Connecting 4 coils in Humbucker mode

[Phil m]

I'm building an extended range bass, 9 strings. I just started designing the pickups this week and ended up with a problem. I originally wanted to build two humbuckers, 1 in bridge position and 1 in neck. Both buckers would have had the normal two single coils in RWRP.

My problem is that the neck bobbins need to be 6 1/2" wide while the bridge one 6 3/4". The stewmac forbon is 6"X 6"

So I've decided to split the single coils into two side by side coils, 5 treble strings on one coil and 4 lower strings on another.

I want to have the whole humbucker thing connected in series. How would I go connecting the whole thing?

For an example and to ease the whole thing here is a picture of, let's say, the neck bucker.



This is what I'm thinking of doing. Keep both treble side bobbins north side and both bass side bobbins south side, connect each one of them in series with their treble or bass counterpart and wire those two buckers into series.

Any idea if that would work? How do you connect two buckers in series since you already have RPRW on both coils?

[Phil m]

Wow, 38 views and not one reply

Maybe this question will be less complicated. I've been thinking, instead to keep both split coils connected in series in the same winding direction and same polarity. So the top two coils would be technically one large north side single coil split two ways and the bottom one, same thing but north side wound. Connect the two "split single coils" in RWRP.

Any reason why this wouldn't work?

[David Schwab]

You have two choices, Either make two humbuckers next to each other, one for the 5 strings, and the other for the four, or wire up the top two coils as one coil, and the bottom two as the other.

I'd probably do the latter. But if you do the former, you have the option of splitting it so you have a P pickup style humbucker for a different tone.

[mkat]

That's a good option David. I was thinking of wiring them up as two single coils. However, if the coils are split like Phil's diagram, it seems to me that these could be wired via switches to give the following:

- pbass config
- single coil jbass config
- dual coil humbucker (ofcourse)

Just on the pbass config. With a pbass, the pickup is placed in a location where it will pickup the fattest sound. I'm not sure how they'll sound closer to the neck or back near the bridge.

[Phil m]

Thanks for that. I'll probably do the second option. I don't have any more space for switches in the cavity, It's already got a 3 band preamp + mid-switch. Series humbucking is plenty for now.

[Phil m]

I'm just bumping this thread to personally thank the two forum members who have offered me, through PM's, forbon pieces large enough to solve my original problem.

You two know who you are. Thanks very much to you guys and to this forum for getting such a great group of pickup builders together

[David Schwab]

Series humbucking is plenty for now.

I use 4 conductor wiring on my pickups, and I have yet to install any series parallel switches! I listened to them with one coil off, and in single coil mode they didn't sound much different... I might try parallel next, but I like series better.

[mkat]

I use 4 conductor wiring on my pickups, and I have yet to install any series parallel switches! I listened to them with one coil off, and in single coil mode they didn't sound much different... I might try parallel next, but I like series better.

That's interesting and nice to know. Are your pickups passive? Also, was there a difference in output rather than sound? It looks like Phil is working with the specs from a standard jbass coil as a base.

I just made a set of dual coil humbuckers for bass with 4 conductor wiring but haven't tried them yet. I haven't drilled for switches yet either, so I might just wire it all up and test before I make a decision.

[David Schwab]

That's interesting and nice to know. Are your pickups passive? Also, was there a difference in output rather than sound? It looks like Phil is working with the specs from a standard jbass coil as a base.

They are passive, but low/medium impedance. So they are very low output and need a preamp. I'm sure there would be a difference in parallel, but they are already very bright, so I don't see the point in it.

But still I used 4 conductor wiring so I have that option. I'm planning on adding a couple of switches to my bass to try it out.

[dpm]

Phil, I'm in Brisbane and have a couple of big sheets of Forbon I can cut down to suit. Seems you're getting the stuff thrown at you now lol

[Phil m]

Brisbane, really? We should meet up. Did you get the forbon locally?

[dpm]

I got it from Melbourne, details in the 'Alternative to Forbon' thread... http://music-electronics-forum.com/s...0&postcount=42

I don't know if I'll be needing any of what I've got as I'm trying ABS instead.

[David Schwab]

I don't know if I'll be needing any of what I've got as I'm trying ABS instead.

Let us know how that works out. I have a few sheets of polystyrene I'm about to try out.

[dpm]

I got around to assembling some coils today, some 8 string forbon and much longer 9 string ABS (2mm thick). The ABS is so much easier to deal with - it's flat and stays that way It is more flexible but once the mags are in that isn't an issue. Not brittle in any way, looks good.

Back on topic, this project of Phil's is very similar to a bass pickup I had wound recently (the design and parts were up to me, it was wound elsewhere). The pairs of coils were wired in series end to end and then in parallel like two J pickups as David suggests. These are the only photos I got of it unfortunately. you can see how the base plate allows for the cables to exit. The bobbins are essentially the same as your design, just round on the ends. The end result was fantastic IMO

[David Schwab]

That's a great looking bass. The pickup is pretty cool as well. I have yet to play one of those fanned fret basses.

What's the two scales involved?