Wiring help please? Push/Pull humbucking/single coil with EMG Hz

[Chris Wilke]

Hi TBrs!

I have a Spector Rebop 5 with EMG Hzs, and I would like to add Push Pull pots for each pickup. I am trying to switch between Humbucking (series) and Single Coil. I would like the inner coils to be active in single coil mode (giving me a parallel humbucking mode with one coil of each pickup when both are in single coil mode, approximating a MM stingray sound by my calculations).

I have searched around and found the basic diagram for Coil Splitting with a push pull pot, but I cant find a diagram for two pots, "soloing" opposite coils on each pickup. The wiring would have to be different for each pot/switch, otherwise I'd end up with two North coils or two South coils which is not what I want.

There are so many diagrams out there, its amazing that I cant find the specific one I am looking for!

Thanks for any help!

Chris

 

[dwizum]

EMG has an instruction sheet that shows a schematic of the pickup:

Invalid Link Removed

The pins are:

green (front coil -)
white (front coil +)
ground
red (rear coil -)
black (rear coil +)

A typical humbucker configuration would tie the black and white wires together, use green as ground, and red as the signal. If you follow the signal path from ground to hot, it goes from the minus (start) of the front coil, through the front coil, then from the + of the front coil to the + of the rear coil, through the rear coil "in reverse" and out the - of the rear coil. The magnetic polarity of the two coils is opposite, so you end up with two coils that are opposite magnetic polarity and also opposite "direction" in terms of the orientation of the coil.

This is humbucking (noise cancelling) because noise doesn't "see" the magnetic orientation, only the coil direction. So from a noise perspective, the two coils being opposite of each other means the noise signal in each coil is opposite in phase, so it cancels itself. Meanwhile, the signal gets through because from the vibrating string's perspective, the magnetic polarity also impacts the polarity of the signal - so, the two opposites (magnetic and coil direction) cancel each other, and you end up with a signal in each coil that are in phase, as if there was just one big coil - the two small coils put in series.

When we want to split a humbucker and get one single coil to act like a single coil pickup, it's helpful to think of the pickup as having a bottom (the wire connected to the middle), a middle (the tap, aka the two wires tied together), and a top (the wire that's connected to signal). You can "coil tap" or split the pickup by connecting the middle to either the top or the bottom.

A typical coil split on a single pickup works by shorting the two joined wires at the middle (the black and white wires in your case) to ground. What this does is bypass the front coil, since the signal's path from ground now goes straight to the black wire, through the rear coil, and out the red wire. The front coil basically gets skipped, since electricity takes the path of least resistance, and both ends of the front coil are tied to ground.

Since you expressed that you want the two inner coils active for your coil split, that typical approach of grounding the tap at the middle of the pickup will work for your neck pickup. The "rear" coil that's left active will be the innermost coil on the neck pickup.

For the bridge pickup, to activate the inner coil, you want to do the reverse. You want to cut the rear coil out of the signal, instead of the front coil. To do that, you want to lift the black/white connection to the red wire instead of pushing it down to ground.

Look at typical wiring diagrams for using a push pull switch to do a coil split. When you're splitting a single pickup with a typical push pull pot, the wiring is very simple. You connect the middle pair (the tap) - the white and black wires in your case - to one terminal of the switch, and you connect the thing you want to short it to to the other terminal of the switch. If you're looking at a push/pull pot as you would from the back of the bass, with the pot down and the switch contacts up, typically you'd wire it like this:

I clipped this out of a larger diagram. You can ignore the labels on the wires. The "north finish" and "south finish" are your black and white pair. "South start" is your green wire, and "north start" is your red wire (which, of course, would be connected to the rest of your wiring, not left hanging like in my clip here). In this diagram, the switch would short the black/white pair to ground when it's pulled. So, you can use this for your neck pickup.

For your bridge pickup, you'd do the same thing - connect the back and white pair to the middle terminal on the push pull switch. But instead of connecting the bottom terminal to ground, you could connect it to the red hot wire from your pickup. That way, when the pot is pulled out, the black/white pair are shorted to the signal wire and the "front" coil is left active.

That's very long winded but hopefully it helps.

 

[Chris Wilke]

This helps a lot thank you so much!

I was just about there in thinking through this, but you confirmed a lot for me. The last thing is how to connect the tabs on the pots. These are the conventional terminals not the switching terminals. Right now I am planning to wire the right tab to ground and the the left tab becomes the signal, eventually going to the hot lead on the preamp (?)

This means nothing connected to the center tab of either pot. Or am I missing something?

EMG has an instruction sheet that shows a schematic of the pickup:

Invalid Link Removed

The pins are:

green (front coil -)
white (front coil +)
ground
red (rear coil -)
black (rear coil +)

A typical humbucker configuration would tie the black and white wires together, use green as ground, and red as the signal. If you follow the signal path from ground to hot, it goes from the minus (start) of the front coil, through the front coil, then from the + of the front coil to the + of the rear coil, through the rear coil "in reverse" and out the - of the rear coil. The magnetic polarity of the two coils is opposite, so you end up with two coils that are opposite magnetic polarity and also opposite "direction" in terms of the orientation of the coil.

This is humbucking (noise cancelling) because noise doesn't "see" the magnetic orientation, only the coil direction. So from a noise perspective, the two coils being opposite of each other means the noise signal in each coil is opposite in phase, so it cancels itself. Meanwhile, the signal gets through because from the vibrating string's perspective, the magnetic polarity also impacts the polarity of the signal - so, the two opposites (magnetic and coil direction) cancel each other, and you end up with a signal in each coil that are in phase, as if there was just one big coil - the two small coils put in series.

When we want to split a humbucker and get one single coil to act like a single coil pickup, it's helpful to think of the pickup as having a bottom (the wire connected to the middle), a middle (the tap, aka the two wires tied together), and a top (the wire that's connected to signal). You can "coil tap" or split the pickup by connecting the middle to either the top or the bottom.

A typical coil split on a single pickup works by shorting the two joined wires at the middle (the black and white wires in your case) to ground. What this does is bypass the front coil, since the signal's path from ground now goes straight to the black wire, through the rear coil, and out the red wire. The front coil basically gets skipped, since electricity takes the path of least resistance, and both ends of the front coil are tied to ground.

Since you expressed that you want the two inner coils active for your coil split, that typical approach of grounding the tap at the middle of the pickup will work for your neck pickup. The "rear" coil that's left active will be the innermost coil on the neck pickup.

For the bridge pickup, to activate the inner coil, you want to do the reverse. You want to cut the rear coil out of the signal, instead of the front coil. To do that, you want to lift the black/white connection to the red wire instead of pushing it down to ground.

Look at typical wiring diagrams for using a push pull switch to do a coil split. When you're splitting a single pickup with a typical push pull pot, the wiring is very simple. You connect the middle pair (the tap) - the white and black wires in your case - to one terminal of the switch, and you connect the thing you want to short it to to the other terminal of the switch. If you're looking at a push/pull pot as you would from the back of the bass, with the pot down and the switch contacts up, typically you'd wire it like this:

View attachment 4134233

I clipped this out of a larger diagram. You can ignore the labels on the wires. The "north finish" and "south finish" are your black and white pair. "South start" is your green wire, and "north start" is your red wire (which, of course, would be connected to the rest of your wiring, not left hanging like in my clip here). In this diagram, the switch would short the black/white pair to ground when it's pulled. So, you can use this for your neck pickup.

For your bridge pickup, you'd do the same thing - connect the back and white pair to the middle terminal on the push pull switch. But instead of connecting the bottom terminal to ground, you could connect it to the red hot wire from your pickup. That way, when the pot is pulled out, the black/white pair are shorted to the signal wire and the "front" coil is left active.

That's very long winded but hopefully it helps.

 

[dwizum]

What pots are you talking about? And what functions are they for?

 

[Chris Wilke]

These are the pots:
Alpha Push-pull Pots | stewmac.com
These are my volume pots. For a two humbucker V V T B set up (no pickup switch, no tone control).

To revise my earlier question, which I see now is wrong...I take it the right tab is the ground, the center tab is essentially the input and the left tab is the output? If so, would I just connect the hot lead from the pickup to the center tab and take the left tabs from each pot in parallel to the input (hot lead) on the preamp?

 

[dwizum]

Just to clarify - If you're using a push pull pot, the switch portion is 100% separate in function from the pot itself. You just wire the pot exactly like you'd wire any other pot in any other bass, for whatever function you wanted.

So if you're using those as your two volume pots, you just wire them like you'd wire any volume pot. Typically, the pickup's hot lead would go to the left terminal, the middle terminal would go to your ouput (your preamp or jack's input), and the right terminal gets grounded.

 

[Chris Wilke]

Report Back -- Success!
So after several misteps and a couple bonehead mistakes (one that almost melted my 9v battery) the project is complete! 2006ish Alder Spector Rebop 5 DLX with EMG Hz now with switching for each pickup to both Humbucking and Single Coil modes. Big thanks to dwizum for advice here and to Spector for having Tone pump wiring diagram on their website. (I will add another post for a volume control question below)

Bottom Line- I am very happy with the results... Happy NBD, of sorts! The EMG 40Hz Soapbars sound quite good in single coil mode and between the two pickups and two switches, the combinations are almost endless. I had debated for a while on whether to do series/parallel or humbucking/single coil and I landed on adding single coil modes. Clearly brighter and more articulate in single coil while fatter and fuller in humbucking. Grind and growl for days, with an upper midrange presence that can be called up for a sound not unlike a classic Alembic (especially in mid-upper registers). This bass is not "scoopy" unless you want it to be. I know not everyone loves the EMG Hz pickup (some say muddy? but this bass is anything but).

The layout is V/V/Tr/B with the original non-trim tone pump pre. Each volume control is pull for single-coil mode, push for humbucking mode. I am amazed at how quiet it is. I don't detect ANY 60 Hz hum in single-coli settings and it gives the Rebop even more jazz bass flavor IMO. I chose the inner coils for activating a parallel humbucking mode when each for each pickup is in single-coil setting at equal volumes. The idea was to cop a Music Man tone as much as a fender jazz, and I think it lies somewhere in between, but maybe closer to a jazz. The bass is now a little on the bright side but with brand new strings I expect it to settle in. I may try flats when these wear out.

There is a slight drop in volume in single coil mode that you need to compensate for if you switch up the tone but want to keep your volume the same. My (now fretless) Music Man StingRay 5 solves this in the pre somehow.

With dual pickup basses, I always tend to favor one pickup over soloed pickups/ equal settings in both, and so when I have one pickup in Humbucking and the other favored in single coil I have to back off the humbucking one a little more than usual. When favoring the humbucker over a single coil, they both can be wide open.

My favorite setting is with the Neck pickup in HB mode at about 60-70% and the Bridge pu wide open. Bass and Treble each sitting about 3-4/10, which is fairly close to neutral settings on the tone pump I think (there is no center detent on the tone pots and they are not true boost-only either, as they are commonly referred to).

FYI I got this whole idea from some of the Spector Euro basses which use Active EMGs instead.

New Jazz Bass GAS averted (for now)

 

[Chris Wilke]

OK Here is the volume control question I alluded to in the previous post. In researching dozens of wiring diagrams (many for guitar) I noticed most have the hot lead coming into the volume pot left tab, and the output leaving via the center/sweeper tab. This is referred to as Les Paul wiring (sans switch in my case)

Jazz Bass wiring brings the leads from the pickup to the center tab from the pot, and the signal leaves via the left tab, with the 2 volumes in parallel. Right is ground in both cases

I was not aware of this distinction and I followed what I later learned was the Les Paul system as that seemed more common. I found one significant artifact of this: When one pickup is all the way off (or less than say 20%), it functions as a kill switch for both pickups (on a Les Paul assuming the 3-way switch is set to both). Unless you have a 3-way switch you can't solo pickups. I never knew this was a thing. I thought I had done something wrong at first, but I guess Les Paul guitars are all this way? Like most basses my bass does not have a switch.

Anyway, as I said in my previous post I was quite happy with the results and since I don't generally solo a pickup I am going to keep it this way. Plus, I now have a kill switch (mute button)!

Even with a straight J bass wiring, in practice I have found if one pickup is below 50% the output doesn't sound much different, than if it was all the way off. And I tend to like favored settings rather than soloed settings anyway.

What do others think? Anyone running a two pickup bass in "Les Paul mode"? I imagine there must be some effect on the sound...is there? Or is this just dumb and should I switch it?

 

[Joblivion]

Do the series/parallel pots work on bass pickups? I noticed it is the same connection type for Hz style pickups and I may get a bass with two Hz soapbars.

Invalid Link Removed

 

[dwizum]

They will work for any EMG pickup with the matching wiring harness (4 conductors and a ground). They're 500k pots though while most people would use 250k pots on a bass. It'll work fine but it'll be brighter in tone.

 

[Chris Wilke]

They will work for any EMG pickup with the matching wiring harness (4 conductors and a ground). They're 500k pots though while most people would use 250k pots on a bass. It'll work fine but it'll be brighter in tone.

Yes, indeed: series/parallel, OR series/single-coil switching is possible with any 4 conductor humbucking pickup. Some HB pickups just have 2 conductors and do the series or parallel thing internally and these do not permit external switch (at least not w/o modification to 4-wire).

 

[Frank Barroso]

Does this work for EMG 45hz?