technical Question about Eddy Currents

[WDeeGee]

Does anyone have a good physics understanding of how Eddy currents work?

They mute some of the high end and obscure note definition somewhat. The problem is this: I have a nice, dark sounding humbucker but with a humbucker cover it sounds just too dark. Without, it sounds great, but the bobbins are white and it doesn't look good in the guitar. It had me thinking... do Eddy currents pass through the HB cover from solder to solder?

Is it possible to prevent Eddy currents if you only solder the cover on one side (or use a glue gun instead); and isolate the inside of the cover with a varnish so it can't touch the baseplate anywhere electrically?

[freefrog]

Re: technical Question about Eddy Currents

No, the absence of solder won't prevent Foucault currents. And no, insulating the cover from the baseplate won't cancel them either (I'm sure of this statement since I've tested what you say a while back, with plastic tape instead of varnish).

Regarding the technical side and possible solutions, the work published by this guy deserves to be quoted (and will save my precious time. LOL):

http://kenwillmott.com/blog/wp-content/uploads/2016/11/Pickup_Cover_Geometry.pdf

FWIW. :-)

[WDeeGee]

Re: technical Question about Eddy Currents

Thanks! That's a very interesting paper!

[uOpt]

Re: technical Question about Eddy Currents

Does anyone have a good physics understanding of how Eddy currents work?

They mute some of the high end and obscure note definition somewhat. The problem is this: I have a nice, dark sounding humbucker but with a humbucker cover it sounds just too dark. Without, it sounds great, but the bobbins are white and it doesn't look good in the guitar. It had me thinking... do Eddy currents pass through the HB cover from solder to solder?

Is it possible to prevent Eddy currents if you only solder the cover on one side (or use a glue gun instead); and isolate the inside of the cover with a varnish so it can't touch the baseplate anywhere electrically?

No, they literally go in circles just within the cover material. Even if you didn't ground them at all you would get the same dampening.

Having said that, the effect is similar to a lower ohm volume pot, so if you have 250 kOhm now you can try whether 500 makes the sound acceptable with cover on.

[frankfalbo]

Re: technical Question about Eddy Currents

The trouble with comparing them to any other phenomenon like pot values (which impact the resonant peak, whereas eddy currents generate their own independent response curve) is that they are also velocity sensitive in my experience. There are some lab tests that can show you the response curve and how to mimic it with capacitance for example, but the net player experience is not the same for someone with a dynamic picking hand. There’s a feel difference.

[freefrog]

Re: technical Question about Eddy Currents

The trouble with comparing them to any other phenomenon like pot values (which impact the resonant peak, whereas eddy currents generate their own independent response curve) is that they are also velocity sensitive in my experience. There are some lab tests that can show you the response curve and how to mimic it with capacitance for example, but the net player experience is not the same for someone with a dynamic picking hand. There’s a feel difference.

+1!

Glad to read you, Frank. I hope all is fine for you and your family in these strange times of "C19" - which sadly, is not a capacitor...

[d2718]

Re: technical Question about Eddy Currents

I don't have anything to add to this thread; I just wanted to say thanks for linking to that paper. That's probably something that should be in The Vault.

[ehdwuld]

Re: technical Question about Eddy Currents

have you tried plastic covers?