Casbahroc 7/9/2018 4:25 PM
How to build and increase output of P90?
So I wound my first set of P90s using the AllParts P90 kit. I used 42 AWG wire and got 10,000 winds on each. When I set them up they sound good but are much quieter than my other guitars. (I usually play with volume set to 1/4 on my amp but with these I have to crank it up to about 3/4). I used a 500k volume pot, 250k tone pot like I have on previous builds. I have adjusted the height of the pickups and everything but they are still relatively quiet. Any insight on how I could make these things louder would be great. Thanks!
 
big_teee 7/9/2018 5:00 PM
Welcome to the forum.
A P90 uses 2 alnico bar magnets on the bottom of the pickup.
Both bars have to be oniented the same polarity.
Usually N/N, is how they are oriented.
S/S would also work.
With 2 pickups one N/N, and one S/S would give RWRP with both pickups in use.
You don't want them S/N, or N/S.
That would reduce the magnetic gauss, and make a weaker pickup.
I would start by checking to see that the magnets are oriented correctly.
GL,
T
 
big_teee 7/10/2018 11:58 AM
I mainly make Fender style Single Coil pickups, gibson style Humbuckers, and varieties of different bass pickups.
In my lurking around the web, refreshing how to make a P90 Pickup, I ran across these instructions.
They show the magnets, and polarity placement.
https://www.stewmac.com/How-To/Onlin...le_Bobbin.html
https://courses.physics.illinois.edu...eport_Sp10.pdf
The Stewmac guide should be sound.
Didn't overly scrutinize the Dan Carson guide, but the magnet placement looks correct.
Only thing I didn't care for was how they unspool the wire. unspooling off the end is now the accepted way.
The second guide specifies 10,000 turns for the bridge, and 9500 turns for the neck which sounds reasonable.
If you know of better P90 instruction guides, please place them here.
T
 
big_teee 7/10/2018 12:37 PM
Here's some winding data, I came up with a while back, but never tried.
It looks reasonable at 90% bobbin tpl density.
One for the neck, one for the bridge.
It lists A2, A5 magnets, pick one type per pickup, not both.
Give it a try if you want to.
T
 
Steve A. 7/10/2018 11:03 PM
Quote Originally Posted by big_teee View Post
Welcome to the forum.
A P90 uses 2 alnico bar magnets on the bottom of the pickup.
Both bars have to be oniented the same polarity.
Usually N/N, is how they are oriented.
S/S would also work.
With 2 pickups one N/N, and one S/S would give RWRP with both pickups in use.
You don't want them S/N, or N/S.
That would reduce the magnetic gauss, and make a weaker pickup.
I would start by checking to see that the magnets are oriented correctly.
GL,
T
With the like poles facing each other it creates a VERY STRONG magnetic charge of the opposite polarity on the adjustment screws and (optional?) keeper bar. The resulting flux pattern of a P90 is quite different from a strat or PAF pickup. I'll post a picture if I can find one. (As I recall there is one in the Donald Brosnac book on Guitar Electronics but I would need to scan it.)

So what is the word on keeper bars? I know that some winders use 'em and some don't...

When I got a new Gibson LP Jr on clearance about 15 years ago it came with ceramic magnets. I tried every combination of A2, A3, A4 and A5 magnets, mixing & matching them and flipping the pickup around - they all sounded great! - but I went back to the original ceramics as they gave me the widest variety of sounds from the single pickup and two controls.

P90s are amazing animals... on one hand you have the raucous sounds of George Thorogood and Leslie West and on the other you have the mellow jazz guitarists of the 50's... Perfect in every way except for the hum when used alone. Add a modern style dummy coil and you're in Seventh Heaven!

Steve A.
 
Helmholtz 7/11/2018 7:21 AM
The mild steel keeper acts as a pole shoe. It collects the flux from the magnet(s) and provides a low impedance magnetic path to the pole screws. But there is an additional benefit in P90s. Without the keeper each magnet feels more of the other's repelling field. This demagnetizing field may permanently weaken alnico magnets (ceramics do not show this effect). With the keeper the magnets actually see a weak attracting and thus stabilizing field.
 
Steve A. 7/11/2018 12:05 PM
Quote Originally Posted by Helmholtz View Post
The mild steel keeper acts as a pole shoe. It collects the flux from the magnet(s) and provides a low impedance magnetic path to the pole screws. But there is an additional benefit in P90s. Without the keeper each magnet feels more of the other's repelling field. This demagnetizing field may permanently weaken alnico magnets (ceramics do not show this effect). With the keeper the magnets actually see a weak attracting and thus stabilizing field.
Thank you for explaining that! I always thought it was kinda sloppy to skip the keeper & baseplate and just glue the magnets to the bottom of the bobbin...

Steve A.
 
big_teee 7/11/2018 12:09 PM
Like mentioned, the steel keeper also gives more steel surface to stick each magnet to.
Without the steel they want to push away from each other.
The keeper helps the magnets stay put, and gives a nice even field.
Some of the cheap imports don't use two magnets, just one strong ceramic.
They work OK, but I prefer two alinco's, for me two A2s.
T
 
Helmholtz 7/11/2018 1:09 PM
Where's the OP? Problem solved?
 
big_teee 7/11/2018 2:09 PM
If you look at the bottom of thread?
You will see he has not been back since he made the OP.
That was his first and only!
We may not see him again.
Thanks for all the input everyone!
I enjoyed it, whether the OP, got anything from it or not!
T
 
Steve A. 7/11/2018 11:22 PM
Quote Originally Posted by big_teee View Post
If you look at the bottom of thread?
You will see he has not been back since he made the OP.
That was his first and only!
We may not see him again.
Thanks for all the input everyone!
I enjoyed it, whether the OP, got anything from it or not!
T
It's only been a few days... my guess is that he hasn't gotten around to checking the magnets yet. As to whether he will ever return your guess is as good as mine!

Did we tell him that when he puts the magnets together without the keeper bar they should repel each other? I wonder if the P90 kit instructions emphasize that point...

EDIT I don't think that the Allparts kits come with instructions...

https://www.allparts.com/PU-6992-000...it_p_4790.html

https://www.allparts.com/PU-6993-000...it_p_5009.html

Steve A.