Addressing Z Coil issues

I began a new Topic to make it easier for interested parties to have access to information regarding Z Coils and the S-500/Legacy/Comanche body route.

Body Route - 3 5/8" wide, 5 5/8" long
Body Route clearance to end of neck 9/32"
Body Route clearance to vibrato screws 3/16"

Z Coil
Magnet type - hard ceramic
Magnet size - 1 1/8" X 1/2"
Coil flatwork - 5/8" X 1 1/2"

Coil Shim Size
1 1/4" X 5/8" X 1/8"
3 holes of 3/16" width have to be drilled to allow the threaded coil pole piece inserts to be in contact with the magnet

Pole piece design

1) The threaded pole piece inner piece can't be threaded out the bottom of the stationary part. The stationary part has a 1/8" area machined in it to accomodate the end of the inner pole piece section which is larger than it's threads. At the bottom of the stationary part is another 1/8" area the same as the top. The stationary part was made the same top and bottom.

2) I couldn't find a matching thread for the inner threaded part of the pole pieces, but the ID of the threads on the stationary part is slightly larger than 1/8".

3) I couldn't thread the inner part of the pole piece into the stationary part from the bottom of the coil even after cleaning out all of the excess glue. Running a 1/8" wooden dowel through the stationary piece is a great way to clean all of the glue out the bottom (after popping the coil off the magnet).

4) The coils are held in place by the magnet primarily and somewhat by the glue.

I learned all of this attempting to elevate the coils above the magnets with the idea that I'd run the inner pole pieces out the bottom of the stationary parts, which the design won't allow likely to keep us from adjusting the inner pieces out the bottom and pushing the pickup apart. To elevate the coils I have to extend the pole pieces as there has to be magnetic continuity from the magnet through the pole pieces. To do this I have to use something ferrous with an outer diameter of 1/8". Metal round rods are available, as are a variety of fasteners. My current pick are 6 penny common nails, the expanded nail head will add stability to the pickup - that and a little glue/wax should let me elevate the coils to reduce the magnetic force and increase the induced signals in the coil.

I also tried to find a reference to provide the magnetic strength at the pole piece of a Z Coil relative to other types of pickups, there's not many sources but I did find one that measured Z Coil magnetic strength at 1100 gauss, which is the same as current production 57/62 Strat pickups from Fender (from the tdpri website). Numerous sources from G&L indicate that Leo was looking for a specific magnetic strength at the pole pieces of MFDs pickups, but they don't state what the level is. These measurements are taken in contact with the pole pieces. String level readings are much lower (20s to 30s).

wgusa has a chart with several readings, Gibson P90s and humbuckers are in the 200 to 400 gauss range.

The reason I needed to know was if G&L pickups had gauss readings similar to P90s and humbuckers then where was my string pull and wolf tones coming from? It all made sense when I found the one reference that stated that a MFD pickup had measured in the 1100 range. Granted that was for a jumbo MFD bridge pickup, but all MFDs are covered by the same patent and all were variations on the design of a ceramic 5 magnet and pole pieces with various coil configurations. It makes sense to me that Leo would target a similar gauss level as his single coil pickup designs. If this assumption is wrong I'd really like to know what that gauss level target was.

My next task is cutting those 6 penny common nails and checking the stability and alignment of my proposed modified Z Coil design. If acceptable I'll modify the neck and center and check my Will Ray bridge to see what can be done there as the Will Ray coil is already taller than the standard Z Coil configuration.

More work coming. And I still need to post my audio file of the wolf tones I recorded with my neck and center pickups bottomed out and the Will Ray with roughly twice the pickup to string clearance than is recommended by the G&L set up manual.

Cheers.

FWIW, the article in Vintage Guitar magazine, "Out-Stratting the Strat," by a couple of G&L experts, gives these stats for the S-500 type MFD pickup:
"Measuring the Magnetic Field Design Pickup
• DC-R = 4.2-4.7K
• Inductance at 1 KHz = 2.6H
• Resonant Peak = 7.0 – 7.6KHz
• Output = 200mV
• Gauss (at top of poles) = 300-420."

https://www.vintageguitar.com/20843/out-stratting-the-strat/

tomanche
Thanks for the reference and info. I read the article in the link and found that the S-500 pickup being measured had a comparable gauss level similar to a Fender Strat. Rather than focus on the numbers I'll accept that the relative gauss meters aren't calibrated to provide an absolute measurement but are repeatable enough to provide relative readings so that a similar gauss reading of a S-500 MFD and a Strat pickup is a trustable measurement.

Which takes me back to my initial reasoning that Leo used a large ceramic magnet that 1) provides a similar magnetic gauss level as a Strat on top of the pole pieces and 2) spreads that magnetic field to a much much larger string length than the small pole piece magnets in a Strat pickup. Which gets me back to the string wolf tones with my Z coil pickups set to a height much lower than that specified by G&L and only as high as the pickguard to eliminate those wolf tones.

I've slowed down on my G&L Comanche VI+ project due to yard work here in Bluffton. So it will be awhile before I get back to raising the coils on my Zcoil pickups.

I'd still love to hear from someone who knows what gauss level Leo was shooting for with his MFD pickup design. The article you linked makes that statement but doesn't state what that target level was.

Additional Z Coil details

The bar magnets are 1/4" in height.

The coil height of a standard Z Coil is 1/2" from the bottom of the flat work to the top of the stationary part of the pole pieces.

The coil height of a Will Ray Z Coil is 9/16" from the bottom of the flat work to the top of the stationary part of the pole pieces.

Note the same cover is used for both Z Coil pickups, on the Will Ray the cover doesn't touch the baseplate (by about 1/8") which puts all of the spring pressure on the cover dog ears. I don't like that design.

My thought to raise the coils by adding additional length (6d nails sized to 1/8") would also put all of the spring pressure on the cover dog ears. That plus my dissatisfaction with the bar magnet/pole piece design resulting in a huge magnetic field at the strings has led me to a different solution.

I noted in a prior post that a 1/8" dowel will fit through the stationary part of the pole piece (with the inner adjustable portion removed). My solution now is to remove the bar magnets from the base plate, purchase 1/8" diameter/5/8" length rod magnets, then shim the coils to properly fit the pickup covers (1/4" for a standard Z Coil, 3/16" for the Will Ray). The total length of coil and shim height above the base plate has to be 3/4" for the pickup cover to seat onto the baseplate.

I've chosen neodyium magnets with a Br of 13,200 gauss which compares favorably to AlNiCo 5 at 12,500 gauss (which would be a modern day Strat magnet choice). Keep in mind that these are .125" magnets vs the .195" magnets installed in Fender Strats/Teles. The resulting magnetic field at the string will be more focused than a standard Strat/Tele but at the same intensity within the .125" diameter, the stationary portion of the pole pieces will also come into play with a lower gauss level than a standard Strat/Tele in the annulus between the .125" and .195" diameter.

I will install all the magnets across the pickup as either N or S, no splitting of the N/S polarity for each of the three strings as is currently done. The magnet polarity doesn't affect the humbucking aspect of the pickup windings. The N/S polarity of the current Z Coil magnets (and their excessive magnetic energy) does create out of phase tones for those strings not above that pickup half that when combined with the other pickup half are objectionable to me. And lastly the huge bar magnets made it impossible for me to avoid wolf tones even with 2/3 of the pickups adjusted down to the pickguard level and the treble pickup less than halfway up (and below the G&L recommended pickup height), these wolf tones were even present on open strings (a situation I never encountered with Strat pickups). So the bar magnets are getting the boot.

I haven't decided whether to proceed with the coil shielding idea. The copper tape and insulating tape are here and ready to go but I'd rather not use that for fear of losing precious treble due to parasitic capacitance. I also have to decide on what to do with my limited tone control, I do have the tiny capacitors used in the bass rolloff circuit and will have to use a fixed resistance vs the variable resistance the unmodified guitars have. I figure a setting of 3/4 or 1/2 of that 1 Meg ohm resistance would be about right.

I can't predict what the outcome will be of these modifications. The neodyium magnet has approximately the same gauss as AlNiCo 5 magnets on modern Fender pickups, but the field will be focused to a smaller area than a Fender. Available literature discusses the Fender narrow aperature magnetic field of the single coil pickups as being low of bass, high on midrange, and not reaching very high into the available treble range of the string and harmonics and my aperature will effectively be smaller than that. But I'm dissatisfied enough with the current Z Coil magnetic design to throw in the towel on it and try this in an attempt to make a usable pickup. These modifications will result in a pickup that's more similar to Seth Lovers patent from the 50's than G&L's patent for MFD pickups. I may end up with nothing for the $200 I spent on these pickups and I'm willing to accept that risk as they are not usable as originally built.

I understand that there will be different opinions on the Z Coils. If you run lots of distortion and gain it might be a perfect pickup fpr you. I don't and I hear the defects badly enough for me not to want to play the guitar even without an amp (wolf tones are still present on the entire neck).

I'll take some photos as the mod progresses and I'll post the results good or bad.

I've completed converting 1 Will Ray Z Coil and 1 standard Z Coil from the ceramic (5 per the literature) bar magnet to 6 individual pole magnets located within the stationary part of the pole piece in the pickup. I've checked the magnet polarity and all are the same for both pickups on all six magnets, the coils have continuity, and I wired one pickup up temporarily to an amp and held it above the strummed strings of my Stratocaster and it works.

I did have some thoughts on the impact of the remaining stationary parts of the pole pieces with these 6 individual neodyium 42 magnets. Initially I wanted to keep the magnet tops flush with the top of those pole pieces mostly for appearences. Later I realized that would be a mistake.

What does a pole piece do? Essentially a pole piece is a ferro resonant material that is a magnetic short circuit (in the real world it's a lower "impedance" magnetic pathway) for the magnetic lines of force. For my project the pole piece is surrounding the magnet and the magnet is slightly longer than the cylinderical pole piece. When I put my neodyium magnets into those cylinderical pole pieces the magnet would self center with either the top or bottom of the magnet flush with the pole piece and the other ending with the magnet hanging out. That fits with the how I envision how the magnetic lines of flux would emanate from this magnet/pole piece design. The magnet end outside of the pole piece has much more magnetic flux airborne than the other flush end (which has most of the magnetic flux in the pole piece). Realizing this aspect I set the magnets to extend out of the stationary pole piece below the strings.

I can't find any free software online to model my magnet/pole piece design (and I don't have a flux/gauss meter) but one can generalize several things and that may be good enough for this design:
1) The magnetic flux above the pickup will be in a much smaller volume than that of a bare magnet.
2) The magnetic flux returning to the opposite pole of the magnet away from the string will be almost entirely within the stationary pole piece. Meaning less impact to the adjacent string and it's magnet/pole piece compared to other designs.
3) The magnetic flux at each string is less with the magnet/pole piece than that of a bare magnet. Meaning I'll have to raise the pickup closer to the string for a given pickup output signal. String pull should (hopefully) also be reduced reducing wolf tones.
4) Due to the stationary pole pieces the baseplate will have less of an impact on the pickup's magnetic field than a standard Z Coil. In the original Z Coil the baseplate spreads the magnetic flux out and impacts the inductance of the pickup. In addition the pole magnet/pole piece design results in the baseplate having a lower impact on the pickups inductance.
5) The magnetic flux of my pickup will interact with less string length than a bare magnet design (i.e. a standard Fender single coil) and less than a standard Z Coil design.

To summarize for my pickup I anticipate less magnet flux (gauss) at the string, a smaller volume of string impacted by the pickups magnetic field, less magnetic field impact to adjacent strings and their magnetic circuit than other pickup designs, along with lower inductance in the pickup due to reduced baseplate impact on the pickup.

The next step is to complete the modifications on the remaining pickup, modify my tone circuit from treble cut to bass cut, and remount the pickups and pickguard assembly back into the guitar.

For info the magnets I selected are from K&J Magnetics model D2A. In hindsight I should have ordered D2A magnets for the standard Z Coil modification and D2C magnets for the Will Ray as this would give me 1/8" of magnet above the stationary pole pieces, currently I have about 1/16" of magnet above the pole pieces for the Will Ray pickup. That might be enough. A D2A is 1/8" diameter by 5/8" long, the D2C is 1/8" diameter and 3/4" long.

Good picking!

I put some pictures of the conversion of my Z Coils from ceramic bar magnets to pole piece magnets inside the stationary part of the original pole pieces in my Gallery. Take a look. I also put some future ideas and time savers along with the photos.

I did some checks and note that the base plates are no longer magnetic as it was in the original design. This is consistent with my thoughts on the impact of putting magnets inside of the stationary pole pieces, the baseplate is no longer a significant contributor to the magnetic flux pattern in my design and likely will no longer have a significant impact on the inductance. Additionally the finished pickups no longer stick together due to the magnetized baseplates.

In the original MFD design the baseplate sets the shape of the magnetic field. Basically the magnetic lines of flux return to the ceramic magnets glued below the coils via the edges of the baseplate. The baseplate is significantly magnetized, if you remove the pickups from your guitar they will magnetically attach themselves to each other quite strongly. In my design each string's magnetic field is set by the diameter of the pole piece and magnet which is roughly .2". In the original MFD design magnetic flux moves across the pickup (due to the opposite polarity magnets) set by the dimensions of the baseplate which is 5/8" along the string and 3 3/8" across the strings. In the original design magnetic flux moves from any pole piece to any other polepiece within the same pickup, in my design there is little (if any) magnetic flux from one magnet/pole piece assembly to another magnet/pole piece assembly within the same pickup.

I still need to reassemble the guitar and give these a try. I'm leaving my tone control circuit unchanged for the time being, I need to hear these before I modify that. I anticipate sounding very much like a standard Strat/Tele with little (if any) crosstalk between the two halves of the pickup.

I put the guitar back together last night. The magnets above the pole pieces aren't going to work out due to the string to body clearance on this guitar. Also these magnets are too strong with bad wolf tones on the treble strings, oddly there were no wolf tones on the bass strings. The bass strings sounded nice and snappy with lots of treble.

The next step is to reevaluate the magnet length and perhaps diameter and make the magnets flush with the top of the pole pieces. This time rather than using surface flux I'll calculate the magnetic strength at 3/32". Searching the internet there's little information for magnet strength at string height (minus the actual string as that perturbs the measurement). I did find a reference from an individual with a calibrated flux meter whose measurements were slightly above 100 at 3/32" above the pole pieces of a Gibson humbucker and 400 at the same height above a Strat pickup.

My original magnet selection was based on the calculated contact flux which was 13,200 gauss vs the same value for an AlNiCo magnet of the same size of 12,800. Lesson learned there's more to what a magnet does in a pickup that calculated contact flux. The part I missed is to use the calculators to determine the string height flux - which is dependent on the magnet material or the Brmax, the diameter, and the height above the midpoint of the magnet (which would include the string height). Of course the magnet is assumed to be fully charged, I know there are ways to demagnetize a magnet but it's hard to predict what the outcome will be.

The D2A from K&J Magnetics is not a good choice for a replacement magnet unless you've shimmed the neck and bridge to raise the strings further away from the body of the guitar. My guitar has 6/16" of clearance string to body, my Strat has 7/16".

Last edited by Rodney Hamblen on Sun May 22, 2022 11:06 am, edited 1 time in total.

https://music-electronics-forum.com/for ... kup-theory

You really should post some questions in this forum. There are a ton of really knowledgeable pickup makers who will respond and help you troubleshoot your technical issues. There are also other forum members who have an encyclopedic knowledge of the theory.

jdetente
Thanks for the idea but I don't anticipate finding much help.

I'm constrained to use a 1/8" diameter magnet rod, the only ones available (not custom ordered) are made of ALNICO 5 and Neodyium N42 and N52. N42 and ALNICO 5 have essentially the same magnetic flux (within 3%), N52 has more magnetic flux which I don't need.

Where I made my error was by extending the magnets 1/8" above the coils. I got significant wolf tones. After spending some time with K&J Magnetics flux calculator I now understand what is needed when selecting a magnet.

The magnet selection HAS to be based on the available height adjustment range of the pickup on the guitar. Assuming you can lower your pickups flush into the pickguard the available range is the string height above the pickguard. On my G&L that's 6/16", on my 1973 Strat that's 7/16". I've seen a wide range of string heights above the body for Strats through the years, but I've never seen a Strat that if you adjusted the pickups all the way up that the pickups wouldn't be in contact with the strings.

So looking at the G&L Owners manual they recommend 1/32" clearance for the high E string height above the pickup polepiece and 1/16" for the low E string. These numbers relate back to the magnetic strength selected for the pickups. For N42 (essentially the same strength as ALNICO 5) I calculate a magnetic flux of 1940 gauss for a 1/8" x 5/8" magnet (this is a smaller diameter than the .187" or .195" magnets normally found in a Fender single coil pickup) at 1/16" clearance. At 1/32" clearance we have 3753 gauss. That's high enough to cause wolf tones but it's not a spot on the guitar we normally play and the high pitch of the note may hide any wolf tones.

To pick the correct magnet you have to have the string height above the body for the range on the neck that you'll play in and then select a magnet to give you 100 (typical Seth Lover humbucker) to 400 gauss (typical Fender single coil) at that height.

Here's a table of gauss readings for N42 magnets, 1/8" diameter and in various lengths.

Height above magnet 5/8" .2" 1/16" 1/32" Magnet length

1/16" 1940.5 1768.9 1238.3 825.9

1/8" 694.1 586.5 358.7 236.5

3/16" 330.2 256.7 141.9 87.9

1/4" 186.8 134 73.9 40.7

5/16" 117.8 82.4 40.3 22

(Note that the 5/8" Magnet length column is representative (3% higher flux here) of current Strat/Tele pickups, again this is for a 1/8" diameter pickup vs. .187 or .195")

Here are surface contact flux readings for ALNICO 5, N42 and N52 (1/8" x 5/8" magnet):

ALNICO 5 12800 gauss
N42 13200 gauss
N52 14800 gauss

Time to conclude something. My guitar has 6/16" of string height above the guitar body and it plays well at that level. The string adjusters don't appear to have much upward adjustment left but it is possible to shim the neck and bridge (I don't use the whammy) to raise everything up 1/8" or so. I'd rather not have the shims. I see now why I've ended up with my Strat and Tele pickups low and close to the body, in that 3/16" to 1/4" clearance range to get away from wolf tones on those guitars. I'm liking the 1/16" and 1/32" magnet lengths (and that would be regardless of using N42 or ALNICO 5). Lots of adjustment range.

Concerns - If you have or have read about gauss level at some elevation above the magnet please share that with me, or even better if you have actual measurements.

When the Fender single coil pickups were designed it was all cut and try as there weren't any computers and this is a tough calculation to perform by hand. My opinion today is that our beloved Fender Strats and Teles magnet design was based on how tall the coil had to be to hold all the wire and not on a gauss level. It just happened to work out that for the myriad of string to body heights for these guitars and the different ALNICO magnet materials (and magnet charges) available at the time of construction that one could adjust the guitar and pickups and find a setting that sounded good most of the time.

Pickup and guitar design and adjustment have a lot of variables, the old cut and try method still appears to be the best approach to get a decent tone.

Still in pursuit of the sound.

If you're a pickup designer or builder I'd like to hear from you regarding how you select the magnets for your pickups especially if you're doing something unique.

I think they would be able to help with some of the theoretical issues in your assumptions and perhaps lead you on the a path to correct the perceived issues with the pickup. I went back and played a partscaster that I put together with z coils and what I found is that if I use the normal amp settings that I have for other guitars, there is too much bass. I use the bass cut on the guitar and adjust the amp settings to remove some bass and the issue goes away. Doing so gives me a sound much closer to a typical strat...but your mileage may vary.

Edit: Also, I can't recall if you checked...but was the pickup microphonic at any point. If the ceramic magnets and base plate were ever loose that would cause the pickup to become microphonic and could cause the sounds you are describing as wolftones.

jdetente

No problem with loose parts on my Z Coils causing wolf tones. I agree that if your magnet is moving at all the coil will see that as signal and amplify it. I had wolf tones even when played acoustically.

I've done a lot of reading and performed a lot of calculations on magnet sizing and how that relates to pickup height adjustment. Its been an educational experience.

When I selected my initial 1/8" X 5/8" neodyium N42 magnets I fell into the old trap of emulating past designs. I couldn't change the diameter but I picked the length as a representative length for a Strat magnet. I could have moved those flush with the tops of the stationary pole pieces and would have fully emulated a split Strat single coil, wolf tones and all. A neodyium N42 is only 3% stronger magnetically than AlNiCo 5, they are essentially the same magnetic strength if sizes are the same.

I used K&J Magnetics online calculator to determine magnetic flux at levels starting at 1/16" above the magnet to 5/16" above the magnet in increments of 1/32". Bottom line the magnets don't have to be as long as is per common practice (roughly 1/2 to 5/8"), a much smaller magnet at the top of the coil will provide adequate flux - not full AlNiCo 5 magnetic flux at the same elevation above the magnet but certainly within the adjustment range. For example you like AlNiCo 5 at 3/32" above the magnet , a 1/8" X 1/16" neodyium magnet at slightly further than 1/6" above the magnet will give you the exact same magnetic flux (including the impact of slightly raising the coil toward the string) - it is within the range of adjustment of the smaller magnet (somewhere between 3/32" and 1/16").

I have ordered 3 different magnets at about $1.50 for 10. I ordered enough to use the same magnets for all 18 positions (3 Z Coils), or I can use different magnets for each pickup (weaker for the neck, stronger for the center, strongest for the bridge). Or an idea I like better is to use the strongest magnets under the 2 lowest strings, the next stronger magnet for the two middle strings, and the weakest magnets for the 2 highest strings on all three pickups. Not having to magnetize a magnet while putting the coil form together gives me a lot of flexibility. Having the stationary pole pieces provide the mechanical stability for the pickup gives one a lot of flexibility to mix magnet strengths in a pickup, and magnetic field size.

One surprising result from the multiple calculations was the realization of what a short vs. long magnet provide in terms of a magnetic field. A longer magnet just extends the vertical size of the magnetic field. Since we don't care what the magnetic field looks like extending into the body of our guitar below the coil we can shorten the magnet substantially and get rid of it. For a 1/8" X 1/16 magnet the magnetic field is pretty much gone at 5/16" above and below the center line of the magnet. A 1/8" X 5/8" magnet the magnetic field is pretty much gone at roughly 1/2" above and below the magnet - for most of the string to magnet spacings we encounter the shorter magnet provides enough magnetic flux and the coil is closer to the string as well which supports the patent goal for MFD pickups to allow the use of less windings leading to less noise.

I'll see how this all works out. I've learned a lot so far.

I ended up installing 1/8" x 1/8" Neodyium 42 magnets in all three Z Coils on my Commanche 6+ in all string positions. I installed all the magnets with the same polarity (opposite polarity poles aren't needed for humbucking). The results are outstanding.

I first adjusted the pickups fairly high to check for wolf tones and I did still have them, then I lowered the pickups until the wolf tones went away.

Results:
1) Chimey and glassy like a Strat but with splitable coils on each pickup. The out of phase (two or more pickups together) sounds are wonderful with quack everywhere you'd expect to have it on s properly set up Strat. Tele tones on the Bridge/Neck coil pairs. It's interesting to get the EAD strings quacking but play a single coil on the GBE strings, each chord you play only the bass strings quacking and the treble strings coming through straight.
2) Even with these small magnets I still get a bit of cross talk across the pickup (low strings inducing signal in the treble coils), but everything is now in phase due to all the magnets being the same polarity across the Z Coil and pickup to pickup, and the amount of the cross talk signal is greatly reduced. I did not install any copper shielding tape for this iteration.
3) The guitar volume seems unchanged with these smaller magnets. Indicating that once we start getting wolf tones we're not adding a lot of magnetizing force to the strings. Using larger (stronger) magnets just increases wolf tone and cross talk problems, you don't get any more signal out of the pickup and you'll end up with the coil at a lower height to get rid of the wolf tones. However, reducing magnet size to the point that wolf tones are present at the tallest height of these pickups that you'd be comfortable playing on would get the coils closer to the strings and that should increase the volume.

Thoughts
1) Its a lot of work but for me it's worth it. Redesigning these Z Coils to reduce the excess magnetism put me in no mans land from a theoretical standpoint. There's no data that I could find that says how much magnetic flux is too much. There are few available design calculators for determining the expected flux at a given height for a given magnet (fortunately K&J Magnetics has one for rod magnets). There is a lot of flux measurement data on the internet but I question whether these are useful as absolute measurements and feel that these are better relative measurements. I could find no data that answered the question how much magnetic flux will give wolf tones nor what the maximum magnetizing force is for a given string.

Now that I have a known configuration and known magnetic strength I can back calculate the flux level that causes wolf tones. I'll vary the height of one pickup until I get the tones, measure the string to magnet distance, and back calculate the flux. This will be an approximation as the magnetic flux picture is a lot more complicated from this pickup with 6 magnets vs a single magnet but that's the best I can do. From my searches there's not an existing value on the internet that identifies this flux level - so at least we'll have a starting point.

2) Even 1/8" x 1/8" is too large of a magnet. I got wolf tones on the GBE strings at a lower pickup height than I was hoping for. At the level the GBE strings had wolf tones the EAD strings did not. I also have 3/32" and 1/16" magnets that I've yet to try. I'm going to play this guitar for a while and retire it as a test mule for the time being, it's as close as I've ever had to my dream instrument. But improvements are still out there. My view of a perfect pickup would be one with varying magnetic strengths for each of the strings commensurate with the level of flux that causes wolf tones. I don't want to tilt the coil away from the GBE strings because the magnet is too strong which is what I have today. I want the coil level flat or tilting up towards the GBE strings.

The classic way of staggering magnets to balance string volumes from a pickup makes little sense to me, varying the coil design/height is a better alternative. Another approach would be to get 2 Will Ray coils and install those under the GBE strings of the neck and center pickups. I still like a full Will Ray pickup in the Bridge position - that pickup is located in an area where string vibrations are limited due to the bridge position close by. So if I undertake another Comanche 6+ build I'll start with 2 Will Ray and 1 standard Z Coil.

3) My theory on Z Coil humbucking and N and S magnet polarity for the two coils of a Z Coil is correct, the humbucking aspect comes from the RWRP coil assembly and has nothing to do with the magnets. One magnet polarity across the pickups will ensure that any cross pickup signals aren't objectionable.

4) Z Coils with properly sized magnets can be coil split to provide many great sounds and combined in ways that Comanches were never built to provide.

In Summary
I pursued this project with the same cut and try method that gave us the renowned pickups of the 50s. This method results in good sounding pickups (when properly adjusted) but gave us little understanding of why. I've got a much better idea of the design aspects after pursuing this project. Here's a partial list of the necessary information that help select a magnet strength:

1) Available range of string height adjustment above the guitar body
2) Available pickup height adjustment relative to the guitar body
3) String saturation point for magnetization (no available data)
4) String magnetic flux where wolf tones are created (no available data)
5) Minimum pickup clearance guitar string to pickup top
6) Magnet type - single magnet per string, bar magnet
7) Magnet field manipulation - pole pieces, magnet materials guiding returning magnetic lines of force to the opposite magnet pole
8) Economic factors (a single bar magnet is cheaper than 6 individual string magnets)

With this info we can pick a magnet strength for our pickup, with the missing data flagged above a pickup designer/modifier is in the "cut and try" arena. I suspect that item 3) is ignorable as item 4) occurs at a lower magnetic flux level (we'll prioritize sound above output). I left magnet materials off the list - if we're building pickups in great numbers we change the magnet material to give us a desired magnetic strength when the pickup comes out of the magnetizer. For our purposes we're modifying a bar magnet pickup to a magnet per string design controlling the magnetic output by specifying the length of the magnets.

I'll try to develop some info on 4) with my guitar and share it here.

The Z Coil is a unique pickup that provides excellent results by modifying the magnetic design. Perhaps due to string height adjustment limitations my Z Coils were unusable at any elevation due to wolf tones with the standard bar magnet design. I modified these pickups replacing the bar magnet with a non magnetic shim, removed the threaded pole pieces and put some 3/8" set screws into the void left by the pole pieces to assist in magnet alignment, and installed a singled 1/8" x 1/8" Neodyium 42 magnet per string on each pickup. For the GBE strings the 1/8" x 1/8" magnet is still too large. More work remains but I'm going to play this guitar for a while as I'm very pleased with the sound as modified. There's still room to optimize these pickups on the GBE strings. The pickups perform well with split coil switching and many sounds are now available that a standard Comanche doesn't have.

I've posted some as finished photos in my gallery of the current Comanche 6+.

Hi Rodney, this is fascinating, thanks for posting in such detail!
How difficult were the z-coils to disassemble?
I'm embarking on a project of my own and looking to mod the pickups, so any tips or advice would be greatly appreciated

Patricks
Great question. In order here's what I did with my Z Coils. I'll be doing a similar project with 6 S-500 pickups in a S-500 using a Chandler 6204 pickguard as I did before. I'll load each pickup with 3 bass or 3 treble magnets after removing the ceramic magnet. 6 on/off switches, I'm skipping the phase in/out option for this build but I am keeping the Stereo/Mono switch.

In order after removing the Z Coil pickups from the pickguard and wiring:

1) Remove the plastic covers. On 1 pickup there was excess glue on the cover which ripped up some of the windings on one of the two coils. I unwrapped the broken wires and resoldered it restoring the pickup with a slightly less resistance. Some have luck with a heat gun, I'd shoot for at least 200 degrees to liquify that excess glue (I didn't have a heat gun). It appears that the magnet to the baseplate and the coil to magnet are all glued and aligned in one step before the glue hardens using the pickup height adjustment screw holes as the alignment reference points - any excess glue that squeezes out of the coil to magnet connection ends up on the pickup cover below the coil wiring which creates the coil breaking hazard as you lift that pickup cover off.

1a) Cut the ground lead between the treble coil low side connection and the baseplate. You can get to this ground lead from the middle of the coils.

2) Carefully pry the coil from the magnet, you can use a piece of wood or whatever seems handy. It's possible to damage the coil wiring doing this so it's best to do your prying on the end of the coil without wiring coming out from the pickup, perpendicular to the pickup. The glue between the coil and magnet prys loose very easily.

3) If you're getting rid of the ceramic magnets (which I highly recommend) try cutting the glue bond between the magnet and baseplate all around the magnet before prying with a screwdriver. Or you can brute force the magnet with a grip wrench (don't do this if you will reuse that magnet for something later). If you're going with an individual magnet per string use a 1/8" diameter neodyium magnet, I found 1/8" length was a little too much magnet still. Note that N42 magnets have almost the exact same strength as AlNiCo 5 for a given size.

4) If you're pitching that ceramic bar magnet you'll need 1/4" shim material to keep the pickup baseplate/coil/missing bar magnet in the proper config for the pickup cover you'll reuse.

5) When you're putting it all back together scrap off any excess glue from the inside of your plastic pickup covers so as not to break windings again when you reassemble the unit. You can pre glue your 1/4" shims to the baseplate using the magnet's footprint on the baseplate, but when gluing the coils to the shims put the cover on at the same time and use the cover and your pickup elevator screws threaded into the baseplate to keep everything properly aligned while the glue dries.

So it's not too bad as far as disassembly but I'll say when I initially ripped those coils up removing that pickup cover my heart sank. Fixing a broken coil winding took about 2 hours working carefully to fix it.

I haven't pulled my S-500 pickups apart yet but they will definitely be different. The baseplate for a S-500 does not have the elevator screws in it, these are part of the plastic cover. So it appears I can heat up the partial baseplate and pry it off and hopefully remove the bar magnet without removing the coil from the pickup cover. We'll see.

Ask me again if I missed something.

Wonderful, thanks Rodney!
I'd heard about the fine wire breaking when the pickup cover comes off, I can't imagine the feeling when the wires tore. Luckily mine came away cleanly the last time I had it out of the guitar so fingers crossed it'll stay intact when I start to mod it.
Fantastic tips about prying away the coil, too. I'll post up with the results of mine
Cheers
Pat

Pat
The first Z Coil I removed the magnet from I was very careful and took a lot of time getting that ceramic bar magnet separated from the baseplate. By the time I got to the last Z Coil I didn't care about the condition of that bar magnet after I'd removed it and it went much faster.

Good luck. Other than directly hitting the coil wires with a lot of force the coils are fairly rugged. I put a layer of glue on my coil wires for extra protection, a thin enough layer that the coil form was wider than the dried glue on top of the coil. Getting the glue off after damaging a coil would be very hard, consider this a long term commitment. Since I was done with the coil wiring I thought that this was a good step to take.

Remember Dr. Frankenstein had to start somewhere before assembling his monster.
Rodney Hamblen