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coil tapping humbuckers

#21
I'm a proponent of the split coil humbucker, and my favorite pickups are the MM-style. I have 2 basses to which I have done this, and I enjoy them just that much more.

However, these basses are Active and I feel that with a Passive bass, you may want to stick with Parallel and Split coil only, and forgo the Series wiring.

As has been pointed out, Series wiring yields a higher output than split coil and parallel, and switching between series and the other two would crate some problems when playing live. ON an active bass, you can adjust for output loss with your on-board eq, but with a passive bass, you'd have to go fiddle with your amp.

About a year ago, I modded a Squier Jazz with dual MM-style pickups and stayed with Parallel/Split coil wiring for that reason.

As far as the tone difference between parallel and split coil, they are very different...at least with the pickups that I have. I find that Parallel sounds more like Series, and with an active circuit being able to compensate for volume increase/decrease, you can make the 2 sound identical.

Here is a video I just made, with my single-humbucker Dean Sledgehammer 5, using the stock ceramic-magnet MM-style humbucker. When the coils are split, the North coil (the one towards the neck) is active.
I start out in Parallel mode, then switch to Split Coil and then to Series. The camera doesn't seem to really pick up the volume increase with Series (then back to split & parallel), but you can sort of hear the difference between split coil and the others. Set the volume on the highers side of things to really hear the difference. You'll also notice the single coil hum.



The Split coil mode gives a big openness to the sound. Parallel & series sound more tightly focused.
(amp is a Carvin BX500 and an old SWR 1x12 cabinet)
 
#23
line6man said:
Series is the standard for most humbuckers, MM pickups being the exception.
Click to expand...

MM pickups were intended to be low impedance. That's the way they advertised them when the bass was introduced. They are really medium impedance. They aren't wound too hot, and then wired in parallel. That's also also why they used a preamp with that bass.

I guess Leo just wanted to do something different for that bass.

:)

Most humbuckers are designed to be wired in series. You can wind them hotter with the intention of using them in parallel. That works better for splitting. A better trick is to wind one of the coils with a tap. That way when you switch into single coil mode, you engage the extra windings, and get the sound of a regular single coil, instead of half a series humbucker.

But yes, MM pickups are the exception. They are humbuckers, but not a typical design.

Personally I don't use single coils at all because of the noise.
 
#24
I'm pretty much talking about any aftermarket MM-style pickup with 4 leads. You can wire them any way you want. Some are designed for Series wiring (the Carvin pickups I have), but you can do parallel. SD MM-style pickups are designed for Parallel wiring, and they show you how to wire it any way you want.
http://www.seymourduncan.com/images/products/basslines/501040-110.pdf

Original MM pickups (stingray) have 2 leads and are wired in parallel internally, so you can't really split those coils too easily (but it is possible)

Now I'm not trying to start anything with you guys who know much more about pickups than I do. I'm just stating my opinion on this subject and citing where I'm coming from. That's all.
 
#26
eastcoasteddie said:
I'm a proponent of the split coil humbucker, and my favorite pickups are the MM-style. I have 2 basses to which I have done this, and I enjoy them just that much more.
<...>
As has been pointed out, Series wiring yields a higher output than split coil and parallel, and switching between series and the other two would crate some problems when playing live. ON an active bass, you can adjust for output loss with your on-board eq, but with a passive bass, you'd have to go fiddle with your amp.
<...>
As far as the tone difference between parallel and split coil, they are very different...at least with the pickups that I have. I find that Parallel sounds more like Series, and with an active circuit being able to compensate for volume increase/decrease, you can make the 2 sound identical.
Click to expand...

Yeah, normally that's the case, the two coils have outputs that are correlated and sum directly, so the series output will be exactly 6 dB (decibel) hotter than the parallel or single-coil arrangement.

To my ears though, the parallel, series, and single-coil options all sound distinctly different.

But it's possible to compensate for this volume change with a small circuit so that you have essentially constant volume for all three options. I've done it on my Musicman SUB5 (active) bass with a parallel/single/series switch mod. I don't know why more manufacturers don't add a similar compensation network (maybe MM does). Haven't found any circuit anywhere on the web that shows how to do this, and (while I am an Electrical Engineer) really doubt that I'm the first person to ever figure this out and design this circuit. It's just some clever usage of Thevenin's Theorem and some hours of empirical testing to get the exact values to pair with a given pickup. The circuit values are extremely touchy to get it exact though.

I've only done this mod on one bass, and its preamp is always in the circuit, so both pickup output impedance and preamp input impedance are constant, perhaps the volume compensation can't be quite as exact on a passive bass that plugs directly into different amp inputs with different input impedances. I'd have to experiment more to figure that out. But still, manufacturers could put in a circuit to do this and at least be *closer* on a passive bass than having a big 6 dB jump in volume between settings.
 

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