What's the skinny on the EB-O...

[Wired]

Does anyone have any info on the Gibson EBO bass pickups of the early 70's? I've played a few of these basses and I'd like to recreate their pickups. Are they a twin coil side-winder? Alnico 5's? 8 or 4 slugs per bobbin? what about the wire guage and turns?

Would love any info...

Cheers!

[Spence]

two coils mounted with a plate between the two bobbin centres. Bar magnets either side. 44AWG. Pole shoe between coils screwed to central plate with four screws that then double as pole screws.

[David Schwab]

I posted some pictures of one at this post:

http://music-electronics-forum.com/s...6&postcount=14

This pickup was from a 1974 EB-2. It uses two ceramic bar magnets, and each coil was wound to about 12K with 42 gauge wire.

I unwound about half the wire on each bobbin to bring the total to about 12K to clean it up a little.

[rocket]

What is inside the coil? an iron bar?
The Thunderbird PUs have the magnets inside the coils, right?

[David Schwab]

What is inside the coil? an iron bar?

It's a sheet of steel. It's not very thick. About 1/16". You can see it in the third photo. The magnet is attached to the upper surface of it. It goes right through both bobbins, and has holes in the middle for the screw poles, which are threaded through a keeper bar on top of the thin sheet.

The Thunderbird PUs have the magnets inside the coils, right?

I have some pictures of an original Thunderbird pickup in the same thread. The bar magnet is in-between both bobbins, where the screw poles and keeper bar are in the EB-0 pickup.

Here's the 1974 patent for the Thunderbird pickups (3,902,394).

Bill Lawrence claims in the patent that "...the pole pieces are magnetically neutral and are thus not loaded magnetically but serve merely as inductors"

Hmmmm... interesting. It's obviously a variation on the original Sidewinder. The Gibson Ripper pickups were just smaller versions of the EB pickups, with far fewer turns of wire.

I have no idea what's in the TB Plus pickups, or how far Gibson strayed from the original design. Here's the basic layout as seen in the patent, as well as a top view of an original TB pickup.

[Wired]

Thanks for the info guys. I got my hands on some Korean reproductions a few months ago. Thought there was something wrong when they read 1.2k DC! I guess they are wound with 30 guage wire or something weird. The pickups sounded great, but were very poorly made and had terrible string to string balance. I messed with one and got it fairly even and actually used it in a bass, but its inspired me to make a few from scratch...

[rocket]

I have to admit, I don't quite understand how the thunderbird pu works.

Will there really be a modulated magnetic fields inside the coils? After all the modulated magnetic field creats the voltage.

Also regarding the EB0 I am not sure if this configuration gives very much output, compared to the number of windings.

[Joe Gwinn]

I have to admit, I don't quite understand how the thunderbird pu works.

Will there really be a modulated magnetic fields inside the coils? After all the modulated magnetic field creats the voltage.

Yes, it will work. And we have lots of field reports to prove it.

So, how does it work? Because steel has one thousandth the resistance to the passage of magnetic flux of non-ferromagnetic materials (air, plastic, forbon, brass, most stainless steels, etc), it doesn't take much steel to significantly affect the magnetic field surrounding (and thus passing through) a magnet.

[David Schwab]

Will there really be a modulated magnetic fields inside the coils? After all the modulated magnetic field creats the voltage.

As Joe pointed out, lines of flux want to follow the path of least resistance, so they will flow through the steel cores. Bill Lawrence has also made pickup with no cores (air cores), for acoustic guitars.

Also regarding the EB0 I am not sure if this configuration gives very much output, compared to the number of windings.

The idea of the huge amount of windings was to limit the high frequency response, and and lower the resonant peak. I have read that they were trying to get a pipe organ pedal tone... lots of fundamental. And it worked!

My own experiments with unwinding wire from one of these shows that the output stayed pretty much the same, but it had a much more open tone.

Also, as Joe points out, there are lots of field reports about this style of pickup.. the Gibson Ripper used a variation of the Sidewinder, just smaler and with less windings. Also the pole piece screws were the small mini humbucker screws. These had good output.

Another variation are the original Bill Lawrence Strat size "small humbuckers" that had the single blade up the center. They are made the same way, except instead of the screw poles and keeper, they have a steel blade. The magnetic circuit looks like an inverted T.

[Wired]

The magnetic circuit looks like an inverted T.

So the "like" magnetic poles point inwardly towards the plate and one another...?

[David Schwab]

So the "like" magnetic poles point inwardly towards the plate and one another...?

Yes.

Here's another variation, the Gibson Ripper (patent 3916751) pickup. Imagine this without the screw poles. This is also very similar to the EB-0 sidewinder.

[Wired]

Thanks David, I really appreciate the info...