Baseplate for Tele bridge pickup, Strats, P-90 and Humbucker

[pablogilberto]

Hello!

some questions


#1 
Based on my understanding, Tele Bridge pickup and some Strats uses a copper plated steel as a baseplate.

Can you share your thoughts on what is the effect of this?


#2
Since it is a steel (magnetic), I thought that it would increase the magnetic strength.
But upon checking with a magnet meter, it actually weakens the magnet strength.

So why do we use it on a Tele bridge pickup?


#3
The P-90 and humbucker baseplate meanwhile uses Nickel Silver or Brass
Both are non-magnetic

Based on my measurement, they actually increase the magnet strength.


Why not use Nickel Silver or Brass for Tele bridges?

[gckelloch]

I've read conflicting results for Steel, but never that Brass or Ni increases Gauss. My understanding from a Dr. Scott Lawing blog on the Zexcoil site is that a Steel baseplate can increase efficiency by drawing more flux lines through coils. I'm not sure how close together the flux lines are in magnetic alloys, but it can vary. Is it possible that the Gauss probe tip is either between or right on a flux line in your measurements? Maybe moving it around on the pole top will give different results, and you could use the highest value for each example.

[pablogilberto]

Using a copper-plated steel Tele bridge pickup baseplate, I really get weaker magnetic strength readings at the top of the polepieces.

I tried experimenting with a P-90 with and without a Nickel Silver baseplate and was able to confirm that the Nickel Silver plate does increase the magnet strength a little.

[gckelloch]

And moving the Gauss probe around on the pole tops makes no difference?

I'd expect the Gauss to decrease at the pole tops when Steel is attached to the bottom, but not to increase when NiSi is attached to the bottom. Is that when replacing a Steel baseplate in the P90 with NiSi? Perhaps it's the same reasoning as with the Tele pickup. The Steel baseplate draws some flux power away from the Steel screw tops, but NiSi does not. Does the p90 sound louder, softer, thinner, or fatter with the NiSi vs Steel baseplate?

[pablogilberto]

Moving the Gauss probe around surely makes a difference in the reading, I'm taking note of the min and max reading.
Using a Nickel Silver increases it slightly.
Using a Steel baseplate, lowers it significantly.

Using a steel baseplate in a P-90 style pickup makes it sound softer / weaker / lower output

[gckelloch]

Surprising. Comparisons on YT of Strat pickup Steel baseplates have a net effect of stronger bass. Maybe the same effect doesn't happen if the pickup poles are Steel?

[pablogilberto]

I tested steel baseplates in strats pickups (with Alnico polepiece) and they also tend to weaken the magnet strength at the top.

I think the perceived stronger base is due to the increased inductance when a baseplate is added.
Resonant freq will be lower (stronger bass).

[gckelloch]

Someone on the Music Electronics Forum measured the difference and found a Steel baseplate only marginally increases inductance. I don't see how lowering the resonance from something like 4kHz to 3.7kHz would increase bass. Perhaps the slightly reduced high-end and string pull might be part of the effect, but I also don't see why it's so hard to believe that a highly permeable alloy under the coil would draw more of the flux lines from the strings through the coil if the poles aren't very permeable. Did you read Dr. Lawing's blog about the WRHB pickup?

Another reference for the effects of high permeability material in pickups is the measurements ms took of his unique ferrite core hum-canceling pickups:

guitarnuts2.proboards.com/post/103506/thread

It shows the two pickups have nearly the same inductance, and the same Gauss/Tesla beyond 0.1" from the surface, yet the output of the ferrite core pickup is ~10dB higher. I may misunderstand something about magnetism, but what else would account for the output increase other than flux lines from the strings somehow functioning more efficiently in the coil? I assume it's mainly from more lines and/or the same amount of lines being drawn more through the coil into the ferrite cross piece. I suppose those string flux lines also cause flux to emanate back from the core and cross piece, which in turn contributes something to the output. Could be "all of the above".