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Winding your own jm pickups?

Posted: Mon Jan 04, 2021 11:27 am
by hartwekk
Hi folks,

Just wondering about anyone's experience winding their own JM pickups. I picked up a JM kit from a manufacturer where I was able to choose the magnets (A2, A3, A5), pole orientation, bobbin color etc. I opted for A3 in both neck and bridge, North in one, South in the other so I could RWRP, wound 8500 wraps with plain enamel wire - no wax. They came out sounding much more JM than the stock pickups (MIJ Paisley 2017) but lack some girth. So, I would like to roll up another set but am curious what others have done or would recommend? Mix the Alnico magnets between pickups e.g A2 on neck A5 on bridge? Mix them on the pickup itself? Wire changes? Wraps? I think the 8500 was too low, myself, but wasn't sure how much wire I had left on the spool! The resistance on both was around 7.5K, and should be higher I think.

Comments?

Re: Winding your own jm pickups?

Posted: Mon Jan 04, 2021 2:02 pm
by Veitchy
Mixing magnets between the two pickups is relatively common, even 'back in the day'. I think the first LP customs with the staple P90s were A2/A5 neck/bridge from memory. It can be an effective way of getting subtly different voicings in the two positions.

Re: Winding your own jm pickups?

Posted: Wed Jan 06, 2021 11:03 pm
by epizootics
That 'lack of girth' you describe probably has to do with the magnets. Alnico 3 is fairly weak gauss-wise, it's one of those that I always find to sound sweet on its own but lacks body when compared to other similar pickups using other grades of Alnico.

Going with A5 in the bridge and A2 in the neck is a good option indeed. You can also underwind the neck pickup by 500-700 turns to keep the output balanced between the two pickups. Remember that a lot of the early pickups were wound until the bobbin was full, which accounts for a pretty wide variation in turn count, inductance and DCR. The trick with JM pickup is to find the right tension when winding. Too little and the coil will be full too soon. Too much and it'll flare like an overfilled sandwich. 8500 turns / 7.5Kohms is pretty standard. An extra 500 turns will lower the resonant peak by a bit and your pickup will sound a bit 'beefier'.

There is less room for that on JM pickups than other designs, but here's a trick of the trade: the closer to the core of the bobbin, the more your winding pattern will have an effect on the sound (that's where the magnetic field is the strongest). If you want to go 'full-tilt scatterwind', you only need to do so with the first 2000 turns or so. After that, you can go back to a more civilized, ordinate winding pattern, which will allow you to fit more wire on the bobbin. You may or may not want to do that depending on what you're after - crazy scatter will reduce the inductance some, thus raising the resonant peak.

If you don't do that already, make sure you tape off the magnets before you start winding. This is an extra insurance down the line - the hard surface of the magnets can wear through the insulation over time and cause shorts. So is a bit of potting, to prevent the vulcanized fiber from absorbing ambiant moisture and deforming through time, as well as keeping the wire from moving too much, at least in the outer layers. If you don't want to wax pot or don't have the equipment (which is quite minimal - a tin can and a pan of boiling water!), you can give your pickup a quick dip in shellac. Put it in, take it out, let it dry for a bit, and repeat a couple of times. It won't do much for microphonics but will at least seal the flatworks.

One thing I'd suggest is that you buy a big spool of Polysol wire. It's a lot cheaper than PE, as well as being sturdier. As long as the insulation thickness is the same, the material makes no difference. With a 4lb spool, you won't have to worry about how much you have felt on it for a while :) Once you start winding your own, it is usually really hard to stop and go back to buying pickups.

There are many factors you can play with: bobbin thickness, magnet type and size (I like the extra bite provided by 0.63" in a JM pickup - you just need the extra bit length to stick out at the bottom of the pickup), wire diameter and insulation thickness, winding patterns, etc. Welcome to the world of tiny wires & diminishing eyesight ;)

Re: Winding your own jm pickups?

Posted: Wed Jan 13, 2021 11:42 am
by hartwekk
Hey Epizootics,

Thanks very much for all of this info - I wish I had thanked you sooner but I've been a bit tied up with work.

I think I will wind another bridge pickup with a few hundred more winds. I still had room on the bobbin (probably enough for 500 - 700 winds) so my tensioning seems okay. The A3 in the neck is actually quite good.h my I had initially tested the pickups on my Pignose and they sounded good but when I played through my 70's ultra linear Twin Reverb I was in shock how good the pickups sounded. But because they were wound to the same amount of turns, the bridge has a lot less volume - and still lacks girth. I think A5 would be best for the bridge.

I don't have a tensioning system apart from my hands and some felt so its a bit of a challenge to keep it uniform. I have a bit of arthritis in my hands so I tend to adjust wind speed up and down depending on my grip and I hate breaking wire. On that, the polysol is a better option as you suggest given the cost of PE and formvar.

Never thought about winding the bare poles with tape - excellent tip! I likely will do a light potting - I actually enjoy pickups to be a bit microphonic but preserving the fiber is a really good point.

This is the 3rd set of pickups I've wound and I must say I always enjoy the results. I would like to get into making my own flatwork and more customized designs - costs are high right now (I live in Canada and I pay anywhere to 30-40% more for materials and shipping costs are murder).

Do you have anything to recommend to measure inductance? Do you find it useful if you do or do winds tell you what you need to know?

Re: Winding your own jm pickups?

Posted: Sat Jan 16, 2021 8:53 pm
by BrendanP
The first set of pups I ever wound were for my Jazzmaster. 42g Electrosol with 8500 winds on the neck, 9100 at the bridge. Light potting, 7.59k neck, 8.17k bridge. It's been gone a few years, but I was really happy with the results. I used A5 at both ends. I like using A2 in bridge pickups, sometimes just on the treble side. I'm using A2 in my Jag with A5 in the neck right now.

I use tape sometimes, but I've also dropped the bobbins into a small container of polyurethane and let them dry overnight.