Blade Style Pickup - Ceramic Magnet Orientation

[rjb]

First, I tried the Mojotone bobbins, but when I potted them with my acetone-cut epoxy...
...they melted!

But... didn't we tell you to use wax....

I once did some goofy experiments with a pair of (ABS) DiMarzio Model P bobbins- got them covered in adhesives and schmutz... so I soaked them overnight in a jar of lighter fluid (naphtha). Except, evidently, I actually used nail polish remover (acetone). I think I was in denial for a few years. I posted pics in another thread- but, thankfully, they got lost in a server crash.

[Freekmagnet]

But... didn't we tell you to use wax....

I once did some goofy experiments with a pair of (ABS) DiMarzio Model P bobbins- got them covered in adhesives and schmutz... so I soaked them overnight in a jar of lighter fluid (naphtha). Except, evidently, I actually used nail polish remover (acetone). I think I was in denial for a few years. I posted pics in another thread- but, thankfully, they got lost in a server crash.

That's a funny story.

Yeah, I suppose you did tell me to use wax. Honestly, I don't feel like going to WalMart to look for a rice cooker to heat the wax. Besides, I don't have room for one on my workbench.

I've wound and potted hundreds of those EMG 35 bobbins.
Never tore one up.
However, I do wax potting, at 140F.
Maybe you just like to make bobbins?
T

Yeah, I'm sure you haven't had any problems at all with those bobbins. Unless you're me, they're pretty much foolproof and you can't beat them as far as price and convenience is concerned. I guess I'm just determined to do things the hard way.

You should have seen me trying to stuff those bobbins into the cover as they were literally falling apart in my hands! I think I broke one of the wires in my haste, because the pickups were DOA.

I actually don't mind making the bobbins at all. It's pretty easy for me and I can make them any size I want. I print the templates out and mount them to the material before I cut it. Cuts with an Xacto knife.

The epoxy works, actually. I cut open a few winds to retrieve the magnets, and the coils were pretty much solid all the way through. It really penetrates, however I'm finding that I have to use more of the epoxy for these heavier winds. The mess is non-existent to minimal. I work on a peice of wax paper. The epoxy doesn't stick to it at all.

[rjb]

So, how thick is that Bristol Board? And the weight of the Epson presentation paper?
Just wondering, la, la, la, la.

[Freekmagnet]

So, how thick is that Bristol Board? And the weight of the Epson presentation paper?
Just wondering, la, la, la, la.

The Bristol mics out at .021". The Epson is .009".

[rjb]

The Bristol mics out at .021".

I'm impressed.
That's quite a bit thinner than "traditional" flat work or plastic bobbin flanges.
And I don't see much, if any, end flaring.
(Then again, I'm easily impressed. And not a "real" pickup winder.)

The Epson is .009".

Irrelevant comparison: That's about the same thickness as a "tin" spice can.

[Freekmagnet]

I'm impressed.
That's quite a bit thinner than "traditional" flat work or plastic bobbin flanges.
And I don't see much, if any, end flaring.
(Then again, I'm easily impressed. And not a "real" pickup winder.)


Irrelevant comparison: That's about the same thickness as a "tin" spice can.

Thanks. Glad you like it.

I figured that the thin material would be good for maximizing the winding area.

Let it be known that these bobbins will flare if you're not careful. The ones I posted were my best ones and I definitely have had a few missteps along the way. I'm still dialing in the optimum settings and refining my technique. I don't know how these'll fare say 20 years down the line, however once finalized, I'm planning to encapsulate them in epoxy, so I figure they'll be safe and secure. That being said, all of the materials are ph neutral materials, so they'll never fade or turn yellow!



"tin" spice can?

[rjb]

"tin" spice can?

You know, like a paprika or dry mustard container.
They are called tins, even though they're made of steel.
Nowadays, most spices come in plastic jars.
Once upon a time, most spices came in "tin" cans or boxes.
They made handy small project boxes.
This was in the Dark Ages, before Altoids.

But anyways, I've found that most "tin" (actually steel) cans - whether for spices, pork & beans, or mineral spirits, are about 9-10 mils thick.
It's just a personal reference- like .1" is the spacing between the legs on old IC "bug".
/

[rjb]

Warning: I have no experience with ceramic blade pickups.
Take the following as "wondering out loud", not as advise.

I'm getting a lot of finger noise.

Are you talking about noise from touching the blades?

I've learned here that is usually capacitively coupled noise that can be cured by grounding electrically conductive poles. But does this help if the poles are non-conductive ceramic magnets?

Also, you can reduce capacitive coupling by increasing the distance between conductive parts- e.g. increase the distance between a steel blade and its coil by wrapping the blade in several layers of tape. But is this relevant for ceramic blades?

I'm thinking that maybe they're a little microphonic.

Quick overview of how a pickup works: Permanent magnet magnetizes a section of the string; thus, vibrating string becomes a "moving magnet" which is sensed by the coil, Faraday's Law, yadda yadda.*

Now let's look at that "steel inductance bar". If there is any space between the magnetic blades and the bar, the bar is magnetized in a manner just like the string. So the bar is sitting there like a big microphone diaphragm; if there is any relative motion between the bar and the coils, it will be detected in the same way the vibrating string is detected.*

I reckon the cure would be to pot the entire pickup, to damp motion of the inductance bar. That would be an argument for wax potting. If you try potting with wax and it doesn't solve your problem, you can melt the wax and try something else. If you try potting with epoxy and it doesn't solve your problem, you have to build another pickup.



* Awaiting correction/elucidation by resident tech editor.

[salvarsan]

The eddy currents depend on the conductivity of the material in question.
More conductivity == more eddy currents == more high frequency attenuation
'More' is a matter of taste, one that your buyers rely upon.

Joe Barden mentioned his 'Satori' moment as when he understood that the electrical circuit should approximate the magnetic circuit.

Then, he made an electrical connection between the steel blades and thus was born approval from Danny Gatton (may God rest his soul and laud his guitar work) and very popular Barden blades for the Telecaster.

Were it possible to plate copper or nickel across a ceramic magnet (and it is, at cost), I'm sure that yet another excellent pickup could be built and sold.

-drh

PS. God, in pensive 2am moments, listens to Danny Gatton playing "Harlem Nocturne" (drh)

EDIT: Is it possible that you could build an Alnico 8 equivalent? The conductivity issues go away although its field is stronger.

[Freekmagnet]

You guys raise some really excellent points here, and I'll try to address them specifically.

Are you talking about noise from touching the blades?

Now let's look at that "steel inductance bar". If there is any space between the magnetic blades and the bar, the bar is magnetized in a manner just like the string. So the bar is sitting there like a big microphone diaphragm; if there is any relative motion between the bar and the coils, it will be detected in the same way the vibrating string is detected.*

I was talking about fretting noise. I actually have a really dead set of flats on the bass now, and to get that much fret noise on old flats was interesting. Your theory makes sense - the bar is stuck directly to the poles with nothing between them. I suppose it's possible that the bar could still be moving - maybe potting the bar as well would be a good idea.

Incidentally, I did re-install the pickup after adding more potting material and the finger noise went away.

That would be an argument for wax potting. If you try potting with wax and it doesn't solve your problem, you can melt the wax and try something else. If you try potting with epoxy and it doesn't solve your problem, you have to build another pickup.

You are right about this as well. Perhaps I should consider doing a trial run with wax before committing to epoxy encapsulation. The stuff I'm using for the coil never completely dries - it stays kind of gummy for some time.

The eddy currents depend on the conductivity of the material in question.
More conductivity == more eddy currents == more high frequency attenuation
'More' is a matter of taste, one that your buyers rely upon.

During one round of winds, I realized that I'd forgotten to put the bar on the bottom of the pickup. Once I plugged it in, I could tell right away that the pickup was different. The steel bar seems to "spread" the highs out in such away that they seemed more evenly distributed. Without it the, pickup was more mid-focused. Not a bad or good thing - just different sounds.

EDIT: Is it possible that you could build an Alnico 8 equivalent? The conductivity issues go away although its field is stronger.

It's funny you mention that - I did happen to wind a couple of coils with A5 magnets. The magnets are narrower and the bobbins are a little taller, so they're not exactly the same, but I'm sure they're within the same ballpark. I plan to drop them in there to try them out at some point, but I'm kind of a "one thing at a time" kinda guy.

Overall, this pickup is sounding really great to me right now. I had it in the bass for about a week and I've been liking it more and more. It's really fat and really clear. The attack is crazily immediate and there's plenty enough midrange to coax a more "classic" sound out of it. I've never been acquainted much with ceramic pickups - I've always kind of assumed that they were of lesser quality sound-wise for probably the same reasons most other neophytes believe that ceramic is inherently inferior to Alnico. That the fact is that a ceramic pickup can sound warm and funky just as well as any other magnet. It just depends on what type of sound you're going for and how you design the pickup. Originally, I chose ceramic because I was using that Peavey pickup as a springboard for my own design. Turns out I made something else that I happen to like.

[Mike Sulzer]

Then, he made an elecrical connection between the steel blades and thus was born approval from Danny Gatton (may God rest his soul and laud his guitar work) and very popular Barden blades for the Telecaster.

Where were the connections made? A connection at each end would give the the most effect from eddy currents since the loop would enclose the most possible flux. On the other, hand a single connection would give the least, hardly any at all since there would be no path including significantly more flux than with no connection.

[salvarsan]

Where were the connections made? A connection at each end would give the the most effect from eddy currents since the loop would enclose the most possible flux. On the other, hand a single connection would give the least, hardly any at all since there would be no path including significantly more flux than with no connection.

We had this discussion 6 or 7 years ago on Ampage.
At greater length.

Don't take my word for it on Barden blades.
Ask a vendor if they'll let you look at a Barden T-style so you can draw your own conclusions.

[John Kolbeck]

I have a set of Danny Gatton T-Styles, they look like this underneath

[rjb]

I have a set of Danny Gatton T-Styles, they look like this underneath

What I think I see is a strip of copper tape over a ceramic magnet, bridging two steel blades.
A bare drain wire is soldered to the tape, thereby grounding the blades.

I've done the same thing, e.g. with a pair of HBs I made to replace those in my Peavey T60.
(One had died, presumably because the epoxy potting shrank, tearing the coil wire- that's one populist theory).
I'm sure lots of folks do the same thing.
Was this, in its time, considered a profound discovery?
(I wouldn't be surprised. In it's time, "After all, tomorrow is another day" was considered a profound statement.)
Que music.

All I'm saying in my snarky way is that things we take for granted may not always have been obvious.

[Mike Sulzer]

I have a set of Danny Gatton T-Styles, they look like this underneath

Thanks. Can't be sure, but it looks as though there would be a single connection between the blades where the shield fastens. The thing about blades is that there is a path for eddy currents around the entire blade. The blade is usually kept thin, certainly to take up less space in a humbucker designed to fit a single coil slot, but also to keep the eddy currents down. A path around both blades would probably attenuate the highs too much. Of course, if you are going to ground the blades, you by default connect them together. So what I see here is a convenient mechanical connection to minimize hum from electric fields.