Blade Style Pickup - Ceramic Magnet Orientation

[rjb]

Looking at the mass of steel and the size of the magnet required I'm going to estimate that these monsters had very low turns or they would have sounded abysmal. That said there is enough room on the coils pictured above to put a lot of wire. Perhaps they were wound with 40AWG? I'd start with 3000-4000 turns and see what that sounds like in series/parallel before going any further.

3750 winds of #42.
Unless that was only for toasters, in which case blades might be something else.
http://music-electronics-forum.com/t13530/

FWIW, according to an assembly diagram provided by Chip Todd, official specs for T-60 (guitar) blades are:
.859" x 2.491" x .062"
Material: Low Carbon, Mild Steel
Deburr Completely
Plate: Copper Flash, Nickel Plate, Chrome Plate

.062" = 1/16" = a bit thicker than 16 GA (maybe .062" is with the plating?)
I imagine the T-40 used the same thickness blades.

(My T-60 blades, which don't match any documented version, are .615" x 2.273 x .075" = 14 GA, bare steel)

If I were the OP, I think I would take T's advice and either build or buy a pair of "normal sized" (whatever that may mean) dual blade pickups.

[Freekmagnet]

Yes, I'm building the bass version of the pickup. Sorry I didn't clarify. I didn't mean to cause any confusion.

Here's the info I do have. I've gathered this info from I various forums, including this one.


“... The original pickups had two magnets; one through each of the coil's bobbins. These magnets were ferrite material and were rectangular in cross-section and were stood on edge. There was a magnetic return strip of iron laid flat across the bottom of the pickup and magnetically attached to the bottom edges of the pickups. This iron kept the magnetic field from forming on the bottom of the pickup identical to the top field, so the field on the topside was greater than of that of the pickups like Gibson, (without magnetic returns). We used iron, as opposed to steel, as iron is more compatible with magnetism than steel. Steel won't remain magnetized as long as iron.

The blade type pickup had two thin strips of plated iron arranged on edge through the bobbins, (which had to be redesigned with a thinner slot through the centers). The magnet was quite like the magnets of the early pickups and was held between the two blades. The magnet was laid flat, (not on edge), and took the position of the earlier magnetic return. We found the position of the magnet was more efficient, so only one magnet was used, with the overall result a stronger and better-shaped magnetic field around the strings. ... ”

"R.T. Lowe, the pickup's creator, reports that each coil is 3750 winds of #42."

Dimensions measure from an actual PU:

L x W x H (or thickness)

Bobbin: 3.16" x .96" x .45"

Wire Channel: 2.54" x .257" x .375"

Blade: 2.5" x .65" x .125"

Magnet: 2.5" x .8" x .189"

Bobbin thickness, top and bottom: .04"

Some photos someone sent to me:



As far as being insane for doing this, I won't dispute that. My initial rationale for starting this project was this: I recently started building basses. Every time it comes to specing the pickup my choices are:

P Pickup.
J Pickup.
MM Pickup.
Some ugly block of featureless black plastic designed to go into an active bass that I'm not building.

There's some other fairly pricey pickups out there for Rics or Gretsch or even T-Birds - none of which are basses that I'm in love with sound-wise. We'll, T-Birds sound cool. P's, J's and MM's I already have. Besides, I can just buy a Fender-style pickup for a few bucks. Why would I build one of those?

I really like the sound of the T-40 / T-45, but they are a nightmare to play. Used pickups in working order are getting harder to come by and they're getting more and more expensive. Besides, the pickup looks really cool.

And (maybe because I have no metal-working skills) I would find the cover and baseplate a bigger challenge than the bobbin- and would work on those first, not as an afterthought.

On winding skills:
If my sample of two T-60 pickups is any indication, lack of winding skill may be a plus in capturing Peavey "mojo".
Mine had coil wire flying out beyond the bobbin flanges, all encapsulated in black epoxy.

On mounting the pickup to the baseplate:
The trick is not to mount the pickup to the baseplate.

With magnetic blade "toaster" models, the bobbins were dropped into a plastic tub, which was then filled with epoxy. The tub was inserted in the cover, a strip of rubber tape placed over the back, and the baseplate soldered to the cover.

On potting:
I would avoid yucky epoxy at all costs. It makes repair nearly impossible, and some folks suspect it shrinks over time- tugging the coil wire and killing the pickup. Use wax.

ymmv,
-rb

PS - If you search T60 on this forum, you'll find several threads that may be helpful.

Thanks for all the tips. Oddly enough, the one thing I actually do know how to do in the above list would be to make the PU cover. I worked in a metal shop for years, and I could probably solder one together out of sheet stock without too much trouble. I've worked with molds and stuff before, so that should be doable.

I bought Jason Lollar's book and built the winder. Seems to be working OK.

This may be going against the grain, but I've always believed that a nice, bright and clear tone makes your bass sound great. A thick and dark tone makes the band sound great. I run by treble and mids flat and boost my bass. I always play flats.

I'll build them and see how they sound. If they sound great, that's awesome. If I build these and they suck, I'll try something else. I'm going to buy a beater and route a swimming pool and use it as a mule.

And really, thank you guys for your input.

[big_teee]

You're not crazy at all, and I bet you will do fine.
You just started with a harder project, but that is fine.
Electrically a very similar pickup is the EMG soapbar.
It's the black blob you were talking about.
And It uses the magnets in the bobbins like you mentioned.
You could use those in a home bobbin.
It is these parts.
Ceramic 8 Bar Magnet 2.60" Long
Bobbin
4 String Bass Blade Pickup Bobbin
They come in 4,5, 6, string sizes.
Those are great magnets and bobbins, and I've used a ton of them.
I've modified the magnets and bobbins for different projects.
The magnets as blades will be brighter, & quieter, than the steel blades.
With some cutting and fitting you could use them as a basis to make your T-60 bigger bobbins.

T

[rjb]

Some photos someone sent to me:

Wow. Those remind me of my T-60 pickups- the ones that "don't exist".
Note that they have unplated steel poles and a fragment of a "toaster cover" (which was part of the plastic tub I mentioned).
Later versions had thinner, plated, exposed blades like the image linked to in message #15- and, reportedly, sounded better.
If I were going to go through the trouble of making these, I'd go with thinner blades.

YMMV,
-rb

[Freekmagnet]

You're not crazy at all, and I bet you will do fine.
You just started with a harder project, but that is fine.
Electrically a very similar pickup is the EMG soapbar.
It's the black blob you were talking about.
And It uses the magnets in the bobbins like you mentioned.
You could use those in a home bobbin.
It is these parts.
Ceramic 8 Bar Magnet 2.60" Long
Bobbin
4 String Bass Blade Pickup Bobbin
They come in 4,5, 6, string sizes.
Those are great magnets and bobbins, and I've used a ton of them.
I've modified the magnets and bobbins for different projects.
The magnets as blades will be brighter, & quieter, than the steel blades.
With some cutting and fitting you could use them as a basis to make your T-60 bigger bobbins.

T

Those Ceramic 8 bars might actually work. I could use the steel bar to cross over them. Have you actually cut them down successfully? What do you cut them with?

[Jason Rodgers]

You're doing something very similar to my first pickup attempt.
MIMF ? View topic - Experimental rail pickup construction: wiring question
The next two sets I wound were done with stock Mojo parts, then another scratch build. I have a tendency to want to do things MY way first, heedless of the warnings and advice from those more experienced (i.e., I'm a glutton for learning the hard way...), but I'm glad I tried this first set from scratch. I learned a lot, and they don't sound too bad!

[big_teee]

Those Ceramic 8 bars might actually work. I could use the steel bar to cross over them. Have you actually cut them down successfully? What do you cut them with?

what would you need a steel bar to cross over them for?
The magnets are .200" thick. They may not go in your bobbins.
If you are careful and tape them up good you can grind them down, run the grinder slower.
T

[Freekmagnet]

You're doing something very similar to my first pickup attempt.
MIMF ? View topic - Experimental rail pickup construction: wiring question
The next two sets I wound were done with stock Mojo parts, then another scratch build. I have a tendency to want to do things MY way first, heedless of the warnings and advice from those more experienced (i.e., I'm a glutton for learning the hard way...), but I'm glad I tried this first set from scratch. I learned a lot, and they don't sound too bad!

Yeah, I'm kinda with you there. I really have no idea what I'm doing, but I'm having a good time bungling through it.

And dude, that pearloid covered guitar you posted is SuperBad.

what would you need a steel bar to cross over them for?
The magnets are .200" thick. They may not go in your bobbins.
If you are careful and tape them up good you can grind them down, run the grinder slower.
T

Honestly, I don't know what the steel bar would be for. Supposedly they had them on the original, so it's easy enough to stick it on there and see if it does anything.

I can make another bobbin if necessary - I made routing templates for cutting the flatwork and the slot template I can alter easily. I have plenty of Lexan and it's pretty cheap.

I'm going to try grinding a little piece of magnet down to see how it works. I have some here. I more worried that they're not tall enough. In fact, this magnet measures .125" wide:

Ceramic 8 Bar Magnet 2.625" Long

[Jason Rodgers]

For what you're trying to attempt here (see what I'm doing, giving the advice I wouldn't have taken), don't get hung up on the size of the magnet. big_teee's suggestion to use one magnet on each blade will get you the ceramic quality you want without slowing your progress, or needing to grind magnets.

The biggest take-away I got from my experiment (and David King warned me!) is there really is such thing as too much steel. If the original Peavey pickups had ferrite cores, you've already significantly changed the outcome by using thick steel bars. In my pickups, that Imperial ton of steel caused some serious eddy current action and the result was loss of clarity, string separation, and sparkle on high strings. They work for very chuggy, sludgy, saturated, low-tuned metal, but clear and trebly tones are not in this recipe. Cut your losses (literally) and use the separate magnets and no steel spacer.

[David King]

Ceramic magnets can be cut on a tile saw. You can probably find a cheap one at Harbor Freight or used on Craigslist. If not you can certainly rent one for a day and cut all your magnets at once.
That said your current magnet might work just fine. The steel will redirect the field where it needs to go and you'll hear something.

Regarding your future pickup choices, check out some of the 1980's Japanese HB pickup designs on the Yamaha basses and Ibanez Roadstars. A lipstick tube pickups is another interesting option that looks different and can sound great.

[Freekmagnet]

what would you need a steel bar to cross over them for?
The magnets are .200" thick. They may not go in your bobbins.
If you are careful and tape them up good you can grind them down, run the grinder slower.
T

You're doing something very similar to my first pickup attempt.
MIMF ? View topic - Experimental rail pickup construction: wiring question
The next two sets I wound were done with stock Mojo parts, then another scratch build. I have a tendency to want to do things MY way first, heedless of the warnings and advice from those more experienced (i.e., I'm a glutton for learning the hard way...), but I'm glad I tried this first set from scratch. I learned a lot, and they don't sound too bad!

For what you're trying to attempt here (see what I'm doing, giving the advice I wouldn't have taken), don't get hung up on the size of the magnet. big_teee's suggestion to use one magnet on each blade will get you the ceramic quality you want without slowing your progress, or needing to grind magnets.

The biggest take-away I got from my experiment (and David King warned me!) is there really is such thing as too much steel. If the original Peavey pickups had ferrite cores, you've already significantly changed the outcome by using thick steel bars. In my pickups, that Imperial ton of steel caused some serious eddy current action and the result was loss of clarity, string separation, and sparkle on high strings. They work for very chuggy, sludgy, saturated, low-tuned metal, but clear and trebly tones are not in this recipe. Cut your losses (literally) and use the separate magnets and no steel spacer.

Advice is cool. You guys are starting to make sense to me.

Here's another option that I completely forgot about: I have have some ceramic magnets that will fit in the existing bobbins no prob! They're 2.5" x 0.125" x .5" and they're oriented on the correct side. That'd be about as easy a fix as could be. I think I bought them in the event of Plan A not panning out. Or maybe I was going to A/B the two of them. I don't remember.

Sounds like you guys like the ceramic blades over steel for a number of reasons, namely a brighter, or less muddy, pickup.

It also seems to me like you guys are saying that the return strip is superfluous. Just out of curiosity, is there any reason for a return bar on the Peavey pickup?

[Freekmagnet]

Regarding your future pickup choices, check out some of the 1980's Japanese HB pickup designs on the Yamaha basses and Ibanez Roadstars. A lipstick tube pickups is another interesting option that looks different and can sound great.

I'll take a look at some of those Japanese pickups. I tried some lipsticks on another bass - they sounded alright. They didn't have enough umph in the low end for me. I might build a little preamp for it and see how it goes.

The "looks different" is big seller for me. Lots of chrome. I saw these on ebay, and my jaw dropped...



I thought about buying it, but I figured that the spacing was weird, and I could see that they had a weird mount, and they prolly had no kind of output.

[big_teee]

Ceramic bass humbucker pickups with plastic covers, & no steel are IME about the quietest.
Once you add metal, you get to start fighting little noises.
I also like multi-coil, and split coil Alnico rod magnet designs.
Sidewinder pickups are cool too.
I leave the Single coiil bass pickups to the others.
The cross-over bar you mentioned may be a shield, ground, or maybe to make it sound fatter.
That would depend on what bass era of sound you"re chasing I presume?
T

[Freekmagnet]

Ceramic bass humbucker pickups with plastic covers, & no steel are IME about the quietest.
Once you add metal, you get to start fighting little noises.
I also like multi-coil, and split coil Alnico rod magnet designs.
Sidewinder pickups are cool too.
I leave the Single coiil bass pickups to the others.
The cross-over bar you mentioned may be a shield, ground, or maybe to make it sound fatter.
That would depend on what bass era of sound you"re chasing I presume?
T

That's good to know. I'm still undecided about how to approach the cover at this point.

Those are all cool design concepts.

I'm chasing something that sounds fat and funky. Like, the bark and proud midrange of a P combined with the punch of a 'Ray. I mostly like recordings from the 60s and 70s. I get kinda hazy past 1982.

I have those ceramic bars. I can stick them into a set of those flatwork pieces. I can place the bar on bottom - or not. I'm really not in a hurry to start winding at this point, so if I gotta take more time with my bobbins, that's totally fine with me.

[David King]

Connecting the backs of the magnets with a ferrous bar should improve the field strength on the string side and bump up the volume accordingly. It will also darken the tone which may be what you're after. If you ground it you'll reduce any induced hum.
Some of the best sounding bass pickups out there are the Kent Armstrong pickups in Ken Smith basses. They are a simple design using setscrews for poles and ceramic bar magnets.