EMG active pickups preamp circiut schematic.

[Mike Sulzer]

As a rule of thumb,

I like your rules of thumb. Just like to point out that getting say 20db reliably time after time and under all condition requires aiming for somewhat better.

Perfectly matched coils are still susceptible to electrostatic pickup if not shielded.

Thank you for writing that: one of my pet peeves. In fact, writing that and arguing that it is correct contributed to me getting kicked off another forum. It is interesting that most humbucker users do not use a cover. But the base plate, even though it covers just the bottom, does have a significant shielding effect. So it could be worse.

[David Schwab]

Thank you for writing that: one of my pet peeves. In fact, writing that and arguing that it is correct contributed to me getting kicked off another forum.

Yeah, but Mike, you would also argue about things, like when you said to me that stacking a bunch of magnets doesn't increase the strength, when clearly it does.

And Deb has a hair trigger for kicking people off lately...

It is interesting that most humbucker users do not use a cover. But the base plate, even though it covers just the bottom, does have a significant shielding effect. So it could be worse.

Because they don't sound the same with metal covers, which is why people started taking the covers off. You can get better noise reduction without changing the tone by using shielded plastic covers.

Traditional humbucker parts are really quite archaic. Covers are popular these days because of the way they look.

[Joe Gwinn]

I like your rules of thumb. Just like to point out that getting say 20db reliably time after time and under all condition requires aiming for somewhat better.

The rule of thumb was about the acoustic consquence of various levels of hum cancellation. This is inherently sloppy, as people are involved.

Achieving these levels of cancellation is another matter entirely. Although matching turns counts to within 10% doesn't seem that hard to me.

Thank you for writing that: one of my pet peeves. In fact, writing that and arguing that it is correct contributed to me getting kicked off another forum.

Was it something you said?

What was their counterargument?

It is interesting that most humbucker users do not use a cover. But the base plate, even though it covers just the bottom, does have a significant shielding effect. So it could be worse.

It's a tradeoff to be sure. Most covers do muffle the sound.

[Mike Sulzer]

Yeah, but Mike, you would also argue about things, like when you said to me that stacking a bunch of magnets doesn't increase the strength, when clearly it does.

And Deb has a hair trigger for kicking people off lately...

David, I think we both know that stacking disc magnets, that is, flat things magnetized along the short dimension, increases the strength, and as your reference says, makes a magnet of the same strength as a single magnet of that geometry.

But making very long rod magnets out of shorter rod magnets has little effect. (magnetized along the long dimension) Do you remember what we were discussing?

It took Deb several years to kick me off, but yeah, the final event really was hair trigger, and kind of surprised me.

[David Schwab]

Do you remember what we were discussing?

Yeah, I had about 10 neo bar magnets stuck together, and was able to pick up a chromed nickel silver Gibson EB-0 pickup cover. One or two of the same magnets wouldn't do it, and a big stack of ceramics wouldn't do it either.

I think the discussion was about the effect of chrome plating on the tone of a pickup.

This photo should refresh your memory.

[Mike Sulzer]

Was it something you said?

What was their counterargument?

No counter argument necessary. On MIMF staff members are experts, and what they say is correct, period.

Charlie Falco claimed that:
1. The magnetic material in a pickup core does not affect the sensitivity to fields. Thus, a coil with with an air core can be used to cancel perfectly with one with a core of magnetic material.
2. Counter wound coils also cancel electric fields, not just magnetic fields.

He wrote that he learned all of this years ago by experimentation, and that any experiment that I did was simply wrong; he ignored any theoretical argument. The latter is understandable, of course. He knows nothing about the physics.

I suspect that there were some people reading this stuff who knew better, But I sure did not get much support.

[David Schwab]

I suspect that there were some people reading this stuff who knew better, But I sure did not get much support.

I didn't agree with you about the air coil thing, but have since changed my stand on that. It does work though, since that's how Alembic does it. They have a plastic core in the hum canceling coil.

But having metal cores makes it more efficient. But if you look at a standard Gibson humbucker, the cores are hardly the same.

The DiMarzio stacked single coils have extra metal in the bottom coil (with no magnets), but also fewer windings than the top coil with the magnets. It works very well.

So they don't have to match, coil or core wise to cancel hum, and I think that was your argument.

[Mike Sulzer]

I didn't agree with you about the air coil thing, but have since changed my stand on that. It does work though, since that's how Alembic does it. They have a plastic core in the hum canceling coil.

But having metal cores makes it more efficient. But if you look at a standard Gibson humbucker, the cores are hardly the same.

The DiMarzio stacked single coils have extra metal in the bottom coil (with no magnets), but also fewer windings than the top coil with the magnets. It works very well.

So they don't have to match, coil or core wise to cancel hum, and I think that was your argument.

When the two coils are the same, as they were in Charlie's measurement you do need the magnetic core to get the same sensitivity to magnetic fields. The measurement I made at the time gave a 14 db increase in hum when the screws in a PAF type were removed. Proof enough I would have thought, especially since someone had earlier described a similar measurement. Didn't I write recently that the longer length of the screws (and I should mention the large head as well) counteracts the smaller diameter compared to the slugs? I think the sensitivity of the two coils is thus about the same.

Of course you can use an air core for a dummy if it is some combination of larger/greater number of turns.

By the way, in that other discussion you mentioned, were you not concerned with why the ceramics would not do it no matter how many you used in the stack? That would be for the reason I mentioned above.

[David Schwab]

When the two coils are the same, as they were in Charlie's measurement you do need the magnetic core to get the same sensitivity to magnetic fields. The measurement I made at the time gave a 14 db increase in hum when the screws in a PAF type were removed. Proof enough I would have thought, especially since someone had earlier described a similar measurement. Didn't I write recently that the longer length of the screws (and I should mention the large head as well) counteracts the smaller diameter compared to the slugs? I think the sensitivity of the two coils is thus about the same.

Of course you can use an air core for a dummy if it is some combination of larger/greater number of turns.

Right, but as I have said in the past, in the real world it's not always that way. Alembic wind both coils exactly the same, and they are wired in series, so they aren't mixing the two to get them to cancel. The top coil has a magnet, and the dummy has nothing except a plastic spacer the same size as the magnet of the top coils.

And you talked about removing the screws from a humbucker coils and it changing the rejection of noise, but the two cores were never equal to start with!

Then there's the Suhr Guitars system that uses a low resistance larger area coil. Dummy coils seem to be going in that direction as to not effect the string sensing coil's tone. They don't get 100% rejection, but they don't really need to.

By the way, in that other discussion you mentioned, were you not concerned with why the ceramics would not do it no matter how many you used in the stack? That would be for the reason I mentioned above.

The ceramics also get stronger stacked up, it's real obvious when you start stacking them and try to lift objects. But my point was that the neos are so strong that they were able to lift the cover. One of those neos is as strong as that whole stack of ceramics. I've recharged ceramics with two of the neos.

I can pull the ceramic apart, but it's hard to pull the neos off the stack. I just got a stack of 30 neos, and it was a real chore to get one off!

[Joe Gwinn]

No counter argument necessary. On MIMF staff members are experts, and what they say is correct, period.

Charlie Falco claimed that:
1. The magnetic material in a pickup core does not affect the sensitivity to fields.

Nonsense.

Thus, a coil with with an air core can be used to cancel perfectly with one with a core of magnetic material.

This can work, if the area-turns-permeability products of the two coils match reasonably well.

Counter wound coils also cancel electric fields, not just magnetic fields.

Nonsense.

He wrote that he learned all of this years ago by experimentation, and that any experiment that I did was simply wrong; he ignored any theoretical argument. The latter is understandable, of course. He knows nothing about the physics.

Nor were his experiments well enough designed.

I suspect that there were some people reading this stuff who knew better, But I sure did not get much support.

Given that it got you bounced, one can understand their reluctance.

[salvarsan]

... one can understand their reluctance.

(Aaaaaargh.)

Must ... not ... make ... vile ... pun.

-drh

[Mike Sulzer]

Right, but as I have said in the past, in the real world it's not always that way. Alembic wind both coils exactly the same, and they are wired in series, so they aren't mixing the two to get them to cancel. The top coil has a magnet, and the dummy has nothing except a plastic spacer the same size as the magnet of the top coils.

I do not know what kind of magnet they use, but if a magnet alone is used as the core and it has low permeability, such as neo, then an air core dummy would be the proper thing to use. Using a neo magnet alone is like using an aircore.

And you talked about removing the screws from a humbucker coils and it changing the rejection of noise, but the two cores were never equal to start with!

And your evidence for that is???? Of course two cores that are physically different can have the same sensitivity if they are designed to. Give the engineer who designed the Gibson humbucker some credit. Some people actually do understand what they are doing.

Then there's the Suhr Guitars system that uses a low resistance larger area coil. Dummy coils seem to be going in that direction as to not effect the string sensing coil's tone. They don't get 100% rejection, but they don't really need to.

No reason why they cannot get good rejection with that system, at least over a fairly wide range of harmonics.

The ceramics also get stronger stacked up, it's real obvious when you start stacking them and try to lift objects. But my point was that the neos are so strong that they were able to lift the cover. One of those neos is as strong as that whole stack of ceramics. I've recharged ceramics with two of the neos.

Of course the stack gets stronger, up to a point.

[David Schwab]

I do not know what kind of magnet they use, but if a magnet alone is used as the core and it has low permeability, such as neo, then an air core dummy would be the proper thing to use. Using a neo magnet alone is like using an aircore.

Ceramic. They have no metal parts in the pickup.

And your evidence for that is???? Of course two cores that are physically different can have the same sensitivity if they are designed to. Give the engineer who designed the Gibson humbucker some credit. Some people actually do understand what they are doing.

Seth Lover didn't want the adjustable screws, and he didn't design the pickup that way. The prototype used for the patent had two sets of non adjustable slugs. He said Gibson wanted adjustable poles to make the pickup more marketable, since the P-90 had them, and Fender didn't.

The screw coil is weak, you can hear it for yourself.

No reason why they cannot get good rejection with that system, at least over a fairly wide range of harmonics.

The samples I have heard sound very good. If you've ever worked with dummy coils you find out they can ruin the tone of the string sensing coil. The Kinman/DiMarzio method works really well too.

Of course the stack gets stronger, up to a point.

Of course... it couldn't be stronger than a single magnet of the same size and type, but it is as strong.

[Mike Sulzer]

Ceramic. They have no metal parts in the pickup.

What is the permeability of the ceramic that they use?

The screw coil is weak, you can hear it for yourself.

If the screw coil sounds weak, then it must be at least several db down. If this is a reflection of how well the pickup cancels hum, then it cannot do it very well. Actually, it is more complicated than that. Changing the height of the screws changes the signal strength (from the string) a lot because the string is close. But it does not change the sensitivity to hum as much if you do not move too far because the hum source is far away and the screws are longer than the height of the coil.

So what does your observation that the screw coil is weak mean? It certainly does not demonstrate that the screw coil has a weaker sensitivity to hum.

The samples I have heard sound very good. If you've ever worked with dummy coils you find out they can ruin the tone of the string sensing coil. The Kinman/DiMarzio method works really well too.

Of course. The idea is to make a low inductance coil with the same sensitivity to hum and put it in series rather than double the inductance and kill the highs with a coil like the pickup coil. Am I missing your point?

Of course... it couldn't be stronger than a single magnet of the same size and type, but it is as strong.

That is not the issue. What happens as you make the stack deeper? Does each additional magnet added to the back of the stack increase the strength at the other end as much as the previous magnet did. If there is a decrease, what factors affect it?

[David Schwab]

What is the permeability of the ceramic that they use?

I have no idea. But, yes a ceramic magnet is closer to an air core than an alnico.

So what does your observation that the screw coil is weak mean?

That maybe there is less metal in the screw coil? It might also be less efficient because the screws extend out the back.

It certainly does not demonstrate that the screw coil has a weaker sensitivity to hum.

If the coils are the same, but the inductance is different, they should throw that off, no? That's what you were pointing out about removing the screw poles.

I agree that everything should be matched ideally. And that's what I would want to do with a new pickup design, but my point has always been that it hasn't been done that way so far, and still works well enough. But there's always room for improvement.

Of course. The idea is to make a low inductance coil with the same sensitivity to hum and put it in series rather than double the inductance and kill the highs with a coil like the pickup coil. Am I missing your point?

My point was that the dummy coil in these systems has an air core, while the pickup does not. This is similar to the situation described by you when you removed the screws from the coil. Obviously with the Suhr system, the larger area of the coil makes up for the lack of a core.