Magnets & Copper Wire: A Pickup Building Thread

#1,821
Alright, I’ve made the working prototype, and possible working model, for the mid position pickup for my oddball bass build. It isn’t groundbreaking in any sense, and incorporates a lot of the elements I learned from everyone in the previous discussions. Thank you for all your insight and willingness to share!

it is a split coil hum-cancelling unit. I was going for a hot jazz bass winding between both coils, and I think I achieved that at 8.38k. I did order some thinner gauge wire, but since these are going to be completely concealed, I used the full height of the 1/4”x1” magnets. The coils are very tall, but I was able to use 42 gauge wire to get 9,000 winds on each coil.

I have done a lot of research since the last conversation, and from what I gather:

-Smaller wire means more winds in the same area, but higher resistance.
-Higher resistance leads to decreased highs and increased lows in general.
-Stronger magnets can accentuate brightness.

So I’m going for a higher resistance, using the magnets to hopefully reclaim some brightness while reaching up through the body and giving a similar output to a standard bass pickup.
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I went with the 1/4” magnets for two reasons. I used them for the monster single and they worked on my test rig, and I need a way to balance the bridge pickup with the mid pickup, since I won’t really be able to adjust them much (if at all). I’ll need to make the bridge pickup more powerful.

For the bridge, I’ll be going for a slightly higher wind count, and I am using 3/8” magnets in a similar form factor.
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These are really strong magnets. They are all a pain to work with!
 
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#1,822
I squeezed 11k windings on this, reads 5.1k. That lines up with the other ones I just put together, which were both about 4.2k, and doubled when wired in series.
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Does length of coil have anything to do with resistance? The single coil I made measured over 9k, but I don’t know how many winds it had. It doesn’t seem like it could have been that much more than 9-11k, but that’s just a gut feeling. I am trying to wrap my head around the big difference in resistance between the big single coil and this last one.

Also, I don’t think I will ground the pole pieces, all the research I see says in general it is to avoid noise when they are touched. Since mine cannot be touched, I figure it is unnecessary. However, if someone had other info I would love to hear it!

Edit: I just realized I asked a question that should have been obvious. Number of winds vs area. 10,000 winds on a bigger area is more wire. I’ll leave the question up for others to stumble on in case they were thinking the same thing.
 
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#1,823
Verner said:
I squeezed 11k windings on this, reads 5.1k. That lines up with the other ones I just put together, which were both about 4.2k, and doubled when wired in series.
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Does length of coil have anything to do with resistance? The single coil I made measured over 9k, but I don’t know how many winds it had. It doesn’t seem like it could have been that much more than 9-11k, but that’s just a gut feeling. I am trying to wrap my head around the big difference in resistance between the big single coil and this last one.

Also, I don’t think I will ground the pole pieces, all the research I see says in general it is to avoid noise when they are touched. Since mine cannot be touched, I figure it is unnecessary. However, if someone had other info I would love to hear it!

Edit: I just realized I asked a question that should have been obvious. Number of winds vs area. 10,000 winds on a bigger area is more wire. I’ll leave the question up for others to stumble on in case they were thinking the same thing.
Click to expand...

In my experience & knowledge, increasing the resistance through the coil, while keeping everything else the same, mainly changes the shape of the EQ curve. Almost all pickups have a big lump in the curve, usually centered in the mid-high range. Changing the resistance, alone, raises or lowers the height of that lump, and may shift the center of the lump.

For example: Same bobbin, same magnets, same number of turns, but trying different wire gauges. The output level will be about the same. The #43 wire will have the highest resistance, and it will have the highest lump in the EQ curve. The high-mids will be louder than the rest. Using #40 wire will reduce the resistance, which will flatten the curve out. Not to completely flat, but a much lower lump. The overall output level will be about the same, but you'll hear more lows and highs.

This can get confusing because when most people are comparing pickups based on resistance, the pickups have different turn counts, in addition to different resistance. That is, a pickup has been made "hotter" by adding 2000 more turns of the same gauge wire. So that increases the overall level and increases the lump. Everything is louder, but the lump is more louder.

If you go with more turns using larger wire, you will increase the overall output level at the same or lower resistance. Louder and a flatter curve.

This is how you adjust the sound of a pickup design, using combinations of wire gauge and number of turns. The number of turns sets the level, and the wire gauge adjusts the overall shape of the EQ curve.
 
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#1,824
Bruce Johnson said:
In my experience & knowledge, increasing the resistance through the coil, while keeping everything else the same, mainly changes the shape of the EQ curve. Almost all pickups have a big lump in the curve, usually centered in the mid-high range. Changing the resistance, alone, raises or lowers the height of that lump, and may shift the center of the lump.

For example: Same bobbin, same magnets, same number of turns, but trying different wire gauges. The output level will be about the same. The #43 wire will have the highest resistance, and it will have the highest lump in the EQ curve. The high-mids will be louder than the rest. Using #40 wire will reduce the resistance, which will flatten the curve out. Not to completely flat, but a much lower lump. The overall output level will be about the same, but you'll hear more lows and highs.

This can get confusing because when most people are comparing pickups based on resistance, the pickups have different turn counts, in addition to different resistance. That is, a pickup has been made "hotter" by adding 2000 more turns of the same gauge wire. So that increases the overall level and increases the lump. Everything is louder, but the lump is more louder.

If you go with more turns using larger wire, you will increase the overall output level at the same or lower resistance. Louder and a flatter curve.

This is how you adjust the sound of a pickup design, using combinations of wire gauge and number of turns. The number of turns sets the level, and the wire gauge adjusts the overall shape of the EQ curve.
Click to expand...
EXTREMELY helpful and equally interesting. I am excited to test this out!


Speaking of which, I finished the second bridge set with the big magnets, measures 10.2k in series. I took them out to my super-scientific high-tech testing platform and I am happy to say that the overall output is comparable to my jazz bass 1/2” away from the strings with 1/4” of wood between. If I rout down a bit more the output increases exponentially, although given the strength of the magnets that may increase the pull on the strings to an undesired level.
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So I think I have a basic form, now I need to create a baseplate, templates, etc. one problem here, and a reason I probably can’t use these as a final version, are the weaknesses inherent in the PLA 3D printed plastic. It is made to be easy to melt, which makes wax potting questionable. It probably wouldn’t melt the flatwork, but there is a very good chance it would warp and distort it. I’ll test it out on a dummy piece, but I imagine I’ll need to make final pickups out of vulcanized fibre. At least I have templates to work from.
 
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#1,825
One other way to increase the magnetic field strength to a degree, other than using bigger magnets, is to fix the magnets to mild steel.

Im doing that in most of my designs, and figured this would also be an opportunity to show my Darkstar/Bisonic/Ric-inspired design:
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It’s a big ol’ single coil, with ceramic magnets butted up against a laminated steel core. Like the Bisonic design, using laminations helps reduce eddy currents which can sap some of the highs.

But even using a small piece of steel, say, on the bottom of your magnets can help increase the strength a bit if needed. And it’s also just another variable to play with in shaping the tone.
 
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#1,826
slowburnaz said:
One other way to increase the magnetic field strength to a degree, other than using bigger magnets, is to fix the magnets to mild steel.

Im doing that in most of my designs, and figured this would also be an opportunity to show my Darkstar/Bisonic/Ric-inspired design:
View attachment 5488040 View attachment 5488041 View attachment 5488042

It’s a big ol’ single coil, with ceramic magnets butted up against a laminated steel core. Like the Bisonic design, using laminations helps reduce eddy currents which can sap some of the highs.

But even using a small piece of steel, say, on the bottom of your magnets can help increase the strength a bit if needed. And it’s also just another variable to play with in shaping the tone.
Click to expand...
That is so cool, and really interesting, I’m going to have to look into this more as it could be directly applicable to my situation, thank you!
 
#1,829
ardgedee said:
A very long very skinny length of wire will show high resistance regardless of where it's sitting.*

*(unless it's sitting in a bath of liquid nitrogen.)
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:laugh:

It's all relative I guess. Copper never becomes superconductive so I would only go so far as to say that a very long very skinny copper wire will show a less high resistance when sitting in liquid nitrogen!
 
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