7 String Pickup winding

[Newbie]

Hello pickup makers,

I'm new here, sort of. I actually posted on the old 'ask the pickup makers forum' some 20 years back when I first started this project before life happened and the project got shelved.

Apologies ìf this has already been asked, I did search, but didn't find any similar topics.

I'm planning to wind some 7 string single coil pickups, with vintage 1950s/early 1960s tone (for 1970s classic rock and 1990s alternative rock).

What I want to ask is about the extra length of the bobbin and how that effects the number of winds. On the one hand if I wind to the traditional number of winds, it would make the overall wire length longer due to the longer bobbin. On the other hand if I compensate with fewer winds it would result in a thinner coil width, and less wire passing through the area of magnetic disturbance. I'm guessing it's one of those things where compromise is necessary, but I am wondering which approach will get me closer to vintage tone?

Thanks for any guidance.
Matt

[big_teee]

Welcome to the forum.
After reading your post, I did some calculating.
I had the data for a 1955 strat pickup wound with 42HV.
So I duplicated that data for a 7 string.
I based the bobbin length on .402 between strings, and .187 diameter magnets.
I would try the same amount of turns for a 7 string as for the 6 string.
Here's what I came up with.
You could also come up with something else, using 42 Single wire.
BTW what pickup position are you winding for?
Neck, middle, bridge or all?
Here's the attachments I made, and data I came up with!

[Newbie]

Thanks Terry,

It looks like something may be missing from your post under 'here's what I came up with' (?).

I'm winding for all three positions.

The magnets I have are about 0.2" diameter x 0.71" deep (I ordered 5mm x 18mm) Alnico V. I got them at a time when there was less data online, and had no clue about staggering etc, although I think I could stagger to the shorter lengths just by pushing the magnets further into the bobbin past the base of the lower flatwork. The magnets are a lot weaker now than when I bought them, though that may be desirable anyway.

The wire I have is 0.063 (which is 42 AWG) Enamel. Not sure why I didn't get Formvar.

Matt

[big_teee]

I was referring to the attachments I made, listed at the bottom of the post.
Here's another estimate attachment design, for .2" mags, and 42PE, or 42SP wire.
The .435" is the height of the magnets, between the fiber flats.
The listing would be good for a bridge pickup, I would reduce the middle to 8000 turns, and reduce the neck to 7850, or so turns.
GL,
T

[Newbie]

Thanks Terry, I'm not sure why, but all I get is a small image of a paper clip and the words "Attached Images", there's no hyperlink. Tried on my phone and PC, but no luck.

[Newbie]

Yes that worked thanks Terry. Just curious, what is the spreadsheet you're using there?

[big_teee]

It's a modified estimator program built by another moderator. DrStrangelove.
I use and converted my version, into a pickup bobbin library.
Glad I could help.
GL,
T

[zparts]

Hello pickup makers,

I'm new here, sort of. I actually posted on the old 'ask the pickup makers forum' some 20 years back when I first started this project before life happened and the project got shelved.

Apologies ìf this has already been asked, I did search, but didn't find any similar topics.

I'm planning to wind some 7 string single coil pickups, with vintage 1950s/early 1960s tone (for 1970s classic rock and 1990s alternative rock).

What I want to ask is about the extra length of the bobbin and how that effects the number of winds. On the one hand if I wind to the traditional number of winds, it would make the overall wire length longer due to the longer bobbin. On the other hand if I compensate with fewer winds it would result in a thinner coil width, and less wire passing through the area of magnetic disturbance. I'm guessing it's one of those things where compromise is necessary, but I am wondering which approach will get me closer to vintage tone?

Thanks for any guidance.
Matt

From my experience it's best to wind the same number of turns as you would the 6 string bobbin onto a 7 string bobbin. Yes the resistance is higher because of the longer bobbin, but the tone remains the same. Trying to reduce the turns to match the DCR of a 6 string affects the tone more than if you keep it the same.

[Newbie]

Thanks zparts, that's very reassuring for me.

[big_teee]

Thanks zparts, that's very reassuring for me.

I also said that in post two, to go by turns not DCR.
It's unanimous!
Could you list your exact bobbin core dimensions in inches decimal, for my records?
T

[Newbie]

Yes you did, thanks very much for all the time you've taken on this Terry. I don't have a bobbin yet, still trying to find a source of forbon in Australia. When I do I'll cut the flatwork from scratch. It's part of a guitar I'm building, so even the string spacing isn't set in stone yet. I'm likely to build according to 6 string stratocaster pole piece spacing, just extending the length of the flatwork to accommodate a seventh pole piece at the same spacing. I'm also deviating from standard design to add a coil tap or two to each coil.

[big_teee]

What about the string spacing at the nut, and the bridge, is that determined yet?
T

[Newbie]

Not exactly (I'm making an acoustic style bridge with a piezo under the saddle), but it'll be strat dimensions + an extra string wide. I don't mind if it results in a wide neck, I've been playing Spanish guitar and banjo mostly for the last decade, so I'm used to both wider and thinner necks.