A deeper look
On the face of it, extremely simple bits of kit – stick some magnets in the holes, boards on the top and bottom… wazz some wire on there, and you’ve made a pickup! Lovely!
But like most things with guitars, whilst on the whole its pretty straight forward, there are always a few things that make them a bit weird.
1.Pole spacing
Fibre boards “officially” come in one pole spacing, 52mm, measured centre to centre, E to e pole. It's what was used on the first Stratocaster®, and it’s lasted the test of time.
Weirdly – it’s not actually “correct”. Pole spacing with pickups is pretty academic, the poles don’t have to line up with the strings, simply because it doesn’t change how they sound, and most guitars are slightly out either way. However, on the original Stratocaster®, they were VERY “out” – string spacing at the saddles was 56.4mm, and by the point of the strings hitting the neck, they’re around 50mm. Usually, only the middle pickup aligns perfectly with the string spacing.
Now, that’s only on older guitars (and their subsequent re-issues!) because they were fitted with “wide” bridges! When we get into the late 80s, we see the “modern” Stratocaster® turning up with narrower string spacing at 52.38mm at the saddles - and again, the poles don’t line up!
But, obviously, that doesn’t matter one lick. Fender® didn’t bother changing the pole spacing because they’ve never lined up. Any change they made would have been purely cosmetic.
HOWEVER – when Squier® finally joined the party (and they stopped making very good historical reproductions!) around the mid 90s, they were using 52.38mm spaced bridges. Seemingly, the pole spacing vs. string spacing bothered them… and they reinvented the wheel, releasing neck and middle pickups with 50mm and in some cases, 48mm pole spacing. The poles now lined up with the strings!
Looks lovely, but it changes the way the pickups sound!
A 50mm spaced pickup has a different internal length to a pickup with 52mm spacing – its shorter, so every “wrap” of wire is shorter too, and as such, has a lower resistance.
Assuming both pickups are wound with the same number of turns (which they are!) A 50mm single coil is now weaker, with a higher resonant peak, and a lower inductance compared to the 52mm version.
Whilst we're on the subject of single coils spacing , bear in mind that when we speak about pickups being 52mm, 50mm and 48mm spaced… this isn’t quite accurate. Officially, they’re 52.2mm, 50.2mm, and 48.2mm!
Its actually not uncommon to build up a single coil frame, test fit it in a cover, and have it not fit! What actually happens is this – when the copper goes on there (about 8000 - 9000 turns usually) it compresses the poles and causes the boards to deform – closing them up by a fraction of a mm, and turning them into the “correct” spacing’s.
2.Pole Diameter
This one catches everyone out at some point or another. Single coil poles come in potentially three different widths – 3/16” (4.75mm), 5mm and ¼” (6.35mm).
Originally, when single coils were made in the USA, imperial dimensions were used, and 3/16” was correct.
When production moved out into Japan/Korea/China, as often happens, there was a rounding error, and fibre boards/poles changed from 3/16” to 5mm.
It didn’t seem to catch on with USA produced guitars, but it did everywhere else and 5mm poles are VERY common nowadays.
It usually doesn’t cause any problems, as the covers are interchangeable between 5mm and 3/16” pickups, possibly the covers were always intended for 5mm poles.
However, it does make a difference to the sound of the things!
A pickup made with 3/16” poles has a smaller internal length and width compared with one made with 5mm poles, in the same way a 50mm spaced pickup does compared with a 52mm. You’re saving 0.25mm, which sounds tiny, but that’s enough room to fit approximately another 1000 winds on there, and tonally, that’s huge!
Also, because the poles are smaller, they contain less Iron, and as such that reduces the pickup's inductance too.
Essentially, a pickup with 3/16” poles is a completely different beast to the same coil on a 5mm pole pickup! It's normally a little brighter, a little more biting, with a higher resonant peak and a higher Q factor.
However, a 3/16” poled pickup could potentially be wound with 10% more turns. It’s a small variable, but could result in big changes!
A further variation on this to be aware of is the ¼” pole. When constructed, the internal measurement will be 1.35mm wider AND longer, compared to the 5mm poled version. Essentially, you’ve lost the space for approximately 4000 winds, and these are huge poles, containing more iron, meaning higher inductance!
3. Colour
Traditionally, Fender wound all single coils using Black fibre boards until 1964. When they switched over to Plain enamel coated wire, it was harder to see the wire against the boards, so they switched over to grey boards on the bottom.
Nothing overly sinister about it, just something to make the winder's life easier!
From 1982, we occasionally see Red boards too – I can’t say I know much about them to be honest, but I imagine it was a similar reasoning. They’re pretty rare either way, and it would be nice to carry them, but I’m a little more interested in different sizes and shapes than I am in board colour at this point.
4. Shape
So, we’ve got three pole sizes, three pole spacings, potentially three colours… lets make it really fun! Lets have different shapes too!!
Traditionally, single coils are that shape we all know; a soft, triangular “thing”, with two holes for the eyelets at the bottom/front, and two screw holes either side for the height adjustment bolts. However, there are “side loader” single coils too! Boards where the base is a long “stick”, with the eyelets built into the ends near the mounting bolts.
Honestly, the reason why side loading boards were invented is unclear. Whilst they offer a smaller footprint without reducing the coil space, the fact is that most of these pickups are going in guitars that are near perfect copies of the original Fender® Stratocaster®, which should take the normal boards.
That being said, you do get single coils in guitars that aren’t based on the Fender® designs – pickups mounted in very tight, small routes – so I suppose that’s where the side loading boards come into their own!
5.Covers
This is a question I feel like I answer every couple of days, so lets break it down a little bit;
A.Compatibility
It’s as you imagine really; a 52mm cover is going to fit a 52mm fibre board, a 50mm fits a 50mm, a 52.5mm will fit a 52.5mm. Covers are designed to fit over 5mm poles, so they’ll accept 3/16” poles, but ¼” poles require specialist covers.
B. Colour
52mm spaced covers come in the widest range of colours – reds, blues, greens, pinks, parchments, ivory, black, white, silver, gold, beige with black spots… you name it, it’s available in 52mm!
All those lovely “Fender®” colours? They’re 52mm! Maddeningly, these colours aren’t available in 50mm, 48mm or 52.5mm spacing. The factory that makes all those nice Fendery colours doesn’t have the moulds for the other sizes; the factory that make the 50s/52.5s doesn’t have access to the specialist colours. So, if you're insisting on having a 52/50/50 set? Get your heart set on Black or white covers too!
C. Mounting
This isn’t really covers or fibre boards “thing”, but it’s slightly interesting either way. The mounting holes on single coil boards DO NOT line up with the holes in the pickguards. – The holes in the guard for the height adjustment bolts are spaced at 78mm (and the holes in your pickguard should be 4mm diameter) but, the spacing on the pickups themselves is 76.5mm!
This is actually, entirely intentional, and has been that way since day one. I can't say I know for certain why, but I’d imagine it’s to drive the screw in at a slight angle to give a better “grip” in the threaded holes. The 6/32 UNC bolts used for mounting single coils are just over 3mm wide, so they sit slightly “in” on the 4mm holes in the pickguard, but you do get a slight angle on there. Most people never actually spot it, but if you look back at an old Stratocaster®, you can see that the counter sunk bolts used up until 1988 sat a little “wrong” in their recess, and was probably why Fender moved away from them towards dome head bolts.
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