Interested in the Dan Armstrong Plexiglass Bass-style pickup design...

[Chris Turner]

Well, here it is in the test bass:






I tried getting some audio clips together, but something's wrong with my setup. Oh well. It definitely sounds a lot like I thought it would... like two pickups in one. The top coil is nice and bright/zingy (42 AWG wire, wound to just under 5K), and the bottom coil gets into mudbucker territory (43 AWG wire, wound to about 23K!). With both coils turned up, the nice zingy tone of the top coil remains, but the bottom coil adds a good solid bottom end to it. Not much frequency cancellation here, as they both sense about the same length of string. Pretty cool.

I've got each coil hooked up to its own volume pot. Surprisingly, I can't detect any difference in output, whether I've got only the top coil volume all the way up, both volumes all the way up, or just the bottom coil volume all the way up. I wonder if this might change if I just used a single blend pot for both coils...?

[StarryNight]

Are those magnets charged on the faces or the edges?

[Chris Turner]

Are those magnets charged on the faces or the edges?

The magnets are charged on the faces. The same polarity faces inward for each one.

[David King]

Chris, without the steel base-plate how do the neos couple with the pole pieces? Maybe I'm missing something in the last photo.
In fact I'm a little confused by the original design as the upper magnet wouldn't couple very well either.
I'm pretty sure the original's magnets must have been edge magnetized and not charged through the face like yours or there would have been very little coupling there.

Having such a wide air-gap between the neos and the poles as you seem to have must tame the brightness/ brittleness of the neos considerably if my theory is correct. Have you tried just slapping a neo or two onto the bottom of the slugs?

[Chris Turner]

Chris, without the steel base-plate how do the neos couple with the pole pieces? Maybe I'm missing something in the last photo.
In fact I'm a little confused by the original design as the upper magnet wouldn't couple very well either.
I'm pretty sure the original's magnets must have been edge magnetized and not charged through the face like yours or there would have been very little coupling there.

Having such a wide air-gap between the neos and the poles as you seem to have must tame the brightness/ brittleness of the neos considerably if my theory is correct. Have you tried just slapping a neo or two onto the bottom of the slugs?

In the case of my pickup, the neos don't directly touch the poles at all. Even so, I can tell that the poles are magnetized quite well. I haven't yet tried slapping a neo on the bottom... I was just trying to recreate the original pickup's design (or so I thought :-) ) to see what it would sound like. I'll try that, though. But honestly, that top pickup is plenty zingy as it is. The bottom one is very fat, as I expected from a 23K coil, but the neos being so far away obviously plays a role too.

[Chris Turner]

Chris, without the steel base-plate how do the neos couple with the pole pieces? Maybe I'm missing something in the last photo.
In fact I'm a little confused by the original design as the upper magnet wouldn't couple very well either.
I'm pretty sure the original's magnets must have been edge magnetized and not charged through the face like yours or there would have been very little coupling there.

Having such a wide air-gap between the neos and the poles as you seem to have must tame the brightness/ brittleness of the neos considerably if my theory is correct. Have you tried just slapping a neo or two onto the bottom of the slugs?

I've been looking back into this design...

David King, you mentioned trying to slap a neo magnet on the bottom of the poles. Do you have any insight as to why Bill Lawrence (who I assume did the bulk of the design of the pickup I was trying to "copy") would have placed the magnets outside of the coils? Wouldn't the same effect have been had by doing what you suggested and putting magnets on the bottom of the poles?

Also, what's really the difference between a stacked humbucker, and a dual-tone single coil? Just the fact that the two coils don't cancel hum because of the way they're wound?

[Mike Sulzer]

Let me see if I can summarize how the original and Chris's work:

The original: It is two coils deep so you do not want to make it too much deeper with a thick magnet on the bottom. So instead use a thinner steel plate on the bottom to carry field in. You put a magnet, edge magnetization, like a humbucker magnet, out on one edge with the field lines facing down (for example) and the lines continue inward and up the pole blade. You put another one on the other edge also field lines down, and they go up the pole as well, giving a stronger field. Who knows what the upper magnet is intended for, but it will add some magnetization. Then you have two coils, one over the other. The bottom one has a lot more turns, so it has a lower resonant frequency, and it would have a higher output, too, but since it is farther from the strings the volume effect is not so big, or maybe not at all. Electronics blends the outputs of the two coils, and you get one, the other, or some combination. The difference resonant frequencies give distinctly different sounds. Also, the lower coil might have some additional eddy current losses in the steel plate, damping the resonance a bit and raising it some.

Chris's: It uses strong neodymium magnets, face magnetized. The fields point in; the fields come in to the poles, turning up and going around. The horizontal components cancel, and you are left with field going up the poles. The upper magnet adds some additional field strength in a similar way. The coils work the same way as the original, but no bottom steel plate for eddy current losses.

If you have enough magnetization the way its, why change it?

I've been looking back into this design...

David King, you mentioned trying to slap a neo magnet on the bottom of the poles. Do you have any insight as to why Bill Lawrence (who I assume did the bulk of the design of the pickup I was trying to "copy") would have placed the magnets outside of the coils? Wouldn't the same effect have been had by doing what you suggested and putting magnets on the bottom of the poles?

Also, what's really the difference between a stacked humbucker, and a dual-tone single coil? Just the fact that the two coils don't cancel hum because of the way they're wound?

[David King]

Mike, thanks for explaining this so well. I didn't fully understand the design when I gave my initial, uninformed opinion. I always have an opinion and it's quite often wrong.