multi-gauge wire humbucker question

[belwar]

It is not the number of turns, it's the area-turns count. That is the basic rule, absent any nearby iron. The "area" is that bounded by the turn in question. In practice, we use the average area of turns, and multiply by the turns count, and it's close enough.

Note that the inductance is not the issue, it's the area-turns product, which controls the voltage generated by a coil immersed is a uniform changing magnetic field. The difference is that the inductance varies as the square of the turns count, while the area-turns count varies linearly with the turns count.

Joe - Do you have any good resources to learn more about area-turns product? Are you aware of any matematical way to calculate this measurement? I would be great to be able to have a formula to calculate "approximate" required measurements for hum cancellation when dealing with multigauge.

[big_teee]

Joe - Do you have any good resources to learn more about area-turns product? Are you aware of any matematical way to calculate this measurement? I would be great to be able to have a formula to calculate "approximate" required measurements for hum cancellation when dealing with multigauge.

But don't you find anything in the general ball Park to be pretty much Hum canceling?
I Make what I call a Hybrid. I wind the screw bobbin Fairly full with 42SPN, and about all I can get of 43 SPN on the Slug Coil.
Not sure on the turn count, but pretty sure highly mismatched in favor of the 43GA.
It is nearly as quite as my 7.2k Symmetrical Wound Neck Pickup?
What is your Experience?
Terry

[belwar]

sure I could just start winding and try, but i'd like to try to get an understanding of why/how it is functioning. I'm having a difficult time understanding the "coil area".. Trying to remember back to my high school math class, I thought that area was a two dimensional measurement - So in a three dimensional coil, what area is it measuring?

The area around the core? i.e. a top down view?
one side of a side view?
Front view? (clearly unlikely)

I'm dumb as a cork, but I want to learn

[frankfalbo]

Hopefully someone chimes in with a mathematical answer that satisfies you. In the mean time I find the rudimentary way to consider it is simply as an audio condition rather than a mathematical one. You have two signals summing. They don't phase cancel the audio, just the hum. So for hum cancellation perfection all you need is for each coil's noise to be as loud as the other's. Turn count is only one way to affect that. Creative shielding and purposeful ground or float decisions for each component can fine tune the noise level as well.

[David King]

Bel,
I'll try to reply with a little more clarity. You are correct, you want to measure the top-down, 2 dimensional window through the coils, and yes, area is the width times the length of the bobbin core. As each layer of wire piles up on the bobbin, it takes in a slightly larger area. You can figure out the average area of each coil by measuring the area window through the layer that sits exactly half way through the wind. If you wax potted the 2 coils and sliced each off the bobbin and then peeled each apart right at the middle layer, you could lay those outer layers side by side (but reassembled and maintaining their former, oblong shape) and hopefully see that the 43 awg coil is the same percentage smaller in window area as the difference in wire diameter times π i.e. the wire cross section. (2πr is the area of a circle, the wire is round). To mathematically find the area you can break the coil shape into 3 parts, a half circle at one end, a rectangle in the middle and an identical 1/2 circle at the other end. Now we can presumably ignore the rectangles because they're going to be the same length on both coils and their widths are the same as the diameter of the two half circles from each coil. If I were really good at geometry I could pull the theorem out of my butt and prove to you that the difference in wire diameter is going to be the same as the difference in coil area between your 42 and 43 wire cross-sections. I absolutely stink at geometry and have no idea if that's actually true, right now it's a strong hunch.
I looked up on a table that AWG 43 = .0025 mm^2 and AWG 42=.0029 mm squared . I divide 29/25 = 1.16 or that for every 100 turns of 42AWG you might need 116 turns of the 43 to get to the same size coil. I don't think we need that many extra turns to equalize turns areas, I'm guessing we need about 1/2 as many or 108 turns but I can't tell you why.

Someone with better 8th grade math needs to come in and save me here.

[fieldwrangler]

So, I put one of my very-well-matched two-coils-on-the-same-axis pickups on my main axe and it seemed to hum a lot more than I would expect.

So, I figured maybe it wasn't as well matched as I thought and put in another one. Same deal, and the neck pickup was still dead quiet (it,in fact, is using two different gauges of wire on the coils.)

So, while I was scratching my head about this my eyes went over to this big honkin' piece of metal a half-inch away from the pickup (namely the integrated bridge/tailpiece on my Melody Maker) and I began to wonder if its proximity to one coil could explain this phenomenon. I haven't yet done any of the obvious tests yet, and I need to leave for a trip early this morning.

So, before I do test for this, whaddya think?

Bob Palmieri

[NPB_EST.1979]

I just wound some stewmac humbuckers both around 9k... screw bobbin with 42 awg 5000 winds and slug bobbin slightly overwound 5400 or so winds with 43 awg and covered with gold cover and AllStar Magnetic Alnico II. Made the mistake of not wax potting again after I put the covers on, so bridge was pretty feedbacky, and I had to take he cover off. I think the bridge was a little too thin and strident... need to come up with a warmer recipe, but a fine experiment!

[big_teee]

I just wound some stewmac humbuckers both around 9k... screw bobbin with 42 awg 5000 winds and slug bobbin slightly overwound 5400 or so winds with 43 awg and covered with gold cover and AllStar Magnetic Alnico II. Made the mistake of not wax potting again after I put the covers on, so bridge was pretty feedbacky, and I had to take he cover off. I think the bridge was a little too thin and strident... need to come up with a warmer recipe, but a fine experiment!

Try a full Screw coil of 42 & a full slug coil of 43, with a A2 as strong as you can get it.
It sounds great, I have one in my LP Copy.
I have that in the bridge, and a Symmetrical A2 in the neck, IMO they sound great together.
B_T

[David Schwab]

So, I put one of my very-well-matched two-coils-on-the-same-axis pickups on my main axe and it seemed to hum a lot more than I would expect.

So, I figured maybe it wasn't as well matched as I thought and put in another one. Same deal, and the neck pickup was still dead quiet (it,in fact, is using two different gauges of wire on the coils.)

Do you have the coils wired in phase?

[David Schwab]

If you had 5000 turns 42 and 5000 turns 43 is that equal in Hum reduction?

Yes, it will hum cancel.

I usually do highly mismatched coils and hope for the best.

What are you trying to achieve with the mismatched coils? More treble?

[fieldwrangler]

Definitely.

I'm planning to check out the hairbrained idea that maybe proximity to the bridge is unbalancing the thing this weekend.

[David Schwab]

Definitely.

Definitely in-phase? Humbuckers are wired out-of-phase. That might be why its humming. Either that, or it doesn't know the words.

Wire them start to start, or finish to finish, wound the same direction.

I'm planning to check out the hairbrained idea that maybe proximity to the bridge is unbalancing the thing this weekend.

Many of my bridge pickups use multi gage wire. That's not the issue.

[big_teee]

OverWound Bridge P/Us do seem to pickup more noise and are more sensitive, and have more gain, than a low wound neck P/Us.
Some Amps are way more noisey than others.
IME Head Amps are usually quieter than Combos.
B_T

[David Schwab]

OverWound Bridge P/Us do seem to pickup more noise and are more sensitive, and have more gain, than a low wound neck P/Us.

Maybe because they are overwound? (i.e. louder?)

I'm not sure we are talking about overwound pickups here. Either way, even over wound humbuckers should be quiet.

[fieldwrangler]

Definitely in-phase? Humbuckers are wired out-of-phase. That might be why its humming. Either that, or it doesn't know the words.

Wire them start to start, or finish to finish, wound the same direction.

Well... in this case they're sidewinders. I've been winding these for 20 years (perhaps almost as long as you!) and I actually connect them in electrically in-phase series (head to tail) but point them in opposite directions. Not that there's not a big chance of me screwing up, but if I had done so I'd notice a quite unexpected timbral quality before the hum thing became apparent.

Many of my bridge pickups use multi gage wire. That's not the issue.

And in fact, my neck pickup (also a sidewinder) is also a multi-guage unit and is nearly dead quiet.

By the way, this "sidewinder" term is something I learned from you, and is much more convenient than my previous "horizontally opposed coaxial" monicker.

Bob Palmieri