Basic Magnet Questions

[Amit]

Bill Lawrences SCN does not use neos.. it uses SmCo magnets, hence the name, Samarium Cobalt Noiseless.

The magnets are actually attached to a keeper, which he calls a moderator bar.

If you are going to use alnico rods, you don't need the neos. A lot of the early stacks were made that way.

For the sake of the concept I said "Neo" as a short for "any strong rare earth magnet"

With just magnet rods a la Dimarzio/Kinman/etc your top coil gets more differential string signal and the bottom coil gets more common mode noise. it's never a cut and dry separation like an external dummy coil.
In BL's patent the stacked coils work exactly like a PAF, both coils see common mode noise and string signal.

[automan]

I ordered my neo and SmCo magnets today. I am greatly looking forward to prototyping with them.

[David Schwab]

With just magnet rods a la Dimarzio/Kinman/etc your top coil gets more differential string signal and the bottom coil gets more common mode noise. it's never a cut and dry separation like an external dummy coil.

It's also amazing what the bottom coil sounds like on its own. Not much high end at all.

In BL's patent the stacked coils work exactly like a PAF, both coils see common mode noise and string signal.

The newer designs, like Kinman, make the bottom coil more sensitive to hum, and they don't run the magnets through. DiMarzio followed suit (read: ripped off) the Kinman design, and then Beller did an update for the new Duncan stacks.

Here's the patents:

DiMarzio: 5811710, 5908998

Beller: 7166793

I've had experience with the DM version, the Virtual Vintage Solo Pro, and it's actually a really nice sounding pickup. The bottom coil is wound a lot less, and with larger wire, and it has extra steel slugs to raise its inductance. The top coil has the shield around it.

I've made a few stacks, both the old way and the Lawrence way. In both cases they are very bright and a bit thin sounding. I wasn't totally happy with them. You are forgetting that a PAF has two opposite magnetic poles facing the strings. This puts the two out-of-phase coils back in again.

With a stack you end up with reduced low end because the coils are out-of-phase, and don't have the benefit of picking up the strings with two polarities. If you reverse the polarity of the bottom coil, they get very loud and dark sounding, just like a single coil would to 24K would. But then they also hum.

PAFs add the signal from the two coils together in the lows and mids, and cancel out a small amount of top end. Stacks cancel out some low end. It's the opposite situation.