magnetic pickup for gypsy jazz guitar

[StarryNight]

I'm thinking of making a pickup for my manouche guitar somewhat similar to a floating Benedetto pickup made out of wood. It would attach to the end of the neck and sit on the soundboard between the sound hole and the neck. I'm thinking of using 6 1/8" x 1/8" neo magnet rods and probably some 42 HF. I've never worked with neodymium before so i don't know if that size of rod will be strong enough or too strong. Can anyone forsee problems with this design idea? I'm not even sure how many winds it would take and if I should use a thinner guage to beef up the signal. Any ideas welcome!
thanks...

btw, there is about 7/16" of distance from the guitar top to the bottom of the strings

[David King]

It should work but you may need to adjust magnet heights to get a balance across the strings. If you used alnico you could adjust amplitude by demagnetizing rather than having to move the magnets up and down. No way to demagnetize neodymium.

I've heard that taller magnets have proportionally taller fields, something to consider. Also limiting your coil height to 1/8" will severely limit the number of turns of 42 or will cause the turns to be so far away from the magnets as to quickly lose some umph. I'd wind the coil on a rigid bobbin and then pop the flat work off after you've potted the coil so that it will remain as thin as possible with the greatest number of turns.

[StarryNight]

It should work but you may need to adjust magnet heights to get a balance across the strings. If you used alnico you could adjust amplitude by demagnetizing rather than having to move the magnets up and down. No way to demagnetize neodymium.

I've heard that taller magnets have proportionally taller fields, something to consider. Also limiting your coil height to 1/8" will severely limit the number of turns of 42 or will cause the turns to be so far away from the magnets as to quickly lose some umph. I'd wind the coil on a rigid bobbin and then pop the flat work off after you've potted the coil so that it will remain as thin as possible with the greatest number of turns.

Good points! I assumed the neos would be so strong they wouldn't need much wire. I've got some 43 guage which might work better. These guitars are supposed to be bright sounding so it might work out having less wire than more. I'll post some updates once i start building. Thanks for the advice...

[David Schwab]

You can stick those short magnets to some steel rods to make them taller. They will be more efficient that way as well.

[David King]

Those guitars are bright sounding, there isn't any doubt about it but you might not want a bright sounding pickup to go with it. You might find that a darker pickup is just right. You won't know until you start winding and trying. I would shoot for 5000 turns for starters.

[David Schwab]

I agree with David. The neo magnets will allow you to wind it hotter for more low end, while still having a nice top end. Neos sound more like alnicos than ceramics, as far as the warmth factor, while having crisp highs.

[StarryNight]

great ideas. thanks guys. I never considered placing a bar under the magnets to raise the height to get more winds around the magnets and increasing the magnetic field . 5000 winds will be challenging I think. I guess the two options for the bobbin are using fiberboard or try to mill one out of wood. I'll do some experimenting this weekend and post some pics.

thought: I wonder if i could epoxy fiberboard right on top of the mags and get more space for wire?

[David King]

Starrynight,
you can use anything you want for the top and bottom plates of your bobbins. I like the very thin formica that I laminate back to back for a stiff flatwork that won't warp.
You can also wind between two spinning disks and then carefully pot the wire coil in CA glue to have a bobbin-less coil that you slip into a cover. This is the way lipstick pickups are made and will save considerable vertical space.

[David Schwab]

great ideas. thanks guys. I never considered placing a bar under the magnets to raise the height to get more winds around the magnets and increasing the magnetic field .

You can also try the magnet under the pole.

5000 winds will be challenging I think.

What gauge wire are you using?

[StarryNight]

DK - Formica! that would be even thinner than fiberboard - great idea. Winding without a bobbin would be a challenge. I'm not set up with plates on either side of the magnets as I wind, but with a little rigging it might be worth a try to reduce height. talk about delicate though! I guess wax paper would keep the wire from sticking to the plates when applying the CA?

DS - the smallest guage I have is 43 HF. The string spacing on the guitar is fairly wide so I'll have the advantage of length to increase the amount of wire somewhat. It just occurred to me that I need to make this pickup even more shallow than originally thought as the playing style used for these guitars is fairly hard with aggressive picking technique. I've got lots of room width wise, but as mentioned earlier the further out from the magnets the less effect on the gauss strength - something else I neglected to consider! geez... it's so easy when you just order the parts!

I'm going to try and keep the whole thing no more than 1/4" high if I can. More to come...
thanks again,
Tony

[David King]

Tony,
One way that might improve the field strength of the magnets towards the outside of a wide, flat coil is to put extra magnets and/or iron along the outside edges of the coil. This is the way a Lace sensor pickup works, the coil is on the inside, wrapped around a steel "comb", the comb is essentially a horseshoe circuit for the flexible magnets that are stuck on around the outside of the coil.
Lace uses very fine wire for a very small, low profile coil.

Any type of mold release on your winder plate should allow CA to pop right off.
I have used wax paper for this and it's pretty reliable until it gets totally saturated. It will stick eventually if you aren't careful. A wipe of car wax under the paper will guarantee success.

[StarryNight]

update

hey guys,
I started the process and so far have succesfully wound a bobbin-less pickup with the advice of everyone here (couldn't have done it with out you)! After getting the 1/8 x 1/8" neos I discovered that they fit perfectly in a humbucker spacer bar. I had 10 magnets but only 8 holes in the bar so I drilled 2 more holes and rounded the ends of the bar. I then added to the height by gluing a thin piece of galvanized steel to the bottom (an electrical box cover plate) and sandwiched the whole thing in between two plates of aluminum (an old ruler). I covered the aluminum in paper and used a little walnut oil so they would detach when the time came. after spinning the wire over the magnets I used CA glue to stiffen the winding, removed it from the winder and used a hot iron on the aluminum plates to release them from the winding. I screwed up the first attempt and the wire broke on me. The second time 'round worked and the whole thing actually fits inside the pickup cover! Pictures can be seen here: http://photoshare.shaw.ca/messages/v...gallery/page/1 (there's a few pics of a new bridge I made - just ignore those...)

I managed to get 6000 winds of 43 HF which came to 5.8k. I haven't actually heard the pickup yet - It might sound like crap, who knows. In hindsight I thought I should have made a split-humbucker but I don't know if I would have had enough room. I'll post some audio clips if it actually sounds decent...

[David King]

That looks pretty cool. I love it when we suggest a totally wacky and untested idea to someone and it actually works out for them.

Something to know about CA glue, it was designed originally for bonding skin as a way of quickly dealing with battlefield injuries during the Korean war. CA actually bonds quite nicely in the presents of oil. You might try some form of silicone as a mold release if the need arises again.

[David Schwab]

That looks really good. That's a sweet guitar! Make me wince when you were cutting the end of the fingerboard off!

[StarryNight]

That looks really good. That's a sweet guitar! Make me wince when you were cutting the end of the fingerboard off!

Tell me about it. I don't think I've ever cut something so carefully. The curved veneer knife helped.