P90 Tele phase switch query

[stratman323]

I'm thinking of fitting a phase switch on a pull-pull tone pot to this:



But which pickup do I wire to the phase switch? I think I read somewhere that you shouldn't use the bridge pickup, though I'm not clear why, but I only have the braid & the black wire from the P90 so I'm not sure if it's a problem if I use that.

Any suggestions? And has anyone tried phase switching with this combination of pickups? I like it on my 2 P90 LP, & I think it might work on this, for a T-Bone Walker sort of tone.

Mike

[stratman323]

Nobody?

[TeleDrifter]

I've switched both the neck & the bridge, works either way.......

[stratman323]

So it doesn't matter if the outer braid from the P90 becomes the hot output when the switch is pulled?

[stratman323]

No other replies? Come on guys, I need some help here!

[jlerhun]

Originally Posted by stratman323

So it doesn't matter if the outer braid from the P90 becomes the hot output when the switch is pulled?

It should not matter, as long as the braid is not touching ground (cavity shielding) or almost ground (the player, which acts like an antenna). As the P90 is enclosed in plastic, the latter is less likely.

If it happens to be noisy, you can leave the neck pickup alone, and switch the phase of the bridge pickup instead.
Just make sure that there is no connection between the baseplate and the "cold" wire, but still a good connection from the baseplate to ground (either through screws and bridgeplate, or with a dedicated wire).

[stratman323]

So I would need to run an extra ground wire from either the neck or the bridge pickup? I'm not sure I'm confident to do that myself.

Maybe this is all more trouble than it's worth?

[BenM]

If you have two stock pickups or after market pickups with only two wires you will not be able to just reverse the polarity. If you go this route, when you touch the pole pieces of the pickup you switched it will buzz because you will be touching the hot side of the circuit, kind of like when you touch the tip a 1/4 jack when the other end is plugged into your amp. This is made more complicated by the fact that you will lose shielding, and by the fact that the ground of the bridge pickup is most likely making contact with the bridge. You might be able to just disconnect the wire between the metal base plate and the lead, but you have to be careful.

[TimTam]

Do you know how many wires you've got coming from the bridge cavity ? Should be easy to determine just by taking off the control plate. If it's just two, they 'MAY' be both ungrounded from the bridge pup. If so, your job is easy. You'll just flip the two with your phase switch.

However, to find out if one's actually a ground, and if you don't want to open the bridge cavity to see where each wire comes from, you can check with a multimeter to see if either wire has continuity (0 ohms) with the bridge or the poles .... in which case it's a ground.

If there's only two wires and one is a ground, then you'll need to get in and unground the current ground at the pup end, and add a new ground (possibly just a wire slipped between the bridge and the body).

If you've got three wires, one WILL be a ground - which could be connected to the bridge (check with the multimeter), or could also be to a pup base plate like in jlerhun's linked pic. The ground wire of this 3 should be obvious as it will go to the back of a pot on the control plate. Leave the ground alone and flip the other two wires for your phase swap.

Bottom line is you need two ungrounded wires from one pup to flip its phase.

If the P90 has only the bare shield plus a hot wire, I'd leave that alone. Work with the bridge pup. Anyway, open up the control cavity and see what you're playing with.

[stratman323]

Originally Posted by TimTam

Do you know how many wires you've got coming from the bridge cavity ?

If you've got three wires, one WILL be a ground - which could be connected to the bridge (check with the multimeter), or could also be to a pup base plate like in jlerhun's linked pic. The ground wire of this 3 should be obvious as it will go to the back of a pot on the control plate. Leave the ground alone and flip the other two wires for your phase swap.

Bottom line is you need two ungrounded wires from one pup to flip its phase.

.

Three. A black & a white from the bridge pickup (an SD Broadcaster), & a black that runs from under the bridge to ground on the back of the volume pot.

(Incidentally, there's no wire from the back of the volume pot to the back of the tone - presumably the metal control plate makes the earth connection here?)

So, because of the extra earth wire from under the bridge plate, does this mean that I can just connect both black & white wires from the bridge pickup to the push/pull pot to reverse the phase?

[TimTam]

Originally Posted by stratman323

Three. A black & a white from the bridge pickup (an SD Broadcaster), & a black that runs from under the bridge to ground on the back of the volume pot.

Ah ... the fact that you've got an SD in the bridge means that even though you already have 3 wires coming from the bridge cavity, you should cut any connection from the base plate to one side of the pup, that hard-wires that side of the pup to ground ...
http://www.seymourduncan.com/support...ele_lead_phase

Originally Posted by stratman323

So, because of the extra earth wire from under the bridge plate, does this mean that I can just connect both black & white wires from the bridge pickup to the push/pull pot to reverse the phase?

Basically, yes. Like this ...
http://www.seymourduncan.com/support...al_singlecoils

Hope you end up with a cool new sound !

[stratman323]

Originally Posted by TimTam

Ah ... the fact that you've got an SD in the bridge means that even though you already have 3 wires coming from the bridge cavity, you should cut any connection from the base plate to one side of the pup, that hard-wires that side of the pup to ground ...
http://www.seymourduncan.com/support...ele_lead_phase



Basically, yes. Like this ...
http://www.seymourduncan.com/support...al_singlecoils

Hope you end up with a cool new sound !

Sorry, maybe I'm stupid, but I don't understand what you mean by "you should cut any connection from the base plate to one side of the pup". And why does it make a difference if the bridge pickup is an SD?

[TimTam]

Originally Posted by stratman323

Sorry, maybe I'm stupid, but I don't understand what you mean by "you should cut any connection from the base plate to one side of the pup". And why does it make a difference if the bridge pickup is an SD?

The simple answer is because Seymour Duncan says so in the link I provided ... and he knows how his pups are wired ...
http://www.seymourduncan.com/support...ele_lead_phase

The wire in the diagram ties one side of the pup permanently to what would usually always be ground. To flip the phase you flip what would usually be the pup's ground wire and its hot wire (ie the hot becomes the ground). You can't do that if one side is permanently tied to ground ... at least not without risking the side effect BenM described earlier.

The significance of it being an SD is that they are one of the group of Tele bridge pups that can have the metal base plate (and ground connection).
http://www.seymourduncan.com/product...ntage_broadca/

I haven't dealt with a lot of different Tele bridge pickups, but my 1980s Fender bridge pickup for example doesn't have the metal base plate.

[stratman323]

I still don't really understand I'm afraid. Surely the defining factor in a Tele bridge pickup is that it has a steel base plate?

If it means cutting a wire on the pickup, I'll have to leave it. I'm not fiddling with one of my favourite Tele bridge pickups. I assumed it could be done without the need for this. If it can't, I won't bother with the phase switch.

[TimTam]

Baseplates on single coils are not mandatory, but apparently more complex than they look ...
http://www.tdpri.com/resourceBASEPLATE.htm

If you don't want to take the chance that cutting the link would change your sound (I don't know enough to tell you if that is at all likely), then after cutting the link you'd have to run a new wire from the baseplate to ground in the control cavity. Then your guitar would be electrically identical to now.

But you said you didn't want to do that.

However if the pup screws contact the baseplate and the bridge, which is independently grounded, then the link is actually redundant, since the baseplate is then grounded via the bridge. So you can cut the link and the baseplate should still be grounded. You can check with a multimeter. So again your guitar will be electrically identical to now.

Bottom line is that you can't flip the phase if one wire from the pup's coil is grounded to the base plate.

[caytele]

...i'm assuming your tele has a 3 way switch...if you are not going to proceed with the "phase switch operation"...then here is another way to get another cool sound from that guitar; if you have a good quality switch like a CTS or as provided on the fender USA (with the "see through" design) etc, you can carefully position the switch lever IN BETWEEN (turn up the volume on your guitar and amp, and you will be able to hear when it JUST engages the other pickup) the position for the neck and the position for the middle (combining bridge and neck)..gives you a slightly different, (but way cool sounding to my ears) "neck/bridge) sound...If the switch is a good quality one (firm/stiff) it will stay in this "in between" position, even though it is not a "proper" stop/position...try it and see if you hear any difference between it and the formal "middle" position....

[thrashmetl]

I'm not going to be technically helpful here, but I recently had a P-90 installed in the neck of my Tele. When I got it back it was out of phase. The neck was wired 3-conductor so all I had to do was switch two of the wires and it put the two back in phase, but I did have some fun with it before I did so and it sounded pretty awesome. Even though it was two single coils, you could kind of het that Peter Green sound, it was great for blues. I would definitely recommend doing the phase switch if you can figure it out.

[cc9cii]

Put the phase switch on your neck pickup. Treat the shield as the negative lead.

[jlerhun]

Originally Posted by stratman323

(Incidentally, there's no wire from the back of the volume pot to the back of the tone - presumably the metal control plate makes the earth connection here?)

Yes, this relies on the not-very-reliable contact with the control plate. Better to have a wire. Don't fear "ground loops", there won't be any there.

Originally Posted by stratman323

So, because of the extra earth wire from under the bridge plate, does this mean that I can just connect both black & white wires from the bridge pickup to the push/pull pot to reverse the phase?

In your case, no.
It's not because of the earth wire under the plate (which is good), but because the SD pickups has a redundant link between negative (aka "cold" lead) and the baseplate of the pickup. Which is itself connected to the bridge with mounting screws, therefore grounded. Cutting the redundant connection, as explained by SD, will change nothing in your sound.


To sum it up :

1. Try to swap the leads of the P90. It's unlikely to be noisy. If you like the OOP sound, wire a switch and you're done.
2. If that happens to be buzzing anyway (e.g. you can't avoid touching the polepieces), you still can have the phase feature with the other pickup
3. Put back the neck pickup connections as they are now
4. Remove the bridge, and cut the small wire link under the pickup as pictured on SD website.
5. Wire the leads from the bridge pickup to the phase switch. It works exactly like in step 1).

In any case, pickups that were hum-cancelling in the midde position (parallel in-phase, with one pickup RWRP) will become hum-helping in out-of-phase wiring.

[stratman323]

OK, now sorted. I used the P90 & there are no problems with it that I can tell, at least at home volume. It's a cool sound, I like it, it's not that far away from an LP with 2 P90s out of phase.

So thanks to everybody for your help. Such helpful people on this forum.