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Asymmetrical Coils

Cream Fan

Active member
Joined
May 1, 2003
Messages
2,695
Here's a question for all you PAF fanatics. Which, in your experience sounds better: PAFs with hotter slug coils or hotter screw coils? Is there any consensus on this?
 

In The Light

New member
Joined
Mar 31, 2005
Messages
609
As a foundational concept regarding this topic, with all other variables being equal, the stud side has slightly more output than the adjustable pole side on a traditional humbucker. There is direct contact to the magnet on the stud side, while the adjustable pole side is in indirect contact with the magnet and, additionally, extends out the pickup bottom. There is a slight loss of magnetic field and energy out the bottom of the pickup on the adjustable coil side.
 
Last edited:

JohnH

Member
Joined
May 6, 2007
Messages
363
As foundational concept regarding this topic, with all other variables being equal, the stud side of the coil has slightly more output than the adjustable side on a traditional humbucker. There is a direct connection to the magnet inside the pickup on the stud side, while the adjustable pole extends out the bottom of the pickup. And, there is a slight loss of magnetic field and energy out the bottom of the pickup.

Learnt something today, thanks! i really like the coil cut sound on a neck Hb, and I usually try to arrange things so that it cuts to the adjustable coil, thinking that being the one that pokes its nose out of the casing rather than being covered by it. I might try the other, I could run a test using aligator clips to short one coil or the other...

John
 

jwalker

Les Paul Forum Sponsor
Joined
Dec 10, 2004
Messages
2,597
Okay here is the long and potentially boring techie answer. First off there are no hard and fast rules with PAF's. They vary quite a bit but the coil offset comes pretty close to a hard and fast rule with PAF's. PAF's tend to have a hotter slug bobbin. I am speculating now but I suspect it was intentional. The thinking might have gone something like this, since the screw coil has adjustable poles the output can be tweaked up for that coil by adjusting the screws up so therefore if you make the slug coil just a little hotter you get a wider range of adjustment possibilities because there is a limit to how far down you can adjust the screws and you can adjust the slug coil in any way other than moving the entire pickup. I know this sounds convoluted but think about it.

So how would Gibson have done offset in favor of the slug coil? Of the two machines that I know were used to wind PAF's the first, the Leesona 102 did in fact have auto stop counters. Auto stop counters were standard on the Leesona 102. I used to be of the opinion that the counters probably broke down easily since my Leesona 102 had 2 of the 3 counters dead when I got it. But after talking to a place that makes repair parts for the counters I now believe the counters were apparently fairly durable. In any event when the counters were working it would be an easy matter to intentionally add a specific number of turns to the slug bobbins for a specific coil offset.

The second machine that wound slug coils I own. It does not have an auto stop counter. It does however run at a very slow RPM and has a very reliable mechanical counter and is easily stopped on a dime if monitored. One interesting detail with this machine is that it has a much higher traverse pitch than the Leesona 102. Due to this higher pitch there is just a little more wire going on the bobbin with this machine for each turn than with the Leesona 102. By the time you get to 5000 turns this difference adds up to a pretty "typical" coil offset in favor of the slug bobbin for the same number of turns on both machines. Was this coil pitch difference between machines by design? Could be, I suspect it was built into the machine for the purpose of giving a hotter slug coil. Either way though the effect is the same, a hotter slug coil for the same number of turns.

But still what would account for further variation in coil offset if it was intentional to make the slug coil hotter? Well there is one other detail that accounts for the variation in coil offset that I'm keeping to myself. But that detail explains further variability.

There is one other detail that effects coil strength as it relates to the magnets. The magnet on a virgin PAF tends to be butted against the screw coil keeper bar leaving a slight gap between the magnet and the slug. Why is this? PAF magnets varied widely in thickness. Since the screw coil threads into the base plate on a PAF you need to have the magnet in place under the screw coil when the pole screws are driven into the screw coil. If you don't the pole screws will have to be backed out of the baseplate when install a magnet over .125" and many PAF magnets are over .125". This makes for very inefficient assembly. The easy fix is to just place the magnet under the screw bobbin to act as it's own spacer before the pole screws are driven in. When you do this you just naturally butt the magnet against the keeper bar which makes a gap between the slug coil and the magnet once it is installed. This gap was probably not by design but just a by product of the manufacturing routine. So now you have a detail with the magnet that works against the coil offset in favor of the slug coil. This is one of many small details within a PAF that alone may not seem large but cumulatively add up to a more complex tone.

Personally I prefer the sound of hotter slug coil in the range of what I have seen in real PAF's. Some prefer a hotter screw coil which also sounds good. It' one of my details that can be used as a tonal tweak.
 

Spencer Mumford

New member
Joined
Jun 5, 2004
Messages
260
Intersting tories from Jon. He may be right but I've never seen any discernable pattern on real PAFs.
I think maybe people are looking for things that just were not designed into PAFs.
 

ScottJam

New member
Joined
May 8, 2022
Messages
1
Okay here is the long and potentially boring techie answer. First off there are no hard and fast rules with PAF's. They vary quite a bit but the coil offset comes pretty close to a hard and fast rule with PAF's. PAF's tend to have a hotter slug bobbin. I am speculating now but I suspect it was intentional. The thinking might have gone something like this, since the screw coil has adjustable poles the output can be tweaked up for that coil by adjusting the screws up so therefore if you make the slug coil just a little hotter you get a wider range of adjustment possibilities because there is a limit to how far down you can adjust the screws and you can adjust the slug coil in any way other than moving the entire pickup. I know this sounds convoluted but think about it.

So how would Gibson have done offset in favor of the slug coil? Of the two machines that I know were used to wind PAF's the first, the Leesona 102 did in fact have auto stop counters. Auto stop counters were standard on the Leesona 102. I used to be of the opinion that the counters probably broke down easily since my Leesona 102 had 2 of the 3 counters dead when I got it. But after talking to a place that makes repair parts for the counters I now believe the counters were apparently fairly durable. In any event when the counters were working it would be an easy matter to intentionally add a specific number of turns to the slug bobbins for a specific coil offset.

The second machine that wound slug coils I own. It does not have an auto stop counter. It does however run at a very slow RPM and has a very reliable mechanical counter and is easily stopped on a dime if monitored. One interesting detail with this machine is that it has a much higher traverse pitch than the Leesona 102. Due to this higher pitch there is just a little more wire going on the bobbin with this machine for each turn than with the Leesona 102. By the time you get to 5000 turns this difference adds up to a pretty "typical" coil offset in favor of the slug bobbin for the same number of turns on both machines. Was this coil pitch difference between machines by design? Could be, I suspect it was built into the machine for the purpose of giving a hotter slug coil. Either way though the effect is the same, a hotter slug coil for the same number of turns.

But still what would account for further variation in coil offset if it was intentional to make the slug coil hotter? Well there is one other detail that accounts for the variation in coil offset that I'm keeping to myself. But that detail explains further variability.

There is one other detail that effects coil strength as it relates to the magnets. The magnet on a virgin PAF tends to be butted against the screw coil keeper bar leaving a slight gap between the magnet and the slug. Why is this? PAF magnets varied widely in thickness. Since the screw coil threads into the base plate on a PAF you need to have the magnet in place under the screw coil when the pole screws are driven into the screw coil. If you don't the pole screws will have to be backed out of the baseplate when install a magnet over .125" and many PAF magnets are over .125". This makes for very inefficient assembly. The easy fix is to just place the magnet under the screw bobbin to act as it's own spacer before the pole screws are driven in. When you do this you just naturally butt the magnet against the keeper bar which makes a gap between the slug coil and the magnet once it is installed. This gap was probably not by design but just a by product of the manufacturing routine. So now you have a detail with the magnet that works against the coil offset in favor of the slug coil. This is one of many small details within a PAF that alone may not seem large but cumulatively add up to a more complex tone.

Personally I prefer the sound of hotter slug coil in the range of what I have seen in real PAF's. Some prefer a hotter screw coil which also sounds good. It' one of my details that can be used as a tonal tweak.
I have been trying to nail down a good offset number for making my own PAF replicas. I measured a set from another manufacturer that I really love and was surprised especially at the neck pickup offset. I have read people on forums say never go over 300 turns offset. Well this Neck pickup has .56K offset which is over 700 turns offset. Slug Coil 3.93K Screw Coil 3.37K. Where as the bridge pickup has a lot less offset of only .22K close to 280 turns offset. Slug Coil 4.20K Screw Coil 3.98K. Jon is the .56K offset in my neck pickup considered extreme in your opinion? Have you seen this much offset in vintage PAF's? What is a good average offset in turns or resistance?
 

jwalker

Les Paul Forum Sponsor
Joined
Dec 10, 2004
Messages
2,597
I have seen offsets as high as .56k but it is not common. Judge with your ears. If it sounds good to you then go with it.
 

Johnny Bom Bonny

New member
Joined
Feb 26, 2020
Messages
17
Anyone measuring pickup coils ought to keep in mind that a DC resistance measurement (measured in ohms) does not tell you the number of turns in a coil. Wire thickness can vary, even within a specific AWG number.

According to one experienced pickup winder, PAF wire could vary in resistance from 1.63 ohms per foot to 1.92 ohms per foot. This means that a higher resistance coil could actually have less turns than a lower resistance coil, if the higher resistance coil was wound with thinner wire.

Someone winding pickups in the present day can select different batches of wire, having slightly different thicknesses, for winding particular coils in a pickup. Splicing in a narrower gauge for part of the coil can also be done.

My observation has been that the slightly thinner wire gives less bass and more upper midrange, with also a slight reduction in the uppermost treble harmonics.

To answer the original question from many years ago, in my experience I have preferred neck humbuckers to have more turns on the screw coil, and bridge pickups to have more turns on the slug coil. This keeps the neck pickup sounding clear, and the bridge pickup from sounding sharp.

My own opinion is that coil offset, in number of turns, is often overdone in PAF replicas. I have found that more than around 70-80 turns offset can cause a loss of the typical humbucker quality, and that around 50-70 turns offset is usually ideal. Pickups with matching coil turn counts, but differing wire thicknesses can sound good as well.
 

Wilko

All Access/Backstage Pass
Joined
Mar 11, 2002
Messages
21,046
I've never tried to measure separate coils. How is this done without effing up the pickup?
 

ReWind James

Active member
Joined
Mar 11, 2009
Messages
643
I've never tried to measure separate coils. How is this done without effing up the pickup?
At minimum, you'd have to remove the cover and get a meter probe on the contact under the tape where the two coils connect.

...but what's the point of knowing the DCR of the two coils? I won't tell you anything meaningful. Just that one is either wound with a different coil pattern that takes more wire to achieve, one is wound with thinner average copper core size wire, or one is wound with a few more turns than the other, or some combination of the three. You won't know which of those three are contributors.

If it's a modern pickup and you're just curious and want to know for kicks, proceed cautiously. If it's a vintage PAF, I'd advise against poking around, personally.

Really, your ears will tell you far more meaningful things about the pickup than the DCR of each coil could.
 
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