Help shielding p90s

[zionstrat]

Folks-
Going with SD p90-1s on my current project and getting ready to shield- I'm phase reversing and these are 2 conductor which leads to a couple of questions-

1. Stewmac kit suggests unhooking wires from the coil, wrapping with copper strip and then attach new ground wire to copper- Is this really necessary? Could I shield the pup cavity instead? I've never taken apart a good pup and it scares me silly-

2. They also say that this mod is necessary to phase reverse and I'm definately phase reversing- If this is truely a problem with an p90-1 I'm assuming it's because as a 2 conductor, the negitive is grounded to the base plate and when inverted the noise of the base plate would now be on the positive side?

Anyone who has had to deal with this and can give me more direction would be highly, highly appreciated!
Cheers

 

[Evan Skopp]

Re: Help shielding p90s

Reversing the phase is something you only do if the two pickups are out of phase relative to each other. It's won't create a hum-canceling effect. You need reverse magnetic polariy and reverse winding direction.

Don't unhook your pickup leads. You'll void your warranty on the pickup. To do a thorough job of shielding your guitar, you'll need to shield the pickup cavities as well as the insides of the pickup covers. And make sure everything is grounded.

 

[Zhangliqun]

Re: Help shielding p90s

Evan's right -- there is no hum-cancelling with a true single coil pickup like the P90. That only happens when you have two coils that are RWRP relative to each other, either via your traditional side-by-side humbucker or a stack. Reversing the leads will just put your P90 out of phase with any other pickups on the guitar, unless you also flip the magnets, and then you'd be right back where you started from anyway.

That said, proper shielding can help a lot.

 

[zionstrat]

Re: Help shielding p90s

Thanks for the replies guys, but let's take it to the next level as there are a couple of different issues and I dont think I explained it correctly-

1. This will be a rwrp set- The purpose of phase reversal in this case has nothing to do with noise reduction- I simply am going to have out of phase/in series as one of the pup selections.

2. I'm trying to stick to non-noise canceling p90s because I love the real p90 sound, but this will be a stage guitar and I have had big problems with p90 noise in the past. I already shield the cavity, I'm looking for more pup shielding.

3. So stewmac has instructions that allow 2 things:
A. Shielding around the coil
B. Adding a separate ground so that the 2 wires can be inverted for out of phase.

With all of this restated, here's the stewmac instructions (under single coil) and now I hope my first post makes more sense?
Thanks in advance!


http://www.stewmac.com/shop/Electron...9.html#details

 

[MikeS]

Re: Help shielding p90s

These are questions I had last night when trying to diagram the schematic for my SG project.

Are traditional dual P90 guitars loaded with a rwrp pickup for hum canceling in the middle position?

Zionstrat inspired me to try this with my SG: two DPDT switches. One is a phase reversal for the bridge pickup, and the other is a series switch (both only work in the middle position of the toggle switch). Whether or not I would use them all, the scheme would leave me with four possible combinations at the middle position:

1 – Parallel, in phase
2 – Parallel, out of phase
3 – Series, in phase
4 – Series, out of phase

The wiring I have figured out. What is throwing me for a loop is whether one pickup has to be rwrp for this to work. I don’t necessarily need hum canceling in any position. The pickups are Hot P90(b) and Vintage P90. Until I get home I can’t tell you if I had the foresight to order a rwrp at the neck or not. I know the phase switch only puts the pickups electronically out of phase, so I’m obviously concerned about how the polarities of the two magnets work with or against each other in this wiring scheme.

How does one deal with the braided ground of a single conductor pickup for this kind of wiring? Is it as simple as insulating the braid and soldering a new lead to the braid?

I’m not trying to hijack a thread, zionstrat, I’m hoping maybe we have some of the same questions.

 

[zionstrat]

Re: Help shielding p90s

Mike, glad you're trying the series/out of phase thing as well, but hoping I haven't lead you down too dificult a path- I know there must be a resoultion as I know others who have used this sound on p90s and I've done it with strat and tele pups myself-

But considering the input I've had so far, Stewmac seems to be correct and this will be harder for a 2 conductor P90- Here's what I think I understand..

1. Yep, stick to RWRP for the traditional 2pup noise canceling
2. If the negitive lead is not carying a lot of shielding that will insert noise into the positive side when phase swithced, I may try to shield the pup cavity and just switch the 2 leads as standard- But I think the neitive is carying the baseplate ground.

But, if it turns out that I have to add the 3rd lead and actually shield the coil as Stew mac suggests, I'm not sure I want to go that direction- First of all Evan reminded me that it will kill the warantee- But if it isn't that hard a mod (and it doesn't sound like it) maybe I will try anyway- But I certainly need some input from someone who's done this first or has more expereince as I don't take apart good pups very often

Here's another direction to consider- I intentionally routed the body deep so that I can try the stacked p90s if worse come to worse- Considering that it doesn't show, I would have even routed this myself, and if we dont get a better solution on the p90-1 this is certainly a direction to consider. I've never heard the stacked p90, but I think most agree that it sounds different enough from the classic p90 to be an issue.

But I'm sure hoping to get a better understanding on this shielding issue as I stupidly sold my sg special years ago because it just couldn't handle stage RF and don't want to just repeat that problem.

Well, now that there are two of us searching, maybe we will get an answer twice as fast
Cheers

 

[zionstrat]

Re: Help shielding p90s

BTW, Mike, I love the experimenting you are up too and cant wait to hear the results-I haven't tried all of the combos you are looking at, but I've heard the p90 series in phase and thougth it was just way too much 'raunch' to be of any use- But that's the point of exepmenting eh? might turn out to be something that works great with your rig/style-

Just wanted a disclaimer as I know you saw this in my current design, but I have very, very low expectations for this combo-

 

[MikeS]

Re: Help shielding p90s

Hehe, I didn't embark on a P90 SG project for it to sound like an angel. I've got enough guitars that sound nice an smooth. AFAIC, with this project, the raunchier the better. Worse case scenario is that I don't like the tones and don't end up using them. BUT, the possibility will always be on tap.

I'm going to try and fugure out how different polarities affect this scheme. The electronic phase isn't a concern as this will be switchable, but I have a feeling that a reverse polarity neck would have much different results than a neck pickup with the same polarity as the bridge pickup. I'm not sure if this would be for the better or for the worse.

Pardon if this is a answered somewhere else, but are Seymour Duncan P90 neck pickups already RWRP in relation to the bridge P90s? The main page doesn't list RWRP as an option for P90s.

 

[Scott Miller]

Re: Help shielding p90s

Okay---everybody out of the pool!!

Seriously, though. here is what you do. No shielding of the coil will be necessary. If you look on the bottom of your Duncan P-90, you will see that there are two wires coming from the coil. One of them is connected to the inner black cloth wire of the single-conductor cable. The other wire is connected to the outer braided portion of the single-conductor cable.

SO---disconnect the wire from the OUTER BRAIDED portion of the 1-C cable. Attach another piece of wire to it, and now you are free to use that wire (along with the black cloth wire) as you two leads for the phase switch. Then, make sure you ground the braided wire because that will be grounding the bottom plate, pole pieces, etc. That should do it.

 

[MikeS]

Re: Help shielding p90s

Awsome, thanks Scott!

 

[zionstrat]

Re: Help shielding p90s

Scott- You're the man! Thanks big time-

Mike,ain't this fun? Can't wait to hear how it works-

m

 

[MikeS]

Re: Help shielding p90s

This is a lot of fun. Worst thing about it is the wait… I’m doing a nitro finish and have only gotten the grain filler applied and sanded. Still a ways out from finishing the SG.

I may try the mod on my HWY1. I’m thinking a phase mod, series mod, and a switch so that the bridge pup is always on tap. I think I’m going crazy.

 

[Zhangliqun]

Re: Help shielding p90s

1. This will be a rwrp set- The purpose of phase reversal in this case has nothing to do with noise reduction- I simply am going to have out of phase/in series as one of the pup selections.

Gotcha.

2. I'm trying to stick to non-noise canceling p90s because I love the real p90 sound, but this will be a stage guitar and I have had big problems with p90 noise in the past. I already shield the cavity, I'm looking for more pup shielding.

The real P90 sound is best -- and so far hasn't been duplicated. I bet Kinman is working on something though...

3. So stewmac has instructions that allow 2 things:
A. Shielding around the coil
B. Adding a separate ground so that the 2 wires can be inverted for out of phase.

I see. Yes, you do need a separate ground lead to ensure that the shielding and plate, etc., are grounded at all times, whether you have the pickup in phase or out. Otherwise, when you throw the switch, you'll get all the noise back and a lot more because the shielding in the pickup cover, the baseplate, and the braiding on the outside of the lead will be acting as noise ANTENNAS, rather than shunting the noise to ground.

As far as making the phase switching work in general, it doesn't matter if the two pickups are RWRP relative to each other. Either way you still wouldn't have as much hum-cancelling in one of the two phase positions. The only question is whether you would get the hum-cancelling in the in-phase position or in the out-of-phase position.

 

[MikeS]

Re: Help shielding p90s

Zhangliqun, but for hum cancelling, wouldn't the polarities have to be opposite. The phase switch only flips the electronic phase if I'm understanding this right. Therefore, a RWRP would in fact be noise cancelling in one of the positions. If there was no RWRP pickup you'd never have a true hum cancelling position.

Do I understand that right or do I need to consult an electronics for dummies book?

 

[zionstrat]

Re: Help shielding p90s

Think I've got this correct- 2 variables effect noise cancelling in rwrp-
1. magnetic orientation
2. coil wind direction = reversing leads

So by definition, with rwrp set, shouldnt an out of phase single coil be non-noise defeating beause the leads are reversed?
Ie, this is why I want to really shield the pup or the cavity when it's our of phase-

But maybe I'm missing something-
cheers
m

 

[Evan Skopp]

Re: Help shielding p90s

2. coil wind direction = reversing leads

Reversing the leads doesn't reverse the winding direction.

 

[Zhangliqun]

Re: Help shielding p90s

Zhangliqun, but for hum cancelling, wouldn't the polarities have to be opposite. The phase switch only flips the electronic phase if I'm understanding this right. Therefore, a RWRP would in fact be noise cancelling in one of the positions. If there was no RWRP pickup you'd never have a true hum cancelling position.

Do I understand that right or do I need to consult an electronics for dummies book?

I think you're right -- and I'm starting to get a headache...

 

[Zhangliqun]

Re: Help shielding p90s

Reversing the leads doesn't reverse the winding direction.

No, but it does reverse the current.

 

[zionstrat]

Re: Help shielding p90s

No, but it does reverse the current.

bingo- i thought this was equivilent?

Ie, when you wind your humbuckers, don't you have 2 choices on the coils?
1. truly wind them opposite directions
or
2. wind them the same direction but reverse the leads