Over/under restart

[Mike Sulzer]

Mike,

I was not talking about the temporary magnet that the string forms while over the permanent magnet. I was refereing to the string peak movement of its initial vibration soon after the initial pluck. To easily see the distance of the peak string movment try this simple experiment.

1. Use a 6" metal ruler next to the string being examined.

2. Pluck the string and observe the string movement from directly overhead.

3. Move the ruler vertically near the peak movement (near the neck pickup) and listen for the string just buzzing against the ruler.

4. Measure the distance from the string at rest to the hand held vertical ruler.

On my Strat using .010" to.046", the strings move about a plus and minus .05".

I'm sure this will vary depending on how hard the string is struck and on the thickness of the string gauge used with thinner strings having a wider peak string movement.

This would indicate that when the string rotates in the downward position it is closer to the magnet by about .05" and when in the upward position be .05" higher than the at rest position. To see the real effect of this simply listen or measure how the output of a pickup changes when the pickup height is changed .05" lower and when it is raised .05" higher than the starting pickup height position. Of course, this experiment all depends on striking the string at a conststant level.

Even when quickly attaching a guitar pickup to an oscilloscope, it is easy to see that one half of the peak output for the first few to first 10 or so cycles will be different from the other half by about 20% to 30%.

This is simply due to the strength of the magnetic field at the location where the string is cutting the magnetic flux being stronger near the magnet and weaker farther away.

While the string may retain some magnetization, the effect of what I speaking about above, has minimal consequences for this temporary string magnetization.

Run your FEMM model again using plus and minus .05" and let's see the result.

Thanks

Joseph Rogowski

Joseph,

Yes, 0.05 inches will make a huge difference! I had no idea it was so large. I will rerun FEMM tonight and I think it will show what you are saying.

But I am confused about the beginning of your post. We are talking about the string seeing different magnetic field strength close to and far away from the pole piece? That changes the amount of magnetization in the "string magnet", I think.

[Mike Sulzer]

What do I see?

David,

That drawing that you posted was too small to see. It was OK the second time.

Here is what I see:

What we need is a strong vertical field through the coil resulting from the vibration of the part of the string in question. Spreading of the field lines indicates a weakening of the field. The direction of the field is given by the direction of the lines. Looking at that drawing, I see that a strong vertical component will be induced in the coil only from vibration of the portion of the string very near the pole screw. The field weakens quickly as one moves away, and it becomes more horizontal. So I do not see anything unusual about this pickup.

[Mike Sulzer]

The total deviation fo the field now approaches 60%.
The effect is now quite large as you predicted, Joseph:
http://www.naic.edu/~sulzer/effectOfChangingField05.png.
You can see the asymmetry quite clearly.

[RedHouse]

So why did you start a new thread just to continue dialog from the other thread?

Mod's, can we roll this back into the last thead where it belongs so we don't have to have two threads on the same dialog?

[Mike Sulzer]

So why did you start a new thread just to continue dialog from the other thread?

Mod's, can we roll this back into the last thead where it belongs so we don't have to have two threads on the same dialog?

I cannot post on the old one any more. Can you?

[David Schwab]

So why did you start a new thread just to continue dialog from the other thread?

Mod's, can we roll this back into the last thead where it belongs so we don't have to have two threads on the same dialog?

I didn't close that thread. I have to assume it was tboy as there aren't any other mods in the pickup makers section (Dr. S is no longer an active mod).

So I assume the arguing got out of hand.

[RedHouse]

I didn't close that thread. I have to assume it was tboy as there aren't any other mods in the pickup makers section (Dr. S is no longer an active mod).

So I assume the arguing got out of hand.

Maybe this one will get closed too.

[Rick Turner]

Well, I'm going to stay the hell out of this discussion because I don't particularly like arguing with those who duck questions and jam simplistic theories down the throats of real hands-on pickup makers and inventors...of whom there are a number here. I had been involved with this forum to share several decades worth of information and to learn things, not be dismissed by those who think that their interpretations of book theory trump experience and actual listening. In the pickup world we seem to range from absolute smoke and mirrors mythology to deaf and blind pseudoscience. I'm more interested in what is in the middle which I believe to be a deeper space, and I've learned that science is always one or more steps behind reality in explaining what we can perceive. And then there is the simple fact that some folks just can't perceive...they really can't hear the subtle effects that are going on. I find this incredibly true in the acoustic guitar world as well. Weird... There are a bunch of people who just can't help listening with their eyes, not ears...

[RedHouse]

... I had been involved with this forum to share several decades worth of information and to learn things...

And this forum is all the better for it, most of us appreciate your posts.

Don't let Mike get under your skin, it's his modus operandi, it's just what he does ...ad nausium ...ad infinitum.

[Dave Kerr]

It just seems counterintuitive to me that the magnetic field emanating from the small section of string that's temporarily magnetized, magnetized to varying strength dependent upon distance from the pole piece, is the sole source of magnetic field change inside the coil that induces a voltage. Wouldn't vibrating magnet A, in close proximity to stationary magnet B, cause at least a subtle change in the flux of magnet B? What seems more intuitive is to consider the string as a part of the magnetic circuit of the pickup, but with a substantial air gap.

[Mike Sulzer]

It just seems counterintuitive to me that the magnetic field emanating from the small section of string that's temporarily magnetized, magnetized to varying strength dependent upon distance from the pole piece, is the sole source of magnetic field change inside the coil that induces a voltage. Wouldn't vibrating magnet A, in close proximity to stationary magnet B, cause at least a subtle change in the flux of magnet B?

Yes, and this effect is allowed for by recognizing that the material of the core can permeable. For example, alnico magnets are somewhat permeable, and the steel cores are more so. The permeability increases the the effect of the vibrating temporary magnet. But it is not necessary to have a permeable core. David builds bass pickups using neos as the core. Neo is essentially no more permeable than free space. He loses a bit of output, but not as much as you might think. The effect of even a highly permeable material is limited when the magnetic circuit contains large gaps. This is why things like motors, generators, and transformers use tightly coupled, low leakage magnetic circuits.

What seems more intuitive is to consider the string as a part of the magnetic circuit of the pickup, but with a substantial air gap.

That has to work, of course, but it cannot predict anything different from the law of induction since the rules of magnetic circuits are derived from it. I find that it is much more convenient to use the law of induction directly since it is the best statement of the physics.

[David Schwab]

David builds bass pickups using neos as the core. Neo is essentially no more permeable than free space. He loses a bit of output, but not as much as you might think.

Actually I use steel cores, but I do use ceramic magnets as cores in others.

Q-Tuners have neo magnets at the core of the coils, along with air.

[Mike Sulzer]

Actually I use steel cores, but I do use ceramic magnets as cores in others.

Q-Tuners have neo magnets at the core of the coils, along with air.

Sorry about that. I thought you showed a design here that used neo bars only in the core.

[Dave Kerr]

I'd made a pickup for a cheapo archtop that my kid took to summer camp. I used laminate samples from Home Depot for flatwork and wound 42 AWG wire on a taped neo magnet core, it sounds great and is thin enough to just tuck under the strings at the end of the fingerboard. I don't think I took/posted any photos of it (it was not an aethetic triumph, just a utilitarian one), but I may have mentioned it here.

[RedHouse]

I'd made a pickup for a cheapo archtop that my kid took to summer camp. I used laminate samples from Home Depot for flatwork and wound 42 AWG wire on a taped neo magnet core, it sounds great and is thin enough to just tuck under the strings at the end of the fingerboard. I don't think I took/posted any photos of it (it was not an aethetic triumph, just a utilitarian one), but I may have mentioned it here.

I'd love to see that!