Pickup transplant

CPike · #1 06-15-2011, 08:23 AM

I'm thinking about transplanting pickups from one bass to another. The source bass pickups are Ibanez "soap bar" types for 5 string. The destination bass is a hot rodded 4 string fretless. Is this possible, or is the fact that they're originally for 5 strings preclude this as an option?

.cdp

mikezimmerman · #2 06-15-2011, 08:46 AM

It depends on the coil structure of the pickup. If it's a dual-coil humbicker with both coils going all the way across, there's no problem. But if it's a split-coil with one coil handling half of strings and the other coil handling the other half (or 3 and 2, for a 5-string pickup), then the split between the two coils might fall right under one of the strings if you install it on a bass with a different string count.

ctmullins · #3 06-15-2011, 08:54 AM

I respectfully disagree, Mike - the string sensing is a product of the magnetic field, not the coil structure. So if you have a string that's between the two coils, but within the magnetic field, then its vibrations should be picked up by the magnets on either side, which would induce voltage in the coils on either side.

But I've been wrong before...

CPike · #4 06-15-2011, 09:09 AM

How can I discern the coil structure? The pickups appear permanently sealed. The bass they came from is an Ibanez Roadstar II RB885, and the specs show the pickups to both be "LO-B5". The specs from the 4 string version of this bass (RB999) show pickups to be "LO-B" and "LO-BS". Does this shed any light on the subject?

.cdp

mikezimmerman · #5 06-15-2011, 09:34 AM

ct -- You may well be right, that the magnetic field could sense the string even without the coil directly beneath it. I'm just saying that it might be a problem, as well--I suspect it depends on the individual pickup.

.cdp -- I don't know much about the construction of those old Ibby pickups, though some of the Ibanez experts here might. You used to be able to get magnetic paper from EMG that would show the coil structure. I don't see it in their shop anymore, but maybe some other pickup/builder supplier has it?

SGD Lutherie · #6 06-15-2011, 02:37 PM

Quote:

Originally Posted by ctmullins

I respectfully disagree, Mike - the string sensing is a product of the magnetic field, not the coil structure. So if you have a string that's between the two coils, but within the magnetic field, then its vibrations should be picked up by the magnets on either side, which would induce voltage in the coils on either side.

But I've been wrong before...

Mike is right. He said split coils would be a problem. He is right. On a split coil pickup you have two coils with the magnets in them. Think of a P bass. Each coil covers two strings.

Now what if you tried to use a 4 string P bass pickup on a 5 string? Your D string wouldn't make too much sound! The reason is it's between the two coils and oppositely phased magnets.

The same thing can happen on a 4 string using a 5 string pickup. If the pickup is not a dual coil humbucker, you might have a dead spot under a string.

Another issue is that if the 5 string pickup uses a pole or magnet for each string, they are not going to pick the 4 strings up evenly. Since the poles and strings will not line up.

The only way this will work is if the 5 string soapbars have blade pole pieces and are not split coils.

SGD Lutherie · #7 06-15-2011, 02:40 PM

Quote:

Originally Posted by CPike

How can I discern the coil structure? The pickups appear permanently sealed. The bass they came from is an Ibanez Roadstar II RB885, and the specs show the pickups to both be "LO-B5". The specs from the 4 string version of this bass (RB999) show pickups to be "LO-B" and "LO-BS". Does this shed any light on the subject?

.cdp

If you had some magnetic viewing paper, that wold give you an idea where the magnets/poles are.

You can also try and drag a magnet past the front of the pickups and feel how it's pulling or pushing.

Another thing to try is to take a zip lock sandwitch bag and put some iron or steel filings in it. Then close it tightly and put it on top of the pickup. The filings will stand up and show where the magnets are.

ctmullins · #8 06-15-2011, 02:41 PM

I completely defer to your expertise, David. So it sounds like the problem is actually the "oppositely phased magnets", as you mention. In other words, the top coil would pick up some vibration, and the bottom coil would as well, but they would tend to cancel each other out, right?

SGD Lutherie · #9 06-15-2011, 02:48 PM

Quote:

Originally Posted by ctmullins

I completely defer to your expertise, David. So it sounds like the problem is actually the "oppositely phased magnets", as you mention. In other words, the top coil would pick up some vibration, and the bottom coil would as well, but they would tend to cancel each other out, right?

With a split coil pickup, like a P bass, they have the two coils of the humbucker positioned in an offset fashion. The two coils are wired out of phase but have opposite polarity magnets to make them back in phase.

If a string is positioned between, and not over the coils, it wont get picked up. The reasons are; it's between the coils, and not over them or a pole piece, and it's between the N and the S poles of the magnets. There's a dead spot there.

That's why split coil pickups are not as popular on guitar. They sound like single coils, but if you bend a string across them it losses sound as it passes from one to the other.

CPike · #10 06-15-2011, 03:52 PM

Thanks to all the suggestions! I'll try to test them by one of those methods. I just wanted to be sure before I go routing new channels and whatnot...

.cdp

CPike · #11 06-15-2011, 11:03 PM

Update: I took one of those super-strong, nickel-plated neodymium magnets and placed it on the soap-bar pickups. It attached itself, and I was able to move it across the entire length of the bar (diagonally, actually) smoothly, without any interruption. There was no push or pull that would indicate separate poles for each string. I suppose now it's safe to assume there is a single blade pole piece inside?

.cdp

SGD Lutherie · #12 06-16-2011, 12:09 AM

Sounds like a single bar.

Be careful in the future. If that pickup has alnico and maybe even ceramic magnets, the neodymium magnet can demagnetize them and ruin the pickup! I'm guessing it had ceramic magnets, which are pretty hard to demagnetize.

In general keep neo magnets away from other magnets.

To play it safe, I would remove the soapbar pickup, hook it up to a cable so you can plug it into an amp, and hold it upside down facing the string on the bass you want to install it into. If you get an even response across strings then you are probably OK. If some sound weak, I would pass on using that on a 4 string bass. You can even pluck one string and move the pickup back and forth and see if you hear a dropout.

CPike · #13 06-16-2011, 12:29 AM

Thanks for the warning - the neo magnet I used was one of those tiny 1/2cm cubes you get for bulletin boards and refrigerators.

This is all just a "what if" kind of a mod project. The Frankenbass sounds great as is, but my unofficial motto is, "If it ain't broke, break it and try to make it better." Now that I know they're likely to work for a 4 string, I need to decide whether or not I want to go to the trouble of re-routing the body cavities and wiring and yadda yadda. I kinda had hoped the fiver soap bars were unsuitable for the four, so I could just forget about the whole dang thing, but noooooooo...

.cdp