Magnet type and noise

[CarlosG]

Hi!
Recently i noticed that the a2 magnet makes more noise than the a5, it's like a hum.
So will the ceramic magnet be the quietest (I mean noise)?

 

[Chistopher]

Magnet doesn't affect noise. Remove the magnet entirely and it will be just as noisy as a neodynium.

 

[Rex_Rocker]

I think the stronger magnet would be the noisiest under the same amp/gain settings, but that's because the whole pickup is louder and the signal to noise ratio is always constant.

I'm thinking if you find the pickup is humming when you swapped the magnet, something might be in the wrong place when you put it back together?

 

[Chistopher]

It would be the opposite.

A pickup's magnet does not pickup noise. Louder magnet would mean louder guitar signal but the noise level would stay the same. Therefore it would have a better signal to noise ratio.

 

[Chistopher]

If a guitar's magnet picked up noise, RWRP would be pointless.

 

[freefrog]

With lab gear, it's possible to notice a wee bit more noise when the ferrous content of the magnetic circuit and therefore the inductance are increased by a new magnet, as it's normally the case with an A2 after an A5. Maybe it can be heard under very high gain and/or at really high volume. Now, in such a situation and as suggested by Rex_Rocker, I'd start by checking the wiring - including the ground connection of the pickup itself.

 

[Rex_Rocker]

If a guitar's magnet picked up noise, RWRP would be pointless.

My bad. I don't mean a magnet picks up hum.

 

[CarlosG]

With lab gear, it's possible to notice a wee bit more noise when the ferrous content of the magnetic circuit and therefore the inductance are increased by a new magnet, as it's normally the case with an A2 after an A5. Maybe it can be heard under very high gain and/or at really high volume. Now, in such a situation and as suggested by Rex_Rocker, I'd start by checking the wiring - including the ground connection of the pickup itself.

I play with high gain. It's not the first time I've noticed that after changing the magnet to a2 it hums more than a5

 

[Mincer]

Honestly, I've never noticed this at all.

 

[freefrog]

I play with high gain. It's not the first time I've noticed that after changing the magnet to a2 it hums more than a5

So, see my explanation...

Increasing the ferrous content of magnetic circuits is a well known way to make coils noisier... A relatively famous boutique winder even managed to make a noise cancelling coil of a few hundreds Ohm as (anti)noisy as a 6k single coil by winding it around a metallic bobbin (laminated to avoid eddy currents in this case)... Most of this noise is obviously cancelled in humbucker mode. But coils being not totally symetrical in Gibson style humbuckers, some residual noise can be measured.

Anyway and to keep thinking out loud : typically, swapping an AlNiCo magnet for a ceramic bar will/would/should increase the magnetic flux and decrease the inductance, explaining the kind of tonal differences noticed in such cases...
Obtaining the same inductance from both solutions would require to dewind coils for the AlNiCo bar but the loss of output level due to its weaker magnetism would worsen...
Encapsulating the AlNiCo bar in electrically insulating tape would make it non-conductive like a Ceramic bar but without lowering the inductance...
"Airing" the pickup in the DiMarzio fashion would weaken the magnetic field due to Ceramic but without increasing the inductance - unless some ferrous slugs would be added in bobbins, giving the same amount of iron than with an AlNiCo bar.
Or how my thoughts chase their tail. <:0)

If I had your guitar here, I'd lab test it through various changes, including the use of a fiber baseplate or a layer of insulating tape between magnet and baseplate, just to see what happens with residual noise.

Do what you want and be happy.

 

[freefrog]

Well, Carlos, having a bit of free time, I've double checked my statements above and to answer to your original question: no, a ceramic mag doesn't frankly make a humbucker quieter than an A5. At least not if it's a typical ceramic bar with strong magnetism.

Below is a zoom on the noise floor at low frequencies (20hz-100hz), for a SAME P.A.F. style humbucker loaded with different magnets : A2 (average strenght: 480G, it's a rather strongly charged Gibson magnet), A5 (560G), ceramic (1350G). The inductance of the pickup is displayed in each case. Each vertical step measures 1dB.
The 4th line showing the lowest noise comes from the pickup with the A2 separated from the baseplate by a strip of adhesive tape.
What my zoomed pic doesn't show is how the pickup with this insulated A2 is noisier at high frequencies, albeit less noisy in the "hum" range...
A low gaussed ceramic mag should make the pickup less noisy than in this test but I haven't one at disposal right now.




Incidentally, the 2d pic below zooms on the resonant peaks obtained with these 4 solutions. The lowest pitched peak comes from the A2, as expected. The insulated A2 causes a slightly higher peak because of the lower eddy currents due to the insulating material. The A5 makes the resonant peak higher pitched but less than with the ceramic bar. Nothing surprising here: reflects the inductance measurements mentioned in the pic.



FWIW. HTH.