thing was quite an a work of art looking like something out of a machine or a surgical instrument from an alien spacecraft. A little tricky to make and I didn't get further than a single prototype. The whole concept was a work of art, really a lot of it was an aesthetic and trying to be different. As far as technically, the alloy bobbins are not the best idea (eddy currents) but the ball bearing things were pretty clever I thought. I never got as far as truly telling what they sounded like, but the design certainly looked cool. I bet I could have convinced a lot of people that they were the best thing out there even though (or maybe because) they disobeyed all the design rules. Anything with rare earth magnets in them has got to be "special" cause...well they're "rare" and the partially exposed coils mean you can see the workings and my haphazard scatter winding, so you know they are going to be good. ball bearings...errrr...special spherical magnetic field...ohhh I think I want one! Definitely a case of form over function! I am a little surprised that custom makers don't attempt more radical designs outside of the standard single and HB sized packages. There is a lot to be said for quite different pickups on a single guitar as well to get more range of sounds from an instrument. I am also a little surprised that not more is done with active electronics such as is common with bass instruments. In truth, just about any coil and magnet will make a sound and it is a matter for the player to make best use of the things...IMHO If anyone is into patents (I seem to be cured) Lace have any number of them with a huge variety of construction techniques many that never see the light of day. I know one used special rubberized flexible fridge magnet materials in them for instance. As always...all theories are my own or based on hearsay and so are open to discussion, criticism or contention... pete Quote Link to comment Share on other sites More sharing options...
dpm99 Posted July 24, 2008 Report Share Posted July 24, 2008 Actually, you can say just about anything about pickups and someone will believe it. I bet someone could start a whole new trend with fancy covers claiming enhancing the sound in some way and make a mint on them as long as they look the business...maybe a little flywire mesh would do the trick! pete You could definitely make some big money on that. Just make sure you have some very scientific pictures of sound waves between the pickup and the strings. I think that's the secret. Quote Link to comment Share on other sites More sharing options...
kpcrash Posted July 24, 2008 Report Share Posted July 24, 2008 Instead of flywire mesh - what about edible pickup covers? that way, you would have recurring income when refills were needed. Quote Link to comment Share on other sites More sharing options...
DGW Posted July 28, 2008 Report Share Posted July 28, 2008 I'd like to add covers ... Can someone tell me where to get the wax and how to do it? Do I need a melting pot or is there another way? Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted July 28, 2008 Report Share Posted July 28, 2008 I had the opportunity to talk this over with some other guys and one of the most interesting information I got was this: The cover acts as a shorted turn, so it lowers the inductance and lowers the Q of the resonant peak somewhat. Because it's non-magnetic metal, it doesn't have any effect on the magnetic circuit that would increase the inductance. The rule is that non-ferrous metals lower the inductance and ferrous ones increase it. DGW: http://www.stewmac.com/freeinfo/Electronic...indyfralin.html Quote Link to comment Share on other sites More sharing options...
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