Do a new pickup need to activate or run in.?

[Joe Gwinn]

Why wouldn't that happen just from it sitting on a shelf?

I've never heard a change in a pickup, however, I have noticed my perception of that pickup has changed. Sometimes I'll wind up a new pickup, and I don't care for it. Then the next day I like it. I know the sound of the pickup has not changed however, because I recorded it the first time I played it, and now I also like the recording. I don't think the recording has changed!

So I think we just think the sound has changed, when in fact we have gotten used to it. It's like acquiring a taste in food.

Maybe it's just that you are better rested the next day.

Seriously, the wire can and does shift. While the tension per wire strand is in the tens of grams, 10,000 turns imposes 20,000 times the per-wire winding tension on the core (bobbin or magnets or slugs in flatwork), which can be (20)(20000)= 400 kilograms (880#), but isn't uniform. Over the next few days things will balance out to some kind of steady state.

A good parallel is the making of phase-stabilized coaxial cable. What do they mean by "phase-stabilized"? The manufacturer puts huge spools of freshly-made cable in a temperature-controlled warehouse, and spend 24 hours at 32 F, followed by 24 hours at 150 F, and so on for at least a week. This mostly anneals the various stresses and strains out, so the remaining changes are small and slow.

All my pickups are wax potted, so I know it has nothing to do with wire shifting, which I doubt happens anyway.

How can wax prevent wire shifting, given such large forces?

[Rick Turner]

This might be a good reason to try cryogenic treatment.

[big_teee]

This might be a good reason to try cryogenic treatment.

How does a country boy in the middle of the ouachita Mountains do this???
Later,
BigT

[copperheadroads]

I can do that here right now .just bring those magnets outdoors for a couple of minutes .......burrrrr

[Rick Turner]

You use Google to find a place that does cryogenic treatment and you go to the post office with a little box with one or more pickups in it and send them away. Or you get the brown truck with the gold letters on it to pickup the pickups and take them some place very, very cold... Or you use the US Pony Express if you're in such a remote place. Oh, they stopped running. OK, how about Railway Express? You have trains? Steam locomotives belching coal smoke?

[Mike Sulzer]

Maybe it's just that you are better rested the next day.

Seriously, the wire can and does shift. While the tension per wire strand is in the tens of grams, 10,000 turns imposes 20,000 times the per-wire winding tension on the core (bobbin or magnets or slugs in flatwork), which can be (20)(20000)= 400 kilograms (880#), but isn't uniform. Over the next few days things will balance out to some kind of steady state.

A good parallel is the making of phase-stabilized coaxial cable. What do they mean by "phase-stabilized"? The manufacturer puts huge spools of freshly-made cable in a temperature-controlled warehouse, and spend 24 hours at 32 F, followed by 24 hours at 150 F, and so on for at least a week. This mostly anneals the various stresses and strains out, so the remaining changes are small and slow.



How can wax prevent wire shifting, given such large forces?

Wind one turn on a pickup bobbin. Pull on one end with the other free, and it comes off. Wind on several turns and pull on one end. It does not come off, showing that frictional forces , wire to bobbin, and wire to wire, prevent the force from being transferred along the wire. You cannot transfer much force along the wire because it cannot propagate very far along the wire. This should be contrasted with an ideal frictionless multiple pulley system.

Anyway, I would not want the canonical 800 lb. gorilla standing on my pickup bobbins.

[Joe Gwinn]

Wind one turn on a pickup bobbin. Pull on one end with the other free, and it comes off. Wind on several turns and pull on one end. It does not come off, showing that frictional forces , wire to bobbin, and wire to wire, prevent the force from being transferred along the wire. You cannot transfer much force along the wire because it cannot propagate very far along the wire. This should be contrasted with an ideal frictionless multiple pulley system.

I'm not sure which way you are going here, but the wire is laid in turn by turn with the winding tension steadily applied (to the extent that the oblong shape allows). No sliding of wire past wire is needed to explain the buildup of core force. What sliding there is tends to relieve the force, but outer turns tend to prevent inner turns from slipping, so some kind of compromise is reached.

[Mike Sulzer]

I'm not sure which way you are going here, but the wire is laid in turn by turn with the winding tension steadily applied (to the extent that the oblong shape allows). No sliding of wire past wire is needed to explain the buildup of core force. What sliding there is tends to relieve the force, but outer turns tend to prevent inner turns from slipping, so some kind of compromise is reached.

With the oblong shape, the force, such as it is, is applied to the ends and tends to crush the pick up along its length. So in a Fender single coil, the force tends to collapse the two outermost magnets together by buckling the flat work. Do you really think that 800 lbs would not buckle it?

Consider anther example. A friend wraps several turns of rope around your forearm
firm, but not tight. If he now pulls on the two ends it tightens on your arm and you feel the squeezing. The turns of the rope slide relative to each other.

Now let us prevent the rope from sliding before the pulling by gluing the turns together with some super glue. Now when he pulls, there is no squeezing because the turns cannot slide with respect to each other.

In the pickup, sliding can take place only over a limited range of turns. The static friction forces balance the forces that would tend to crush the bobbin.

[David Schwab]

How can wax prevent wire shifting, given such large forces?

Because it's stuck together in a solid mass? I've cut wire off of my bobbins after it's been wax potted, and I can't easily separate any of the wire. It comes off as one solid piece.

[RedHouse]

Another thing is copper wire "settles" in time, sure it has a lot of tension while winding but in (short) time it' settles to it's new form an the stress goes away.
(dissipates)

When you wind a bobbin it has lot's of measurable tension (as Joe described above) but shortly thereafter the copper (being a highly maleable material) settles into it's place and become a stable mass. That huge winding force we tend speak of kind of "goes away".

Check it out by cutting a bobbin, off a winding.
(not cutting a winding off a bobbin)

The huge force present during winding the coil would collapse it (which it doesn't) when it is removed from it's form, and kind'a proves the tension of winding copper dissipates over (very little) time.
(I realised that re-winding lipstick style pickups)

You can wind a pickup coil with the tension your desire, then wait, and then remove it from the form and it has no tension. It is well formed and well set but all that tension does not collapse the coil when the bobbin is removed.
(I might not be saying it right)

[Chuck H]

When you wind a bobbin it has lot's of measurable tension (as Joe described above) but shortly thereafter the copper (being a highly maleable material) settles into it's place and become a stable mass. That huge winding force we tend speak of kind of "goes away"...
The huge force present during winding the coil would collapse it (which it doesn't) when it is removed from it's form, and kind'a proves the tension of winding copper dissipates over (very little) time...
You can wind a pickup coil with the tension your desire, then wait, and then remove it from the form and it has no tension. It is well formed and well set but all that tension does not collapse the coil when the bobbin is removed.

Something being skipped over is the fact that copper is not very elastic. That is, it doesn't contract as a result of kinetic energy when a force (like winding pressure) is removed. So the force applied to each wind is not cumulative and doesn't result in some enormous final pressure. The only way that could happen is if some amount of the force applied to the wire during the winding process were stored in the copper. But copper does't have the ability to store much physical energy.

[RedHouse]

Something being skipped over is the fact that copper is not very elastic. That is, it doesn't contract as a result of kinetic energy when a force (like winding pressure) is removed. So the force applied to each wind is not cumulative and doesn't result in some enormous final pressure. The only way that could happen is if some amount of the force applied to the wire during the winding process were stored in the copper. But copper does't have the ability to store much physical energy.

Yeah, that's like what I was trying to say.

Although there is some tension as can be observed when cutting windings off a bobbin, the windings peel-back a bit when you slice through so there is a bit of residual tension there, but not a huge bunch.

[David Schwab]

Yeah, that's like what I was trying to say.

Although there is some tension as can be observed when cutting windings off a bobbin, the windings peel-back a bit when you slice through so there is a bit of residual tension there, but not a huge bunch.

The tension appears near the ends, but often you can have lose windings in the middle of the coil. So it seems the wire doesn't slip and slide easily, since the coil is not being wound tight, like the rope on the arm in Mike's example. And even with rope on your arm, often the ends get tight, and not the rope in the middle, because of friction. I think all the winds support each other from slipping unless they are very lose, and also the tension is distributed amongst them. My coils are not all that tight when I wind them. They are kind of spongy. But after wax potting they are very solid.

[Joe Gwinn]

With the oblong shape, the force, such as it is, is applied to the ends and tends to crush the pick up along its length. So in a Fender single coil, the force tends to collapse the two outermost magnets together by buckling the flat work. Do you really think that 800 lbs would not buckle it?

It does buckle the flatwork. By a few thousandths of an inch. This (and the relaxation of the copper itself, as mentioned by other posters) is why the winding doesn't collapse into a little ball.

The key is that copper is far stiffer a material than forbon, so it takes very little crushing to reduce the force to whatever the forbon can sustain.

...

In the pickup, sliding can take place only over a limited range of turns. The static friction forces balance the forces that would tend to crush the bobbin.

One must distinguish single-layer from multi-layer coils. In multi-layer coils, later turns press upon earlier turns and increase the force required to start sliding. It's hard to predict how much sliding one will get in a practical coil, but note that the winding tension is maintained until the entire coil is wound, so there will be no sliding until after winding is complete.

[Joe Gwinn]

Because it's stuck together in a solid mass? I've cut wire off of my bobbins after it's been wax potted, and I can't easily separate any of the wire. It comes off as one solid piece.

Wax is soft, and a wire with those levels of force on it will simply swim through the wax, albeit slowly. Think cheese cutter, applied slowly.