Old 03-25-2018, 03:24 PM   #1
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Default Wiring 2 P90s - questions about phase (and more...)

Too lazy to join a guitar forum, hoping someone here can help.

I have couple P90s: a Seymour Duncan 3N-J P90, and a "Genuine Gibson USA Single Coil P90 ST Bridge Pickup" that the seller said he believed was in a Melody Maker. The latter has 4+ground, which makes me suspicious it's a humbucker, but whatever.

As I understand it, if you have independent volume controls, you can turn one pickup down a bit, and get pretty usable sounds out of the Out of Phase tone. Building on that, is it possible to wire some sort of capacitors in the 2 and 4 positions that would "automatically" cut a bit of the signal so that the bridge would be stronger in 2, and the neck stronger in 4? What kind of cap would be appropriate?

Last edited by Reason; 04-24-2018 at 08:13 AM.
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Old 03-26-2018, 09:57 AM   #2
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Your post raises a number of questions. You mention 2 and 4, which must be switch positions, which leads me to believe you're using a 5-way switch. Is there a third pickup? Is it a "standard" strat-style 5-way? Are you intending for the pickup selections to be otherwise normal (N, N+M, M, M+B, B) parallel strat wiring?


Edit -
Assuming the answers are all Yes, I'm afraid my answer to your question is No. There's no good way to make that happen. In short, anything you do to one pickup will either affect that pickup in every position where it's active or affect both active pickups at the same time or both. To keep it all passive, and maintain what you've got for tone otherwise, is pretty much impossible.

If you wanted to go active and change to a Superswitch, we might be able to make something happen.

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Old 03-26-2018, 12:34 PM   #3
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OK, thanks very much for your input. I guess I'm spoiled by Reaper's routing abilities and was hoping I could add a Send to the cap and then adjust the return levels.

A superswitch is not out of the question, as I'll be replacing the current electronics anyway. Active pickups ARE out of the question as I want to use what I have - is that what you meant or is there another meaning to "active" here?

If not then I'll probably just go with individual tone and volume pots for each pickup, and either a three way toggle or individual on/off switches. Or maybe a regular 3 way switch just to keep the standard strat-ish look.

I had edited my post a couple times before hitting submit and ended up losing info, so details are below.

The reason the whole phase thing came up was because I had read somewhere that SD and Gibson use default configs of P90s that could cause Out of Phase issues when the two brands are used together.

Yes, this is for a strat-style guitar. Specifically an Ibanez Gio GRX40* that was picked up for $25.

I'm not able to get anything interesting out of the stock pickups. I'd bought the P90s separately, intending to replace the P90s in another cheapo I got, but was able to get usable tones out of those by adjusting pickup heights, so scrapped the replacement idea.

I thought it might be fun to have a P90 strat, and for the price of entry, figured why not. If I can get the intonation correct, I might even slap on the bottom portion of a 7 string set and go baritone, but that's separate.

*Side note that is less relevant to my question: guitar is bathtub routed, so the P90s will physically fit. However I plan to get some pickguard material and make my own custom pickguard.

So after all that - can you clarify what you meant by active? Any other thoughts/comments/suggestions welcome, of course.
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Old 03-26-2018, 03:31 PM   #4
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IF you were willing to put a buffer between each pickup and the switch, you might be able to use one pole of the switch to do something or other, but I'm not sure it's worth the trouble to design, test, install, and maintain such a thing. I personally hate the idea trying to keep a battery inside a guitar.

Independent V and/or T really gives you a lot more options and can stay passive. This would require up to six pots on a three pickup guitar, but you could maybe use stacked pots or something.

Then you have to decide if you want "normal" or "backwards" V wiring. With normal, turning one pickup all the way down kills the whole guitar in an position where that pickup would be on. Backwards avoids that, but can change the feel of the taper a little, and will leave the output jack floating in the EM wind (potentially buzzing/noisy) when you turn it all the way down trying to get silence. I generally think that if you're choosing a combination of two pickups, it doesn't make sense to turn either one all the way down, and that it can be cool to deliberately turn one all the way down and then use the pickup switch as a kill switch, so I'd prefer it wired normal.

Then you have to decide on "modern" or "50s" wiring for the Ts. The difference is actually which lug of the V pot that the T pot is connected to and how the Vs interact with the Ts but also how the individual Ts affect each other.

But first you need to figure out what's happening with the pickups and their relative phase. It's easy enough to get the string-sensing phase of any two pickups to match - just swap the wires on one until they're in phase. But if you also want them to be noise-cancelling in combination, it can take a bit more doing. There are easy ways to test the pickups and figure out which goes which way, then you can look at what it will take.

Now, if you wanted to add an actual phase switch or two, there are ways to wire those with caps to get what some people call "half out of phase". I'm not actually convinced that's interesting enough to bother either, but it's an option for you to consider.
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Old 03-27-2018, 12:08 PM   #5
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OK, cool. It's going to be just the two P90s. I do have an old EMG Select SC, but when I googled it, other people who have done similar things found that the SC was overpowered by the P90s, didn't add enough tonal variety, and physically impeded strumming/picking.

I wasn't aware of the backwards volume wiring option, but I agree with your assessment when it comes to usability. IMO, volume all the way down = no sound from the guitar, and I like the pickup selector "killswitch" effect, and if I want only one pickup, that's what the selector is for.

I do think the independent tone and volume wiring will be worth futzing with. I have some knobs I can play with to check placement, and some mini pots should let me fit all 4 in there.

Thanks for all your input, it's really helped me clarify where I want to go with this.
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Old 03-27-2018, 12:43 PM   #6
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Oh well if there's only two pickups, things are simplified a bit. Do you want them to be OoP by default?

My suggestion would be to replace the 5-way with a one of those 4-way "Baja Tele" switches so you can have the series option. Then I'd just do master volume and individual tones wired directly across each pickup. Maybe one of those pots is a push/pull phase switch. Then you can have in or out of phase in series or parallel. My experience has been that SOoP > POoP in most every case. The individual Ts will actually be both basically master T in parallel modes, but in series, they can create a sort of half out of phase thing as well as what we call "broadbucker" which is like the girth of the full series pair with the top end of a single. May not be exactly what you thought you wanted, but it'll give you a bunch of useful tones you may have never thought of.
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Old 04-02-2018, 11:35 AM   #7
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Good question. I haven't played with OoP tones, so I don't know if I'd find them useful. I did wire my 7string with push/pulls to switch the humbuckers to series/parallel, and those are interesting sounds, but not the same thing.

I expect to sell the stock pickguard as a prewired unit, so I'll be replacing all the electronics. I'll have to figure out if I want to get a superswitch or a 4 way for half the price.

Also kicking around putting in some slide pots instead of round pots, but the smallest I've seen are 45mm long (with a 30mm throw) so not sure they'd actually save me any space.

maybe I'll actually get to play this frankenstein in 2018, ooh, there's a goal!
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Old 04-23-2018, 08:42 PM   #8
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Alright I think I'm going to forgo phase switching in my, uh, switching plan. I'm going to try and cram 4 pots into the space of 3, or maybe crowd into the space normally reserved for the 5-way.

I'm thinking a couple of toggle switches might be nice, and I think an on/off/on would let me add a direct-to-jack bypass on each pickup. So I'd have

controls engaged
killswitch
controls bypassed.

I have to admit I've never fully understood SPDT/DPDT enough to know how it applies to this plan, though - anyone know if which I'll need?
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Old 04-23-2018, 10:19 PM   #9
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Definitely needs DPDT. One side switches the top of the pickup between the top of the V pot and the tip of the jack. The other connects the jack top to the V wiper or the top of the pickup. The T pot will be wired directly across the corresponding V and will just get switched "for free". You still get to pick which "side" of the V pot it goes on - that "modern" vs "50s" thing...

Realize that the "killswitch" position actually just leaves the wire from the jack top hanging in the wind. That won't be worth mentioning until you turn off all the pickups hoping for silence. I've described normal volume wiring which will cause silence when one one is both active and turned all the way down no matter how many other pickups are on and turned up. so when you're going to set it down and walk away, leave at least one pickup on (controls engaged) and turn it down. If you want to play the switch for that stutter thing, turn one all the way down and engage it when you want to mute.
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Old 04-24-2018, 09:39 AM   #10
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Really appreciate all the help.

Can you elaborate on the electrical implications of "hanging in the wind?" sounds like simply turning both pickups "off" via the switch won't result in silence if the volume on either (or both?) is up. Is that / could that be a problem? Is there a wiring fix, or would I need a different type of switch?
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Old 04-24-2018, 10:24 AM   #11
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When you turn the switch off, the pots are disconnected from the output, so they can't help you either way. With both switches off, the jack is left open, which is actually slightly worse than just unplugging the cable and leaving it to buzz away on the floor. You shouldn't be able to hear the strings from the pickups anymore, though you actually might in some cases since the pickups ARE still attacked to the circuit at one end, but it will be very susceptible to any EM/RFI noise in the environment.

When you want real silence, you need to short the jack - tip to sleeve. "Normal" wired V pots do that when they're turned all the way down, but not when the switch has taken them out of circuit. With a center-off switch like you'll be using, there's really nothing to be done about that. You don't want those switches to short the jack anyway, because they'd both be master kill switches and you'd never be able to have just one pickup unless maybe if you do the "backwards" V pot wiring, but I don't think it's a huge issue. When you want actual silence, turn one of the V pots down and leave that pickup on with controls engaged.
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