New Travis Bean Bridge Pickup. Quadcoils pickup?

[Tooth Of Davinci]

Hello to everyone!

I'm Enrico from Italy.
I'm happy to enter in this forum where I found very interesting tech informations about pickup winding.
Thanks for sharing all that.

I will go straight to the point:
I want build a new bridge humbucker pickup for my Travis Bean guitar.

In addition to the normal output I'd like to have another one for send the sound of the last 3 baritone strings for drive a bass amp.

For my poor knowledge this mean that I need to make a quad-coils pickup. Is it right?

In your opinion is all this doable with good results?

Suggestions and tech informations about quadcoils pickups are welcome!

Thanks in advance

[Tooth Of Davinci]

No answers???

[dpm]

Are you looking to send the bass 3 string to the bass amp at the same time as all 6 strings go to the guitar amp? Or do you just need to be be able to switch from a single 6 string output to dual 3 string outputs? I made quad coil pickups for an 8 string a while back so might have some useful tips. Here's a pic, I don't seem to have taken any of the construction details unfortunately

[Tooth Of Davinci]

Thanks Dpm. Yes I want send the bass 3 string to the bass amp at the same time as all 6 strings go to the guitar amp. Any useful tips are welcome!

[dpm]

I think the best way to approach it is with 4 side by side coils similar to a DiMarzio Multibucker (which is a Chopper and Fast Track 1 in a humbucker size package), the difference being that for your use 2 of the coils have shorter pole blades to only read the 3 bass strings. That way you can simply have 2 passive circuits, nice and simple. Kind of like this -

------xxxxxx
------xxxxxx
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Mojotone and possibly other places sell the appropriate bobbins and blade poles so there would be minimal fabrication involved.

[StarryNight]

here's a question: if the coil is going the length of all six strings but there are only blades under the three bass strings (or even magnet rods) would not some of the 3treble strings come through the signal as well? they may not be strong but perhaps at least the 4th string would be quite audible. I don't think Mojo sells humbucker parts for blade pickups but I could be wrong.

[David Schwab]

I'd just cut the bobbins the way dpm did. I'm doing that with a Jazz bass pickup at the moment. I'm going to wind one coil per string.

[StarryNight]

wow! I was so mesmerized by the guitar that I didn't see the cut line on the bobbins - very nice job! In that case perhaps try cutting the bobbins of a humbucker (super thin kerf!), wind 4 separate coils, join them together, wire the leads of the two butted bobbins together to create one output as well as taking separate leads for the bass coil out to another output. You might have to wire the butted coils together in parallel if they are to share the same polarity and humbuck with the other bobbin. If you use magnetic rods instead of a bar magnet you might be able to do some kind of humbucker thing by reversing the polarity of the bass strings.

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althought the middle strings might get some weird phasing :P

[David Schwab]

If you use magnetic rods instead of a bar magnet you might be able to do some kind of humbucker thing by reversing the polarity of the bass strings.

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althought the middle strings might get some weird phasing :P

Just make the top two coils S and the bottom two N, or vice versa. They can be wound and phased the same as if they were a continuous coil. Since the outputs will be from each pair, both will be humbuckers.

SSS|SSS
NNN|NNN

[dpm]

here's a question: if the coil is going the length of all six strings but there are only blades under the three bass strings (or even magnet rods) would not some of the 3treble strings come through the signal as well? they may not be strong but perhaps at least the 4th string would be quite audible. I don't think Mojo sells humbucker parts for blade pickups but I could be wrong.

Hard to say. If the magnet is also shorter I doubt it would become an issue. Mojo sell narrow blade bobbins ala Fast Track etc. and the blades too which could be cut shorter.

If you do use end to end coils David's suggestion of -

SSS|SSS
NNN|NNN

works best. On the construction side it's easy because you just use a standard magnet, but also I've found having opposing poles end to end leads to a noticeable dead spot between that effects the strings closest to it.

BUT

the reason I don't recommend doing it this way is that you'll end up with interaction between the bass amp and guitar amp input impedances in your application if you don't run multiple active buffer stages onboard. Doing it as separate pickups for each intended output is a lot less complicated, you can do it passive and get no interaction between the amps.

and

end to end coils don't leave much room for magnet wire. On that 8 string the polepieces are 3mm diameter (M3 bolts) to give enough room for a reasonable number of windings. And the coils are a little taller than typical for a humbucker for the same reason.

[dpm]

wow! I was so mesmerized by the guitar that I didn't see the cut line on the bobbins - very nice job!

Thanks! It does mess with the head a little. Obviously there's some Klein influence with the ergonomic aspect... it's a little Dali-esque to me with the conventional bass side melting into the leg rest treble side, and the frets of course.

[David Schwab]

BUT

the reason I don't recommend doing it this way is that you'll end up with interaction between the bass amp and guitar amp input impedances in your application if you don't run multiple active buffer stages onboard. Doing it as separate pickups for each intended output is a lot less complicated, you can do it passive and get no interaction between the amps.

It would be separate pickups since they have separate outputs. It doesn't matter that they are sharing the same magnet. And even if you got a little bleed going on between the bass and guitar sections, it's not like they are playing two different pieces of music! You wouldn't even notice.

[dpm]

Ah, but he wants all six strings going the guitar amp, plus just the 3 bass strings going to the bass amp.

[David Schwab]

Ah, but he wants all six strings going the bass amp, plus just the 3 bass strings going to the bass amp.

Oh! Well then he either needs a second set of pickups for the bottom strings, or he needs to run them into a mixer, and then send the low strings to left sand right channels and the high strings to the right. The bass amp can be in the left and the guitar amp to the right.

[dpm]

True that, with a mixer with High-Z inputs it would be possible to pan the treble string to one side of the stereo mix, while the bass strings stay panned center. That's another solution.

To do end to end coils with outputs connecting directly to the amps it looks like 4 preamp stages would be needed to stop them screwing with each other, as in the picture below. That 8 string uses MOSFET buffers for a similar application, though a TL074 based circuit would also do the trick.

The blade coil idea is simpler but it's possible the coils for just the bass strings might read a little of what the treble strings are doing.