stack jazz bass

[murof]

hello,

excuse my english....

i would like to build a 5 string jazz bass stack pickup set but i'm not sure that i understand how i have to build bobbins...

it's right like in picture? a coil in half magnets and the other one in the second half magnets?

how many turns about for a similar 5 string single jazz bass pickup?
thanks

bye

[David Schwab]

Yeah, that would do it.

You can try winding half of what I Jazz bass pickup is for each half, unless you are going to something else. My notes say 7,800 turns for a Jazz pickup, but I've also seen 8 or 9,000 turns listed.

You may also need to experiment a bit, and maybe wind the top coil more than the bottom.

I made two pickups like this. One for a Tele and one for a Jazz Bass. I haven't tried out the Jazz Bass, but the Tele sounds good, but is very bright.

This one had the magnets on the bottom of steel poles... probably not the best way to do it. Using rod magnets keeps the poles farther apart.

[David King]

You really don't want the same magnets going through rear coil at all. Make the bottom coil a dummy coil with wood dowels or steel slugs that DON'T align with the magnets above, or put a steel plate between the coils to redirect the field. If you run the magnets all the way through you have built two pickups that are out of phase (and hum-canceling). You will loose a lot of signal that way so you should wind a lot more turns to begin with and you probably need to use 43 or 44 AWG anyway. Tradition stacked coils are a really dumb idea.

I haven't done this yet so it's only my theory but no one has contradicted my so far. I'd be happy to find out otherwise.

[David Schwab]

You really don't want the same magnets going through rear coil at all. Make the bottom coil a dummy coil with wood dowels or steel slugs that DON'T align with the magnets above, or put a steel plate between the coils to redirect the field. If you run the magnets all the way through you have built two pickups that are out of phase (and hum-canceling). You will loose a lot of signal that way so you should wind a lot more turns to begin with and you probably need to use 43 or 44 AWG anyway. Tradition stacked coils are a really dumb idea.

I haven't done this yet so it's only my theory but no one has contradicted my so far. I'd be happy to find out otherwise.

Duncan's first stacks have the magnets going all the way though, which is why i tired it this way. The one thing is the bottom coil isn't as sensitive to the strings as you would think, and has a much darker tone. By having the magnet poles at opposite ends, you sort of have the coils facing away from each other. But you do have phase cancelation of the low end, which is why these kinds of stacked pickups are so over wound.

I didn't pursue working on that pickup, but a quick test seemed to sound OK. It had two ceramic magnets facing the rods the way a P-90 is set up. The same design, but with a blade, was used for a Tele lead pickup for my set neck Tele/LP hybrid. That gets a very clean bright tone with plenty of output. I wound it to about 12K. But it lacks low end. Switching the coils in phase produces a very loud and bassy non hum canceling pickup.

The trick seems to be what Kinman, DiMarzio and Duncan are now doing with the bottom coil having no magnets, but having a lot of metal in it. In the case of the DiMarzio Virtual Vintage Solo Pro I had in my shop, the top coil was wound a lot higher than the bottom coil, which is setup to just collect hum, and the extra metal helps by raising the inductance on that bottom coil. Then the two have the magnet shield between them.

Possum had suggested to me back when I first did the tele pickup to experiment with winding the two coils mismatched. I think that would bring out more low end when you have the poles running though both coils.

Even with the dummy coil, you will lose some output, unless you do an active system.

[Stan H]

Yeah, that would do it.

You can try winding half of what I Jazz bass pickup is for each half, unless you are going to something else. My notes say 7,800 turns for a Jazz pickup, but I've also seen 8 or 9,000 turns listed.

You may also need to experiment a bit, and maybe wind the top coil more than the bottom.

I made two pickups like this. One for a Tele and one for a Jazz Bass. I haven't tried out the Jazz Bass, but the Tele sounds good, but is very bright.

This one had the magnets on the bottom of steel poles... probably not the best way to do it. Using rod magnets keeps the poles farther apart.

I would've thought you would split the difference of the windings of a "normal" pickup. Is there a ratio that you go by when doing one of these, David? Also, if they are missmatched will that induce noise thus defeating the purpose of the dual coils?

[David King]

Stan,
matching coils for CMRR is more complicated than just the number of turns, the formula also involves surface area of the coils and the magnetic density* of the core.

http://en.wikipedia.org/wiki/Common-...ejection_ratio

*Magnetic density isn't the correct technical term but I can't think of it right now.

[Stan H]

oh....

[David Schwab]

I would've thought you would split the difference of the windings of a "normal" pickup. Is there a ratio that you go by when doing one of these, David? Also, if they are missmatched will that induce noise thus defeating the purpose of the dual coils?

I said that because I'm used to working with regular side-by-side humbuckers...

With Stacks, a lot of them are equal on both coils, like the first Duncan pickups, and EMG's too. EMG Strat pickups just have the bar magnet in the core of the bobbin, and two equal sized coils.

The problem with stacked pickups with two active coils is the two coils are wired out-of-phase, and they cancel out a lot of the low end, just like two out-of-phase coils do. Side-by-side humbuckers pick up the strings in a differential manner, because of the opposite magnet polarities.

But part of a common pole stack pickup is between the magnet poles.

So in this style of pickup, mismatching the coils can improve the low end without causing too much noise. I recently did a side-by-side humbucker mismatched by 1,000 turns. I got the idea from an old Hi-A pickup. It didn't seem any noisier than the same pickup with matched coils.

The DiMarzio Virtual Vintage pickups use the idea of having less turns on the bottom coil, but it's also higher inductance, so it needs less turns. You can also make it larger in diameter than the top coil, which will increase it's surface area and noise sensitivity. The ideal situation is the bottom coil doesn't sense the strings at all, just noise, and the top coil senses both.

That's the idea of a dummy coil. The problem with dummy coils in a passive setup is that they load the string sensing coil and alter its tone.

I think there still a lot of room to try out ideas with stacked single coils. A recent patent application has each coil with magnets, and the magnets are oriented with the same poles facing each other in the middle, which is also how the Les Paul Recording pickups were made, except that they had a steel plate between them.

I'm working on some Jazz bass pickups, but I'm avoiding this whoe thing by making them side-by-side humbuckers like the Joe Barden's.

[Stan H]

My current most popular bass pickup is my Split J Set which is an inline humbucker like the Nords. I have a customer that is interested in a stacked Tele Lead pickup and I've never done a stacked pup before...just trying to get a handle. Guess I should just experiment a bit. Thanks for the info!

Sorry for hijacking your thread, murof.

[David Schwab]

The split pickups work great for bass. When you start bending strings between coils, like if you made a split Strat pickup, then you have a problem!

I had some old Dimarzio Model J's and the Schaller versions, in a few basses in the past.

That's probably the best way to do it. Gets messy when you have an odd number of strings, like 5 string basses, but winding the same number of turns, even if the bobbins are different sizes, works well.

[Stan H]

I had some old Dimarzio Model J's and the Schaller versions, in a few basses in the past.

Yeah, I have an old Kramer Duke bass with the Schaller Double J pickup. It's actually two split J's under one cover (4 coils & 8 leads). That's where I got the idea, even before I saw the Nords.

[David Schwab]

Yeah, I have an old Kramer Duke bass with the Schaller Double J pickup. It's actually two split J's under one cover (4 coils & 8 leads). That's where I got the idea, even before I saw the Nords.

I had an early Duke with a crappy Schaller Bassbucker (DiMarzio Model G clone).

That was before I was winding, but I made two steel blades for it and unwound some wire. It was a bit better then.

I did the same with a Model G, but left it fully wound, and it made a great guitar pickup, since it's just an X2N without the big blades.

[Stan H]

One last quick question about the stacked bucker. Would you wind both coils in the same direction and tie the finishes just like a regular humbucker? Well, I guess in the case of a "single coil" you would probably tie the starts to keep the hot away from the mags...

[David King]

I think I would wind one reverse and use the starts as my hots so the outer wraps can act as a shield. If I were going over 7-8k I'd hook them up in parallel but I don't know nothing about them yet.
Are you afraid of starts shorting to your magnets? You need to eliminate that possibility.

[Electricdaveyboy]

Hello!
Here is a pic of the noiseless stacked pickups I do.It shows the plain bobbin unwound.
I use the magnet in between the top and bottom coil like seen on the P-100.
This makes the polepieces south (or north) and prevents from magnetic shorts.
Both coils are wound same direction and wired end to end in series.I use 1mm black fiber for the top and bottomplates an 2mm for the elevator.
The shorter the steel polepieces the better the tone.

peace,
david