Magnets

[Rodney Hamblen]

I just wanted to put a few thoughts on the Forum regarding magnets in guitar pickups. There is a lot of misinformation online that I don't agree with. And maybe my info here will be considered misinformation as well. Cest La vie.

1) Materials - other than making a certain magnetic strength available have no bearing on the sound of your pickup. My modified Z Coils with 1/8" X 1/8" N42 magnets sound just like a sweet set of AlNiCo Strat pickups. The magnetic strength sets the sound, not what the magnet is made of.

2) The "the stronger the better" magnet theory is not correct. Strings have a saturation point where further magnetic field strength makes no change in the (temporary) magnetic strength of a string, this saturation point is above the point where string vibration is negatively impacted by the magnetic field so we never reach this point. We are limited on magnet strength based on whether wolf tones are created at a point on the neck where we intend to play. Wolf tones are more pronounced as we move up the neck because the strings are closer to our pickups. So a strong magnet means we have to keep our pickup set very low in the pickguard to avoid wolf tones, which moves the coil away from the string.

It's better to have a magnet in our pickups that doesn't cause wolf tones until the pickup is as close to the pickup as we'll ever play it, this keeps the coil as close to the string as we can get it and that maximizes our volume from the pickup.

3) "Stronger magnets means more bass" isn't fully correct either. If we want to emphasize bass tones we need to magnetize a longer length of the string. Larger diameter magnets per string, or more magnets per string, or an extended magnetic field (like humbuckers, Z Coils and MFD single coils) magnetize larger portions of the string. The old Seth Lover staple pickup is an interesting application of a string magnet with a rectangular shape. Coil design also matters but we're just talking magnets here.

4) Any pickup using a bar magnet will have a huge magnetic field compared to a magnet per string (Fender single coil pickup) design. These pickups use pole pieces to shape/focus part of the magnetic field underneath the string. Once that's done that magnetic field typically goes back to a baseplate or collector of some sort that returns that magnetic field via stamped metal bits back to the magnet.

5) There is a lot of discussion about Tele bridge pickup backing plates, aluminum shields under Strat pickguards from the 50's, etc about how these components focus the magnetic field and shape the sound. A magnetic field will preferentially flow through metal vs air, but any magnetic circuit that has an air gap will inhibit the magnetic field movement through the circuit. The magnetic field will flow through the path that has the smallest total air gap(s) from the N pole to the S pole of the magnet. Considering a Tele bridge pickup find the closest piece of metal to the any of the string magnets and that's the path where most of the magnetic flux will travel for that magnet. The high and low E string magnets interact with the sides of the metal bridge sides, the other strings interact with the bottom of that metal bridge as those sides are too far away.

For our Tele why is this important? Those different path lengths mean that the metal bridge plate has differing magnetic fields at a given location in reference to each of the 6 string magnets N pole. That's the case as long as the string magnets aren't touching the bridge plate, typically there tape or other insulator installed under the magnets to facilitate this. As long as that tape is in place the magnets don't interact. Take the tape away and now the bridge plate is referenced to the S pole of the strongest magnet (i.e. this is likely the long G magnet on a staggered magnet bridge pickup). I've not tried it but removing that tape under a pickup with AlNiCo magnets (which are conductors) and having the magnets S poles actually touching the copper base plate of the pickup which is attached to the bridge plate with screws will (I expect) change the sound significantly likely for the worse.

6) Our strings are magnetized by magnetic fields that are pointing straight up, or straight down, or any compass point in between and in parallel with and perpendicular to the string (the magnetic field operates in spherical coordinates). I'm not aware of a magnetic field calculator that can really resolve these dynamics (for a low cost) so "cut and try" pickup design still prevails.

Just some quick thoughts to stimulate some discussion.

[Rodney Hamblen]

Guitar pickups typically consist of a ceramic oxide magnet or ALNICO 2,3,4 or 5. When you read about the ALNICOs the chemistry of the magnet is related to the tone. Yes and no. An ALNICO 5 can sound exactly like a ALNICO 2 but not using our typical technology.

I'm not aware of a widely used magnet charging mechanism that doesn't saturate the magnet material. In this situation the magnet material makes all the difference as different material blends allow different saturation levels of the finished magnet. Magnet charging is either done by coils and a DC source (older tech) or a highly charged large magnet in a press/clamping assembly. It doesn't have to be this way.

A magnet charging system that allows us to put a variable level of magnetism in our magnets would allow us to charge a ALNICO 5 to the level of a ALNICO 2. It would take some time to calibrate such a device but a DC powered/coil system using a variable DC voltage would do this.

Thankfully those of us who love G&L guitars have the option of installing magnets of our choice IF you're willing to disassemble your MFD pickup and remove the magnets. We're stuck on 1/8" diameter magnets but with a little effort you can spread the flux out using an improvised pole piece (think nail head). I believe that spreading the flux out will increase the bass based on opinions I've read but that's a subject for future work. Neodyium magnets are the usual material for these 1/8" rod magnets, in varying lengths.

Looking through replacement pickups today I've seen "52's" which use ALNICO 5 under the EAD and ALNICO 2 under the GBE strings. Stronger magnets under the bass strings and weaker magnets under the treble strings, the treble strings are the most susceptible to creating wolf tones. I also read about Brad Paisley's pickups by SD, using ALNICO 4 at the bridge and ALNICO 2 at the neck. ALNICO 4 are stronger than ALNICO 2 magnets, string vibration above the bridge pickup is greatly reduced to that of the neck and the strings are less susceptable to wolf tones with that pickup. Stronger magnets also provide more snap and percussive impact than weaker magnets. I assume the focusing part of the bridge pickup is the baseplate and classic Tele bridge design.

To summarize continuing the use of "saturation" magnetizers requires the industry to make different magnet chemical formulations to provide different magnetic strengths. For those of us willing to experiment MFD pickups can be modified with variable length 1/8" diameter magnets to achieve the same magnetic flux. And we can shape that flux using easily modified materials to spread that flux over wider diameters than 1/8".

When I bought my first G&L tribute in late 2019 I had no idea of the modification possibilities.