Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both?

[krm27]

I did a project a couple years ago, installing two P-Rails in an old neck-thru guitar. After starting to install triple-shot rings and deciding I hated them, I decided instead to add four push-pull pots, under the tone & volume knobs, which let me set each P-Rail in any of the four settings (single coil, P90, series humbucker or parallel humbucker). The guitar also has a 3-way switch to move between bridge, neck or both pickups (basic Les Paul type of controls).

There is no humming in either humbucker mode. There is noticeable humming in P90 or single coil mode if I'm using only one pickup (bridge or neck). However, the humming goes away when I am using both pickups in P90 mode or both pickups in single coil mode.

I was wondering why the hum goes away when I use both pickups in P90 or single coil mode. Does this setting essentially turn the two single coil or P90 pickups into one giant humbucker?

It's not a problem, obviously, just been curious about this.

Ken

p.s. Here's the diagram / pics:

https://forum.seymourduncan.com/album.php?albumid=611

 

[DavidRavenMoon]

Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both?

Humbuckers buck (cancel) hum. Single coils don’t, so they hum.

So the P-Rails will hum in single coil mode. When you have both on in single coil mode they hum cancel.

You always need two operating coils with reverse electrical polarity to cancel hum.


Sent from my iPhone using Tapatalk

 

[Jack_TriPpEr]

Re: Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both

I did a project a couple years ago, installing two P-Rails in an old neck-thru guitar. After starting to install triple-shot rings and deciding I hated them, I decided instead to add four push-pull pots, under the tone & volume knobs, which let me set each P-Rail in any of the four settings (single coil, P90, series humbucker or parallel humbucker). The guitar also has a 3-way switch to move between bridge, neck or both pickups (basic Les Paul type of controls).

There is no humming in either humbucker mode. There is noticeable humming in P90 or single coil mode if I'm using only one pickup (bridge or neck). However, the humming goes away when I am using both pickups in P90 mode or both pickups in single coil mode.

I was wondering why the hum goes away when I use both pickups in P90 or single coil mode. Does this setting essentially turn the two single coil or P90 pickups into one giant humbucker?

It's not a problem, obviously, just been curious about this.

Ken

p.s. Here's the diagram / pics:

https://forum.seymourduncan.com/album.php?albumid=611

The P90 and the Rail coils of the PRail pickup, are just like any other individual coil from a humbucker type pickup when used by itself: each coil suffers 60 cycle hum to some degree. As you reported, the noise does go away when two of the coils are combined. That is the essence of a humbucker pickup, i.e. a second coil is introduced to cancel the hum that you get from just using just a single coil.

 

[ItsaBass]

Re: Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both

Based on what you have described, they must be wired for hum canceling when combined. I.e. one pickup has its coils RW/RP from the other pickup.

Being one who doesn't ever use two pickups at once, I never actually experienced this myself with my P-Rails. But its a sensible way to have designed the pickups, considering that most guitars with single coils utilize the RW/RP technique these days.

 

[Blille]

Re: Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both

What the others said.

To learn more about prails, check this: https://www.seymourduncan.com/blog/the-tone-garage/the-p-rails-wiring-bible-part-1

The article includes the table with the polarity where you can see that the P90s are designed to cancel each other and so are the rails.

Sent from my iPhone using Tapatalk Pro

 

[austin112]

Re: Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both

Thanks for Sharing a great information. I Love to share and resolve the problem.

 

[GuitarDoc]

Re: Why do my two P-Rails hum in P-90 or single coil setting EXCEPT if I'm using both

Congrats on two great pups.

(I happen to love the Triple Shots WAY more than trying to use multiple p/p pots). Good luck with that setup.