simple P-90 Question?

[Robbie95]

I want to create a humbucker sized single coil using the P-90 bobbin. What all needs to be done to get the bobbin to fit inside a humbucker cover?

[cenizasblancas]

Hi.here are some information:

http://music-electronics-forum.com/t3113/

When i get home i´m going to give you more info, i hope this can help.

Regards

Juan Motta

[Robbie95]

How could I make my own bobbin? I've seen blank pieces of flat work for making strat style single coils. Could they be used to make one more suited to this project?

Note that I'm not really aiming for a P-90 sound, not exactly anyway. I simply want a fat single coil that fits snug in a humbucker shell.

[big_teee]

How could I make my own bobbin? I've seen blank pieces of flat work for making strat style single coils. Could they be used to make one more suited to this project?

Note that I'm not really aiming for a P-90 sound, not exactly anyway. I simply want a fat single coil that fits snug in a humbucker shell.

You use a regular P-90 Bobbin, and cut some off of each end.
Center the cut off bobbin on a regular bucker base plate.
You will have to drill 8 new holes to hold the bobbin and the 6 Fillister Screws.
You won't get as much wire on the short bobbin so you will need to use 43, or 44 Gauge.
You will need a keeper bar under the bobbin and the 2 magnets same polarity just like a real P-90.
That will get you the pickup.
Your on your Own, as far as the way you cover it.
Good Luck,
T

[Possum]

You have to make your own bobbins, buy Jason Lollar's book and learn how to do that. The problem you are going to run smack into is that the end result isn't going to sound like a P90. To get enough wire on the bobbin you have to make the coil TALL, which makes it brighter. P90's signature tones come from the use of 42 PE wire and a wide flat, low profile coil. You can use thinner wire and right away you lose transparency and quack that P90's have. You should build one anyway for the experience and to learn about what radically different coil designs do to tone. I had about four different versions of that idea back when I started, none of them really did what I wanted, and were too slow to build commercially, so eventually I quit selling all of them. I did come up with a really nice sounding single coil in a bucker size eventually, using a pretty out of the box idea and it has alot of P90 qualities, but its not a P90. You can see it on YouTube, I called it a Pig-90. Gibson and Duncan have products, but they sound like steel pole strat pickups with thin wire.

[copperheadroads]

You have to cut off anywhere from 3/16" to 1/4" off each end of a standard p-90 bobbin depending on the cover you choose to use .
& really your not gonna get a ton of 42 gauge wire on there so thats why most use 43

[JGundry]

If you are good with a bridge pickup at 8K or lower then you can do a humbucking cavity 42AWG P-90. I had the parts made for these including a tin plated brass baseplate with dimples like a vintage baseplate. I also stamped Nickel covers. But you cannot expect them to sound like a soap bar P-90 that with the baseplate solidly against the pickup cavity. Instead you have a floating pickup and when you include the nickel cover the tone in a Les Paul leans a bit closer towards the tone of P-90's in an Epiphone Casino. Still a cool tone.

I have been working on tooling for metal and plastic P-90 parts for about a year now. I have a bunch of vintage P-90's I have been testing and personally about 7.8K in the bridge and even lower still is what I prefer for a bridge P-90. I think people expect P-90's to be much higher in ohms but the lower resistance makes for a versatile mid 50's spec. pickup. So from that standpoint 42 awg can be done in a humbucker cavity if you are machine winding as P-90's were.

[Possum]

They still come out sounding like something else besides a P90 and just too bright for me, I made those things years ago and whlle they were superior to the commercial stuff, they never got much sales like the Pig90's do which sell really well with zero customer complaints. I managed to get about 8K of 42 into in the ones I built, but a tall coil is just too biting; I never claimed they were P90's in a bucker cover because technically its not true, a single coil in a bucker is just a single coil in a bucker cover. One version I made was based on what I learned from the Kay Kleenex box pickups, those are vastly different than regular P90s with some good design lessons inside the cover. Those were real unique sounding, but also at that time you couldn't get undrilled bucker covers and I got tired of gluing plastic bobbins onto baseplates, its just not a real good idea. Overall as a product idea there's not much market for them. Still, you should get Lollar's book and learn those skills so you can design your own pickups from scratch. Pickup Winding Book

[Possum]

This is a hard to find demo of the product I designed, these replaced all the earlier attempts, nothing P90 about them but you do get some of that vibe:
1944 Epiphone Electar and Gibson ES 335 dot reissue with Stephens Design Pig 90 pickups - YouTube

[Mike Sulzer]

They still come out sounding like something else besides a P90 and just too bright for me,

If the sawed off coil, or whatever, is too bright, then one should figure out why and do something about it. This is a matter of the circuit properties of the pickup, and perhaps other things, but the circuit properties one can change in this case. Since there are not enough turns, the resonant frequency is too high, given the normal cable capacitance. Therefore add a few hundred pf across the coil to lower it. The Q will probably be too high, so add a few hundred K in parallel. Play with both values until you like what you hear. It is still not a P90 because at the very least, the signal level is a bit low. But it is better than leaving the resonant frequency and the Q too high.

[Possum]

The problem with cutting up a P90 bobbin and putting it in a humbucker sized space is that it leaves you with very little room for the end of the coil, thats where the restriction for coil size lies, so you can't get much wire on that bobbin because the ends of the coil hit the cover with too few turns. So, you have to build your own bobbin and go UP in size, making a tall bobbin, so you're stuck making bright sounding coils because its a tall coil. You kind of have to look at this as other than fitting a P90 into a bucker cover, and turn it into, how can I make a good sounding warm single coil pickup in a bucker housing? So, throw away the P90 design and start from scratch.

Here's another clip of the pickups I designed, the other video sounds dark, because jump blues guys typically always turn their tone knobs back alot, this is a better look at my solution; note that the pickups are NOT out of phase, they just have a unique kind of sound that way. The amp is a vintage Magnatone 2x12" model:
http://www.youtube.com/watch?v=03BI5A_qxh8

[Mike Sulzer]

so you're stuck making bright sounding coils because its a tall coil.

Compared to a P90, humbucker coils are tall. All humbuckers are not bright. I do not think it is true that all tall coils are bright.

[marku52]

Mike et al, check out this thought experiment, and tell me if I am all wet.

We have a rod magnet, typical alnico, long and thin, that we are going to wind N turns on. We choose two aspect ratios for the bobbin. One lies along the full length of the magnet, the other is occupies only a small portion of the rod's length, and extends outwards like an asteroid belt.

I hope you get my word pictures, I am creating two coils with as different aspect ratios as possible, but using the same N turns.

Now visualize the magnetic field lines around the magnet. They are concentrated next the surface of the rod, and reduce in intensity as the radial distance from the rod. When stimulated the output of the coil is the summation of the voltages induced in each turn. This implies that the turns next to the magnet have higher induced voltage than the ones farther away (as they have more lines of force cutting them)

So the bobbin with the turns laid all along the magnets length will have a higher output (more of its turns are cut by the higher intensity lines of force next to the magnet.

And here is the key thought: To the voltage induced in the turns right next to the magnet, the outer-lying coils look like an RLC filter, rolling off the highs from the center windings that produce most of the output voltage.

Hence Marku's Theorem: Given identical turns and magnets, a tall thin coil will sound louder and brighter than a short wide coil.

Ergo hoc
Dicto simpliciter
Klaatu barada nikto

[Mike Sulzer]

The string gets magnetized by the permanent magnet. The magnetic field lines from this magnet go down through the coil and return to the string. (They are always closed loops.) When the string vibrates the field through each loops changes, and we say that there is a change in time of the flux through each loop. This induces a voltage in each loop. The voltage induced in the loop is proportional to the rate of change of flux; that means all the flux enclosed by the loop.

Now let's consider the field lines going down from the string. The field lines indicate the direction of the field; the strength depends on how far apart they are. If the string moves towards the coil, the number of field lines enclosed by the loop increases since the field lines are closer together closer to the string. It is not true that a bigger loop contains less total flux (as long as we just consider the lines going down).

There is an effect such as you say, but it involves as well the flux going back up, which points in the opposite direction. A really big loop that contains nearly all the flux going back up as well as that going down has very little net flux through it, and there is very little change with string motion. There may be some of that effect in a P90; you would have to model the field from the string. But I think that this is not such a big effect.

Taller coils can be brighter, for example, because the inductance can be less. But I do not think you can say that a taller coil is always brighter than a flatter one.

Mike et al, check out this thought experiment, and tell me if I am all wet.

We have a rod magnet, typical alnico, long and thin, that we are going to wind N turns on. We choose two aspect ratios for the bobbin. One lies along the full length of the magnet, the other is occupies only a small portion of the rod's length, and extends outwards like an asteroid belt.

I hope you get my word pictures, I am creating two coils with as different aspect ratios as possible, but using the same N turns.

Now visualize the magnetic field lines around the magnet. They are concentrated next the surface of the rod, and reduce in intensity as the radial distance from the rod. When stimulated the output of the coil is the summation of the voltages induced in each turn. This implies that the turns next to the magnet have higher induced voltage than the ones farther away (as they have more lines of force cutting them)

So the bobbin with the turns laid all along the magnets length will have a higher output (more of its turns are cut by the higher intensity lines of force next to the magnet.

And here is the key thought: To the voltage induced in the turns right next to the magnet, the outer-lying coils look like an RLC filter, rolling off the highs from the center windings that produce most of the output voltage.

Hence Marku's Theorem: Given identical turns and magnets, a tall thin coil will sound louder and brighter than a short wide coil.

Ergo hoc
Dicto simpliciter
Klaatu barada nikto

[Arthur Dent]

I'm convinced the reason taller coils tend to be brighter is not entirely due to there being less inductance. I've noticed the same effect in coils with fewer than 500 turns, where the inductance should be low enough to be inconsequential. Taller, thinner coils still tend to be much brighter than shorter, fatter coils. Of course it's still just a tendency, not a rule.