A really really thin mag pickup

[salvarsan]

In my estimation...

Yo, Mark.

I just did some estimations with my spastic coil winder application
with Strat bobbin pole spacing but core height compressed to 1/16".

The core L,W,H and flange dimensions become 2.25",0.188", 0.062", 0.625".

Compensating for different coil space fill factors of scatter wind
vs. hexagonal "perfect lay" (62% vs. 90%), here are some numbers
for a full bobbin:

handscatter: #38 423 winds, 122 ohms, 39 layers, 10.8 turns per layer
hexagonal : #38 615 winds, 175 ohms, 47 layers, 13.1 turns per layer

Since neodymium magnets have a permeability close to 1.0, you could
probably figure the inductance and 1000Hz impedance of an equivalent
air core inductor (are either one of you Joe's watching?).

-drh

[bbsailor]

Yes,

Reporting for duty!

Joseph Rogowski

Maybe using a current sensing transformer attached to one loop of AWG 12 wire wraped around a neo magnet .25" wide x 1/16" thick and 2" long will work as long as Mark can fit the matching transformer close to the pickup, under the pickguard.

Mark, does the top of the guitar arch so that the outer edge of the pickguard has some space under it?

JR

[Mark Hammer]

Here's a cropped and rotated picture of the critical area. You can see (maybe) it is essentially the height of the fingerboard plus whatever clearance is provided by the frets.
And yes, Joe, there is a most delightful arch to the top. I have some 100k thumbwheel pots cannibalized from my first electric (a delicious, but long gone, 4-pickup Kent). perhaps they can be used.

[bbsailor]

Here's a cropped and rotated picture of the critical area. You can see (maybe) it is essentially the height of the fingerboard plus whatever clearance is provided by the frets.
And yes, Joe, there is a most delightful arch to the top. I have some 100k thumbwheel pots cannibalized from my first electric (a delicious, but long gone, 4-pickup Kent). perhaps they can be used.

Mark,

You are right. This is a challenge!!!

If you make a pickguard out of 3/32" thick plastic with an extension the size of a Humbucking pickup mounting ring, would it fit under the strings? Mounting a thin pickup depends on the pickguard as described above fitting the available space.

How much space would be under the lower part of a pickguard near the side of the body where it could have the largest space?

What is the height of each string above the body when the string is pressed at the last fret?

What is the height of each string pressed at the last fret over a flat piece of plastic 3/32" thick laying flat under the strings .25" from the fingerboard end?

Joseph Rogowski

[Mark Hammer]

You ask a lot of good questions I have none of the answers to yet. I'll try and get some answers later this week.

[Alabam]

Here is a pic of a thin pickup i wound some time ago, the dimensions were,
core width 3/16", bobbin covers 1/32" thick, so it can be done.
An earlier one i wound using the same 44AWG wire gave me 5.10 K ohms, its core was 1/4".
Good luck with your effort.

[Instigator]

A thin pickup? The early '70s Rick 4001 copies made by Kay had great-sounding pickups in oversize, ugly-looking covers which had short - roughly 5/32" tall - bobbins wound to 4.0 K and gaussed by equally thin but strong bar magnets fitted inside the bobbins.

[Alabam]

A thin pickup?

Is this the Rick 4001 guitar you mean?,
Its a copy, going for $495 at http://www.retroguitar.com/inventory.htm

[Instigator]

Not at all. That's probably an Ibañez or the like. No, the Kay copies were short-scale, crude-looking, and crudely made. And they certainly aren't worth 400 bucks - 100 is more like it. I wish I had a couple pictures of one to post, but I don't.

[Martin Beer]

Sorry if it's bad manners to bump a year-old thread, but I've been messing around with winding a pickup for a Kalamazoo archtop very similar to Mark Hammer's, and I tried some of the ideas from this thread. I'm using six 5mm diameter x 3mm high neodymium button magnets, glued between pieces of 0.8mm vulcanised fibre to form the bobbin, so the whole thing is just under 5mm high. This sits at the end of the fingerboard nicely, just using a small piece of double sided tape.
I first tried winding with 44 AWG wire, and found I could only get up to about 3.5k ohms without the coil being ridiculously wide. Unsurprisingly, it was pretty weak sounding and low output.
I then tried the low impedance approach with 40SWG (about 36 AWG?) wire wound to around 80 ohms, then used a cheapy mic matching transformer before my amp. This approach is the winner, in my opinion. The output is a little less than my other guitar (with SD jazz humbucker), and the sound is totally usable. It's less midrangey then the Duncan, with a clear, pleasant open sound which keeps a lot of the character that the guitar has acoustically.
This is my first attempt at winding any pickups, using a very crude setup consisting of a cordless drill with the pickup attached to a small disk intended for sanding disks, and the wire spool sat on the floor by my feet. Not ideal, but it seems to be working for me!
One problem though, the CA glue I used doesn't bond very firmly to the magnets. Has anyone found an adhesive that works well for plated magnets - maybe a 2 part epoxy?
I'll try to post some pictures of the final pickup that I install on the guitar. Thanks to everyone whose posts gave me ideas!