LoZ Pickups

[Cashmaro]

I bought a Lace Alumitone Deathbucker and am amazed at the harmonics I get out of it. Otherwise, it appears to be a treble-heavy pickup. I replaced the neck humbucker on my BC Rich Warlock and I get a similar sound to the stock bridge pickup, except it is much easier to excecute artifical harmonics.

I was so intrigued, I decided that I wanted to make one myself as a project and as the Alumitones are quite pricey despite the obviously low cost to produce them.

I did a lot of reasearch, including looking through many of the posts on this site. It looks like Lace boosts the low impedance of the single loop from the aluminum bracket/ceramic magnet by adding a secondary loop (the square shaped bracket off of the primary loop) with tertiary loops, which are two bobbins wrapped with fine copper wire (AWG 43?). The two bobbins also act as a humbucker as they they can be wound out of phase. Am I correct in this?

I was looking at getting a 2.5 inch X 1 inch X .125 thk piece of aluminum C-Channel to make the primary loop, which I can cut to width. I can do the machining with a pattern similar to the Alumitone and weld on feet to the bottom for mounting to the guitar with screws. I have some rectangular Neodymium-Iron-Boron magnets I can use to replace the cermaic magnets. I assume this should give me higher inductance in the primary although the permeability of NIB magnets is the same as cermaic magnets, and from the inductance equations it appears permeability is the limiting factor for inductance. Would the NIB magnets give higher output?

What are my options for assembly from there? I don't want to just rip off the Lace design. I figure I could use a transformer (500:1 maybe) in series with a noise canceling transformer to complete the assembly. My main concern is having approximately the same output amperage/voltage as the Alumitone or other regular humbucker so I can replace the bridge pickup on my guitar.

[big_teee]

Do they sound that much better than a conventional Hi Z type pickup, or are they just unique, and you want to do something different?
I really don't see anything that lacking in regular Humbucker pickups.
I can build all the Harmonics I can stand into a regular Pickup!
T

[Cashmaro]

Do they sound that much better than a conventional Hi Z type pickup, or are they just unique, and you want to do something different?
I really don't see anything that lacking in regular Humbucker pickups.
I can build all the Harmonics I can stand into a regular Pickup!
T

They do sound better, in my opinion. Some people don't like them, or active pick ups for that matter, but they are great for my personal style. I get the same growl on my low end but the highs and harmonics do stand out better. My brother put two on his guitar, and bridge pickup has the standard growl under distortion but screams like a banshee when hitting harmonics. It depends on the listenener. You could theoretically get a similar output by switiching from 8000 turns on conventional windings with 42 or 43 AWG wire to less windings with thicker wire, getting rid of some capacitance. One issue is that more room is needed, since inductance is directly proportional to wire cross section, but number of turns squared is proportional to inductance. Correct me if I am wrong, but capacitance does shift the output curve of the pickup to the left. I couldn't hit an artificial harmonic on my original neck pickup (BC Rich BDSM) when soloing, but i often like to do my solos getting the bluesy sound I get from the neck pickup.

Plus, I think it would be fun to have another project.

[big_teee]

They do sound better, in my opinion. Some people don't like them, or active pick ups for that matter, but they are great for my personal style. I get the same growl on my low end but the highs and harmonics do stand out better. My brother put two on his guitar, and bridge pickup has the standard growl under distortion but screams like a banshee when hitting harmonics. It depends on the listenener. You could theoretically get a similar output by switiching from 8000 turns on conventional windings with 42 or 43 AWG wire to less windings with thicker wire, getting rid of some capacitance. One issue is that more room is needed, since inductance is directly proportional to wire cross section, but number of turns squared is proportional to inductance. Correct me if I am wrong, but capacitance does shift the output curve of the pickup to the left. I couldn't hit an artificial harmonic on my original neck pickup (BC Rich BDSM) when soloing, but i often like to do my solos getting the bluesy sound I get from the neck pickup.

Plus, I think it would be fun to have another project.

Sounds like fun.
BTW welcome to the Forum.
Back to the Low Z pickups.
I made a Strat Neck Pickup with 41 Ga Wire, and it was too bright for me.
The only way I could get the tone I wanted was to shorten the bobbin to fatten up the sound.
That limited the amount of wire I could put on the pickup.
so I went back to my 42 AWG Heavy coated wire.
Good Luck,
T

[Cashmaro]

Tank you T for the warm welcome.

[FunkyKikuchiyo]

I was expecting cute memes, perhaps with kittens, until I realized that it said LoZ instead of LoLZ....

[David Schwab]

There are a couple of threads here on Alumitone type pickups.

Here's a good one:

Low Impedance Pickup Research

[Cashmaro]

There are a couple of threads here on Alumitone type pickups.

Here's a good one:

Low Impedance Pickup Research

David,
I have scoured the threads on this site regarding LoZ pickups. I particularly find BBSailor's comments some of the most helpful, as he seemed very interested as well. I decided to start posting here because the other threads on this site made me believe this was something I could do.

My main question is what all the voodoo is in the shrinktube on the underneath of the alumitone. It looks like no one was willing to sacrifice one and take one apart, but who would a $100 a pop. It looks like 2 bobbins coiled with fine wire. I dont want to rip off his idea but I think understanding the concept helps.

I have the neodymium magnets I would like to use, and I have a chunk of scrap aluminum that I could hog out to make the bracket. I was thinking of making a 1/2 inch thick bracket to double my loop area. Since the Neodymium has a 5X gauss rating, at the distance from the strings I plan to have in my design, as the ceramic magnets, I figure I can get 10X the amount of inductance out of my primary loop. I could then use a small step-up transformer to get the voltage and amperage I need and a second transformer for noise cancellation. Excess voltage could be controlled with a resistor in series. I am not very good with electronics and the Inductance equation becomes kind of confusing with this loop geometry, but I think my assumption is correct.

I plan on using off the shelf transformers that I could hopefully tuck in the cradle of the bracket. I figure if the one I make sounds good, I could come up with a detachable pickup for my bass so I can have a bridge or neck pickup.

[Cashmaro]

David,
I was checking out your store and I see you use Neodymium in some of your pickups. What pull force is acceptable on my strings before funky things start happening? I tried using some online magnet calculatorsand it looks like the magnets I have pull with .11 lbs of force from a 3/8 inch space between the strings and the magnet. Is that too much?

[madzub]

I have taken a couple of Alumitones apart, and rewound the secondary coils with about 300 turns each of 34 awg wire, then use a mic transformer at the amp. I'd have taken photos of the innards but i haven't got a camera. I've ruined a few $100 pickups over the years due to my insatiable need to open things up. But hey, i just rebuild them better!

But yeah, it's just what you think it is, a couple of plastic bobbins through which the c-shaped core laminations fit together, with many wraps of very thin wire on the bobbins, wrapped in tape, then the wire leads and ends of the bobbins and core are potted in epoxy. Actually i think the black shrink wrap is wrapped around first, the the epoxy poured in.

[Mike Sulzer]

I was thinking of making a 1/2 inch thick bracket to double my loop area. Since the Neodymium has a 5X gauss rating, at the distance from the strings I plan to have in my design, as the ceramic magnets, I figure I can get 10X the amount of inductance out of my primary loop.

Are you saying that using a stronger magnet gives you more inductance? That is not true. A stronger magnet can give you higher output, but if you use magnets much stronger than typical, you will affect the vibration of the string.

[bbsailor]

I have taken a couple of Alumitones apart, and rewound the secondary coils with about 300 turns each of 34 awg wire, then use a mic transformer at the amp. I'd have taken photos of the innards but i haven't got a camera. I've ruined a few $100 pickups over the years due to my insatiable need to open things up. But hey, i just rebuild them better!

But yeah, it's just what you think it is, a couple of plastic bobbins through which the c-shaped core laminations fit together, with many wraps of very thin wire on the bobbins, wrapped in tape, then the wire leads and ends of the bobbins and core are potted in epoxy. Actually i think the black shrink wrap is wrapped around first, the the epoxy poured in.

madzub,

Try this. Put a series/parallel switch between your two 300 turn coils made with AWG 34 wire. This should give you about a 200 to 800 ohm output variation and provide some tonal variation almost like switching humbucker coils between series and parallel.

What is the actual size of the two small bobbins? Also, tell us the bobbin wire window size and the approximate wire size used on the coils you took apart?

By putting the microphone matching transformer at the amp end of the cable, you are preserving the beneficial features (low noise and broad, flatter bandwidth) of low impedance transducers.

Joseph Rogowski

[Cashmaro]

BBSailor,
Thank you for joining the thread. I have read many of your posts and I am pleased to see someone who has more curiosity thanI do regarding this.

Mike,
I would like to retract that statement. After reviewing some electrical engineering literature, I see that Voltage output is related to magnetic flux per Faraday's Law. The permeability of NIB and ceramic magnets is the same, and thus no inductance difference. I want to research low pass filters to see how inductance shapes the curve.

I don't know if anyone is interested in the physics aspect of this, but I'd like to be able to make a spreadsheet or a MatLab program that can calculate output based on magnet flux, coil geometry, capacitance and resistance from a unit stringpluck. I'm sure there is more variables I am missing.

Some EE references that those interested may find useful:
Generated Voltage from Changing Magnetic Field
1.2.3 Faraday

I'll pick through my EE book from college. I'd like to be able to design a pickup and have an idea of the frequency response and voltage/amperage output to reduce guessing games.

Sorry for the digression.

The magnetic field can kill sustain apparently, as I didn't think of this before. It looks like the only real advantage of using NIB magnets is that you can use smaller ones to reduce spacial constraints.

Hopefully I get a chance to have the aluminum bracket design finished and machined soon so I can post a pic.

[Cashmaro]

I tried going through the math but its above me, the circuitry is complex. However, Lace's design is easy to calculate the math if simplified to an inductor in series with two inductors in parallel.

Is there somewhere I can buy a prewound coil on a small bobbin?

If not, is there somewhere that I can buy small bobbins for my wiring?

I was thinking instead of using two coil like Lace uses in his tertiary loops, to use one bobbin with 30 AWG wire and replacing the other coil with a small capacitor to kill noise? Anyone ever try use a capacitor with a wire going to ground?

[bbsailor]

I tried going through the math but its above me, the circuitry is complex. However, Lace's design is easy to calculate the math if simplified to an inductor in series with two inductors in parallel.

Is there somewhere I can buy a prewound coil on a small bobbin?

If not, is there somewhere that I can buy small bobbins for my wiring?

I was thinking instead of using two coil like Lace uses in his tertiary loops, to use one bobbin with 30 AWG wire and replacing the other coil with a small capacitor to kill noise? Anyone ever try use a capacitor with a wire going to ground?

Cashmaro,

The math for current transformers is rather simple. Use this web link to calculate the resistance of the primary string loop (either with copper or alumium)Resistivity Calc. Then simply multiply the square of the turns ratio by the primary thick string loop resistance, typically in micro-ohms. A 500 turn CSE-187L will have an output in the 250 ohm range using an AWG 10 wire loop (about 1000 micro-ohms with a simple magnet in the center): 250,000 times the string loop resistance. A Prem Magnetics SPCT-251 with 2000 turns will calculate by multiplying the primary loop resistance value by 2,000 squared or 4,000,000 times the string loop resistance. The SPCT-251 primary is open to accomodate a square copper AWG 4 wire that is .162" square available from Surplus Sales of Nebraska that measures out at about 26 micro-ohms per inch.

You can make your own CT based pickup very easy to learn how Lace voiced the various pickups in the Alumitone Series. The CSE-187L will match directly into an XLR 3-pin input to a mic mixer or a low to high Z mic matching transformer. Attach the CSE-187L transformer secondary to pins 2 and 3 on the XLR and attach pin 1 to the low impedance string loop and the CT metal frame to keep the noise as low as possible.

As you change the wire size of the string loop and choose various CT transformers with various turns ratios (500, 1000, 2000 etc) you can control the CT output impedance and the voicing of the output sound.

Keep experimenting. This is fun stuff!

Joseph Rogowski

[David Schwab]

My main question is what all the voodoo is in the shrinktube on the underneath of the alumitone. It looks like no one was willing to sacrifice one and take one apart, but who would a $100 a pop. It looks like 2 bobbins coiled with fine wire. I dont want to rip off his idea but I think understanding the concept helps.

It's a step up transformer.

David,
I was checking out your store and I see you use Neodymium in some of your pickups. What pull force is acceptable on my strings before funky things start happening? I tried using some online magnet calculatorsand it looks like the magnets I have pull with .11 lbs of force from a 3/8 inch space between the strings and the magnet. Is that too much?

I don't use neos directly under the strings because they pull too much. Maybe small ones would work fine.

[Cashmaro]

BBSailor,

I wasn't looking for resistance, thats pretty easy to calculate. The Low Z pickups aren't very resistive because there isn't much wire involved. I was looking for voltage and amperage output based on a unit stringpluck, which would be either an impulse or step function. The input doesn't matter so much, I just wanted to make sure the output was equivalent to Lace's design since they are both going to be on the same guitar. I drew up the circuits and intended to solve them using Ohm's law, but I need to add the string movement and use Faradays law as well. I'm not sure if anyone paying attention to this thread are into the engineering so much but if anyone is interested I will add it to this thread.

I have the bracket being machined now, it will look like Lace's for aesthetics but be 1/4 inch thick.

Where can I get the CSE-187L, XLR-3 and a mic mixer from for a good price?

Thanks for the input!

[bbsailor]

BBSailor,

I wasn't looking for resistance, thats pretty easy to calculate. The Low Z pickups aren't very resistive because there isn't much wire involved. I was looking for voltage and amperage output based on a unit stringpluck, which would be either an impulse or step function. The input doesn't matter so much, I just wanted to make sure the output was equivalent to Lace's design since they are both going to be on the same guitar. I drew up the circuits and intended to solve them using Ohm's law, but I need to add the string movement and use Faradays law as well. I'm not sure if anyone paying attention to this thread are into the engineering so much but if anyone is interested I will add it to this thread.

I have the bracket being machined now, it will look like Lace's for aesthetics but be 1/4 inch thick.

Where can I get the CSE-187L, XLR-3 and a mic mixer from for a good price?

Thanks for the input!

Cashmaro,

Post a photo of your bracket and tell us the type or metal you are using. If you are making it out of alumium, you will need to use "C-shaped" laminations to wind your miniature bobbins on. The best source for bobbins is: Cosmo Corporation - Coil Bobbin Catalog Main Menu .

The Triad CSE-187L current transformers are available form most large mail order electronics suppliers. The 3 pin XLR connectors are commonly availabe at Radio Shack. The Guitar Center has a single microphone channel microphone input mixer for about $40.00.

The output level is dependent on three variables. (1) Magnet strength, (2) The impedance of the primary string loop, (3) number of turns on the secondary coil or the turns ratio.

Obtain some current transformers, thick copper wire (household behind the wall wire is easy to find in many sizes from AWG 12 to AWG 8), packs of ceramic magnets available from Radio Shack, and thin copper tubing to make good solder joints between the CT primary leads and the string loop.

I have made up a special 10 foot cable (2-conductor shielded) connected to an XLR mic connector with alligator clips on the end to quickly try various current transformers. You can even use two CTs on each end of the string loop and then attach one to the mic input and the put a variable load (pot) on the other CT and change the impedance of the string loop and hear tonal variations with the second CT open, shorted or with a variable load.

Add your engineering analysis so others can jump in.

I hope this helps?

Joseph Rogowski

[Cashmaro]

BBSailor,
See pictures attached.

The bracket was made out of 6061 Aluminum bar stock. It was machined with endmills for the big cuts and the slots were made with a saw blade. I had a machinist buddy of mine make it in his spare time. The sharp corners were made with files, its rough but I haven't cleaned it up and sanded down the mill grooves yet. You can see it in comparison with the standard alumitone bracket on my guitar.

I have some aluminum weld wire I intend to use to grab current from the bracket, the same way Lace does.

My magnets are 1"x.25"x.125" thk neodymium iron boron magnets, N42. I realize I can boost my voltage output (and inversly impact amperage) by turns ratio : Vs/Vp=Ip/Is



I will refine my work in a later post.

Thanks for the help,
Cashmaro

[uneumann]

Many thanks for sharing some great info and ideas. I may have missed something in an earlier post, but it seems that a major advantage of LoZ is reduced (non-existent?) noise pickup due to electric fields. But what about magnetic fields? Don't these LoZ designs still pickup hum from transformers?

[bbsailor]

BBSailor,
See pictures attached.

The bracket was made out of 6061 Aluminum bar stock. It was machined with endmills for the big cuts and the slots were made with a saw blade. I had a machinist buddy of mine make it in his spare time. The sharp corners were made with files, its rough but I haven't cleaned it up and sanded down the mill grooves yet. You can see it in comparison with the standard alumitone bracket on my guitar.

I have some aluminum weld wire I intend to use to grab current from the bracket, the same way Lace does.

My magnets are 1"x.25"x.125" thk neodymium iron boron magnets, N42. I realize I can boost my voltage output (and inversly impact amperage) by turns ratio : Vs/Vp=Ip/Is



I will refine my work in a later post.

Thanks for the help,
Cashmaro

Cashmaro,

If you want to grab the current from the alumium bracket, you will need to obtain some "C-shaped" transformer laminations and feed them through two bobbins (about .75" long) connected in parallel. The resistance of each bobbin will need to be twice the rated Alumitone pickup resistance since the two coils are in parallel. I suspect you will need about 10,000 turns of AWG 48 to make a high impedance version to match other pickup output. If you go for a low resistance output, you will need between 50 and 70 ohms DC on each bobbin to match a low-Z input impedance.

Your biggest challenge will be to locate long "C-shaped" laminations to fit the thickness of the common node point and coil bobbins where the current from both low alumium coils passes through the interleaved laminations. Check the on-line catalog from Cosmo Corporation for bobbins.

Please share photos of how you design is progressing.

Thanks

Joseph Rogowski

[David Schwab]

Joseph, can't you connect the two coils in series?

[bbsailor]

Joseph, can't you connect the two coils in series?

David,

Yes, the coils can be connected in series but I believe the patent says that parallel is the preferred connection. Also, since we are dealing with a current transformer, a series connections that work well with voltage-based pickups are reversed (parallel connection) with current-based pickups. Current transformers with 500 up to 1000 turns ratios work well with impedances up to about 500 ohms (low-Z inputs). Generally, high impedance pickups work in an impedance range about 100 times (turns ratio squared) higher than low-Z pickups. This means that high impedance pickups have about 10 times more turns than low-Z pickups. These conclusions come from my experimentation and the application of transformer theory to current-based vice voltage-based guitar pickups.

If you have an Alumitone available, please measure the physical size and resistance of each coil or look at the coils and confirm how they are connected, series or parallel? Also, see if you can estimate the gauge of the wire being used. I suspect that they use AWG 46 to 48 wire to fit enough turns on the small bobbins.

Current transformer output impedance is closely related to the turns ratio squared times the DC resistance (impedance) of the primary loop. Assuming a 10,000 turn secondary, the impedance will be 100,000,000 times a few hundred microohms, the resistance of the primary alumium loop.

I hope I have answered your question?

Joseph Rogowski

[Mike Sulzer]

David,

Yes, the coils can be connected in series but I believe the patent says that parallel is the preferred connection. Also, since we are dealing with a current transformer, a series connections that work well with voltage-based pickups are reversed (parallel connection) with current-based pickups.

Joseph Rogowski

A current transformer is designed to sample the current in a circuit, affecting the circuit as little as possible. This means that it should have a very low impedance. This should be compared to some thing that samples voltage, which should have as high an input impedance as possible for the same reason: not to affect the circuit. You can use current transformers for other purposes than sampling current; they are useful when you are working at a very low impedance and want to step it up many times.

To use a current transformer as a current sampler you want to make sure that the impedance including that reflected back from the load on the secondary is very low compared to the impedance of the circuit connected to the primary. I do not think that you are doing that with the single turn pickup because its impedance is so low, and therefoe not much higher than the load placed on it by the transformer. I believe that you are just using it as a step up transformer, and so it is not necessary to conform to the connection topology that you would use when using it as a true current sensor.

[madzub]

Joseph,

I took some photos of the Alumitone guts with my webcam, not great shots but i'll post one. I'll also measure the bobbin size, tho the pickup is currently down at the shop so i'll get around to it tomorrow perhaps. I've rewound both my Alumitones, but I'm pretty sure the originals were wired in series, not parallel. The coil wire was very thin, felt like a fine fur after slicing it open, much finer than 42 awg, tho i don't think i could measure it accurately. I'll also be wiring one of the Lo-Z Alumitones up again soon -- they've been out of use for a while now waiting for a new guitar to be built -- and will try out a series-parallel switch, and let you know how the sound differs.

[David Schwab]

I've rewound both my Alumitones...

Was there a reason for that? Is that photo after it was rewound with larger gauge wire?

[bbsailor]

A current transformer is designed to sample the current in a circuit, affecting the circuit as little as possible. This means that it should have a very low impedance. This should be compared to some thing that samples voltage, which should have as high an input impedance as possible for the same reason: not to affect the circuit. You can use current transformers for other purposes than sampling current; they are useful when you are working at a very low impedance and want to step it up many times.

To use a current transformer as a current sampler you want to make sure that the impedance including that reflected back from the load on the secondary is very low compared to the impedance of the circuit connected to the primary. I do not think that you are doing that with the single turn pickup because its impedance is so low, and therefoe not much higher than the load placed on it by the transformer. I believe that you are just using it as a step up transformer, and so it is not necessary to conform to the connection topology that you would use when using it as a true current sensor.

Mike,

Thanks for jumping in. Generally, current transformer topology uses a low resistance burden resistor that must stay attached to the secondary to prevent a very high voltage from developing and arching out the secondary wire insulation. However, in a guitar pickup the current developed in the primary string loop is between 0.1A to about 0.3A and only a voltage of about a few hundred millivolts is developed on the secondary output. With a 250K volume pot load on the secondary and assuming a 10,000 turn secondary, reflects 2.5 milliohms back into the primary. The resistance of an alumium loop 0.125" thick by 0.25" wide and 7.5" long (about the Alumitone dimensions) equals 247.6 microohms using this calculator: Resistivity Calc .

The patent shows both series and parallel connections and notes a tonal variation with different coil connections. Generally, you want the volume pot value to be about 10 times the pickup output impedance. With a 10,000 turn secondary coil and about a 250 microohm string coil primary loop, you have a 25,000K ohm output impedance.

The thing that makes current transformer pickups interesting and different is the tonal variation or voicing you get when altering the resistance of the low impedance string loop that goes directly around the magnet. I reverse engineer my desired output impedance range by selecting the current transformer turns ratio, 500 to 1000 for low impedance pickups and 5000 turns for higher impedance outputs along with choosing the wire gauge that goes around the magnets.


Mike, do you feel that using thick alumium or copper as the primary loop creates eddy currents or skin effects that attenuates higher frequencies? Do you think that using Litz wire as the primary loops will improve the high frequency components?

Joseph Rogowski

[bbsailor]

Joseph,

I took some photos of the Alumitone guts with my webcam, not great shots but i'll post one. I'll also measure the bobbin size, tho the pickup is currently down at the shop so i'll get around to it tomorrow perhaps. I've rewound both my Alumitones, but I'm pretty sure the originals were wired in series, not parallel. The coil wire was very thin, felt like a fine fur after slicing it open, much finer than 42 awg, tho i don't think i could measure it accurately. I'll also be wiring one of the Lo-Z Alumitones up again soon -- they've been out of use for a while now waiting for a new guitar to be built -- and will try out a series-parallel switch, and let you know how the sound differs.

Madzub,

Thanks for the photo. When you measure the coil bobbins, try to measure the size of the wire window that is occupied by wire so that we can more accurately estimate the turns on each coil and reverse engineer the electrical characteristics of the pickup.

Bobbin inner length: ?
Bobbin inside square opening size for lamination to fit: ?
Bobbin outer flange size: ?
Bobbin wall thickness: ?


Joseph Rogowski

[madzub]

Was there a reason for that? Is that photo after it was rewound with larger gauge wire?

I rewound the first one after breaking a wire (it was very fine!) while trying to partly take it apart to see what was inside... I then rewound it following the Lo-Z info in another thread, and liked it so much that i intentionally rewound another working Alumitone. The originals didn't sound amazing to me, not bad, but like a regular pickup with less resonance, more clarity in the highs, but nothing more. The Lo Z version seems to have a lot more going on, greater dynamic range being the most important. I'll get it wired up again soon and do an A-B comparison with a regular pickup to compare accurately.

Yes. the photo is of the rewound pickup with 34 awg wire.

[Cashmaro]

BBSailor,

I see where you were going with the off the shelf transormers, an easy way to get a voltage boost (1000X with one, 2000X in series and some less in parallel) without adding a lot of resistance. This would not kill the high end, resulting in a very bright pickup.

I tried looking at the math, but from the looks of it it is a complex circuit that perhaps someone with an elictrical engineering degree could solve, however I am just not that great with electronics math. Bajaman had shown a circuit in one of the other threads, and its quite complex to derive a frequency response from. If I had access to some electrical engineering tools such as PSpics I would maybe be able to get what I was looking for with some help.

Lace is getting some 4000 ohms resistance, doing some math i found it would take about 8000 turns of 42 AWG wire with a mean turn diameter of .5 inch to get that resistance with both coils in series. I think it was about 111 ft of wire on each bobbin.

I am going the route of Madzub, I bought 100 Ft of AWG 30 wire and I planned on wrapping 2 bobbins with 50 ft each, which is about 350 turns each. I had one bobbin machined and wound it already. I attached an image of what i have so far and a 3D rendered image on my winding technique, it worked fairly well and I had little scatter winding. I have some steel weld wire which I planned on using in place of the C-shaped lamination. Since it is drawn steel it should have the grain directionality I am looking for but I will probably get some losses from eddy currents. This is a potential problem point.

All I need to do now is make another bobbin, wrap it and assemble and hopefully it sounds good. I was going to try wiring in series and parallel and see the differences. I will keep posting my progress as it comes.

Madzub,
Compared to the original alumitone, are you getting a better high end frequency response? Was the pickup quiter?

Thanks for more imput everyone,
Cashmaro

[bbsailor]

BBSailor,

I see where you were going with the off the shelf transormers, an easy way to get a voltage boost (1000X with one, 2000X in series and some less in parallel) without adding a lot of resistance. This would not kill the high end, resulting in a very bright pickup.

I tried looking at the math, but from the looks of it it is a complex circuit that perhaps someone with an elictrical engineering degree could solve, however I am just not that great with electronics math. Bajaman had shown a circuit in one of the other threads, and its quite complex to derive a frequency response from. If I had access to some electrical engineering tools such as PSpics I would maybe be able to get what I was looking for with some help.

Lace is getting some 4000 ohms resistance, doing some math i found it would take about 8000 turns of 42 AWG wire with a mean turn diameter of .5 inch to get that resistance with both coils in series. I think it was about 111 ft of wire on each bobbin.

I am going the route of Madzub, I bought 100 Ft of AWG 30 wire and I planned on wrapping 2 bobbins with 50 ft each, which is about 350 turns each. I had one bobbin machined and wound it already. I attached an image of what i have so far and a 3D rendered image on my winding technique, it worked fairly well and I had little scatter winding. I have some steel weld wire which I planned on using in place of the C-shaped lamination. Since it is drawn steel it should have the grain directionality I am looking for but I will probably get some losses from eddy currents. This is a potential problem point.

All I need to do now is make another bobbin, wrap it and assemble and hopefully it sounds good. I was going to try wiring in series and parallel and see the differences. I will keep posting my progress as it comes.

Madzub,
Compared to the original alumitone, are you getting a better high end frequency response? Was the pickup quiter?

Thanks for more imput everyone,
Cashmaro

Cashmaro,

Make sure that the steel weld wire that forms a loop through the alumium frame and the two coils is joined with a minimum gap so there is the maximum magnetic transfer for the highest output possible. Also, you may want to try using AWG34 to get more turns on each bobbin. Once you get it built, try to take some output voltage measurements. I suspect you will be in the 5 to 10 millivolt peak output range. An oscilloscope will allow you to see the peak voltage output easily. If you are planning to feed this output into a low impedance microphone mixer rated at 150 to 300 ohms (mic rating) that actual input impedance of the mixer will be about 2000 to 2500 ohms. You may want to try to get about 40 to 50 ohms DCR on each coil. Plan on grounding the alumium frame to reduce noise. If you can, please post an MP3 audio file of the final pickup.

There is no need to be heavly involved in math. Just post some basic measurements so others skilled in electronics and pickup theory on this forum can jump in and offer you some design alternatives.

If you measure the physical size of the alumium pickup primary string loop, calculate the loop's resistance and multiply that resistance in (micro-ohms) times the number of turns on the bobbin squared, you will get a close estimate to the output impedance. Using this on-line calculator http://www.salvarsan.org/pickups/ResistivityCalc.html I entered the total string loop length of 8 inches by .25 wide and .25 thick, selected the metal type (alumium) and found that to be 132 micro-ohms or .000132 ohms. 350 turns squared is 122,500 times .000132 equals 16.17 ohms.

I hope this helps,

Joseph Rogowski

[Cashmaro]

Cashmaro,

Make sure that the steel weld wire that forms a loop through the alumium frame and the two coils is joined with a minimum gap so there is the maximum magnetic transfer for the highest output possible. Also, you may want to try using AWG34 to get more turns on each bobbin. Once you get it built, try to take some output voltage measurements. I suspect you will be in the 5 to 10 millivolt peak output range. An oscilloscope will allow you to see the peak voltage output easily. If you are planning to feed this output into a low impedance microphone mixer rated at 150 to 300 ohms (mic rating) that actual input impedance of the mixer will be about 2000 to 2500 ohms. You may want to try to get about 40 to 50 ohms DCR on each coil. Plan on grounding the alumium frame to reduce noise. If you can, please post an MP3 audio file of the final pickup.

There is no need to be heavly involved in math. Just post some basic measurements so others skilled in electronics and pickup theory on this forum can jump in and offer you some design alternatives.

If you measure the physical size of the alumium pickup primary string loop, calculate the loop's resistance and multiply that resistance in (micro-ohms) times the number of turns on the bobbin squared, you will get a close estimate to the output impedance. Using this on-line calculator Resistivity Calc I entered the total string loop length of 8 inches by .25 wide and .25 thick, selected the metal type (alumium) and found that to be 132 micro-ohms or .000132 ohms. 350 turns squared is 122,500 times .000132 equals 16.17 ohms.

I hope this helps,

Joseph Rogowski

BBSailor,

I made the transformer bracket today by bending the weld wire, I was able to get a sharp corner by bending them over a thin plate and squeezing them with pliers. I ground and filed the ends flat so that they meet pretty well. From what I have read regarding transformer brackets, the closer the better. Would a thin layer of epoxy be good to make the separation?

Also, are the calculations taking into account any impedance from capacitance and inductance? Why would I want to boost the resistance so much, wouldn't it drop my voltage? I understand that more loops equals more output voltage, but there surely has to be a cutoff where the resistance overpowers the gain from additional turns? Also, if i did want more resistance couldn't i just put a resistor across the hot wire lead?

I chose AWG 30 wire because one of my co-workers made a really great bass pickup with AWG 30 wire (200 ft i think) and NIB magnets. It had a really low profile and he gave it to me to test out on my bass. I had never heard so much treble on a bass before, I was even able to run it through distortion and make it sound good.

Thanks again for the help. I have put a great deal of thought into this and cant wait to test this baby out. I will try to get some recordings with my Jamman and post comparisons to my BC Rich humbucker.

-Cashmaro

[bbsailor]

BBSailor,

I made the transformer bracket today by bending the weld wire, I was able to get a sharp corner by bending them over a thin plate and squeezing them with pliers. I ground and filed the ends flat so that they meet pretty well. From what I have read regarding transformer brackets, the closer the better. Would a thin layer of epoxy be good to make the separation?

Also, are the calculations taking into account any impedance from capacitance and inductance? Why would I want to boost the resistance so much, wouldn't it drop my voltage? I understand that more loops equals more output voltage, but there surely has to be a cutoff where the resistance overpowers the gain from additional turns? Also, if i did want more resistance couldn't i just put a resistor across the hot wire lead?

I chose AWG 30 wire because one of my co-workers made a really great bass pickup with AWG 30 wire (200 ft i think) and NIB magnets. It had a really low profile and he gave it to me to test out on my bass. I had never heard so much treble on a bass before, I was even able to run it through distortion and make it sound good.

Thanks again for the help. I have put a great deal of thought into this and cant wait to test this baby out. I will try to get some recordings with my Jamman and post comparisons to my BC Rich humbucker.

-Cashmaro

Cashmaro,

You can use thin super glue to keep the ends of the steel loop close together. Use any other means to accomplish the same objective.

My recommendations are based on the common input impedance of a passive microphone low-to-high matching transformers or the actual input impedance of a microphone mixer XLR input circuit between 2000 to 2500 ohms.

With current transformer guitar pickups, you need to think in terms of how many tenths of amps, yes 0.1A up to 0.5A are being generated in the low impedane string loop by the strings vibrating over the magnetic field. The lower the string loop resistance the more current is generated in the string loop and the more voltage is transformed into the secondary. Also, the more turns you have on the secondary, the more the output will be. It is all a balancing act to obtain the right output level (minimum noise also) and the right tone.

My only recommendation is to build it the way you plan, take measurements and post them and see if anyone has any ideas to make it better, if needed.

Now you are into the fun stuff where the real learning occurs!

Joseph Rogowski

[Cashmaro]

Finally got to wind the second coil. Basic assembly and soldering is about all that is left to do.

I rewound/wound to have 450 turns per coil. I am hoping this gives me the boost I am looking for. I bent the weld wire over a thin steel plate and clamped it with vice grips to get sharp corners at the connect from the primary loop.

I have one question regarding wiring. For in-series wiring, does the attached diagram look right? I think I have it correct but I just want to make sure. Sorry for the downgrade from 3d modeling to paint.

Also, Madzub, compared to a regular off-the shelf pickup, whas your re-wound pickup putting out the same volume levels at the same distance from the strings, or was it a little quiet? I know I can move it closer to the strings if need be, but too close and i will kill all of my sustain the the powerful NIB magnets.

I still need to record with the BC Rich pickups, will do soon.

Thanks,
Cashmaro

[bbsailor]

Finally got to wind the second coil. Basic assembly and soldering is about all that is left to do.

I rewound/wound to have 450 turns per coil. I am hoping this gives me the boost I am looking for. I bent the weld wire over a thin steel plate and clamped it with vice grips to get sharp corners at the connect from the primary loop.

I have one question regarding wiring. For in-series wiring, does the attached diagram look right? I think I have it correct but I just want to make sure. Sorry for the downgrade from 3d modeling to paint.

Also, Madzub, compared to a regular off-the shelf pickup, whas your re-wound pickup putting out the same volume levels at the same distance from the strings, or was it a little quiet? I know I can move it closer to the strings if need be, but too close and i will kill all of my sustain the the powerful NIB magnets.

I still need to record with the BC Rich pickups, will do soon.

Thanks,
Cashmaro

Cashmaro,

The only way the current generated in the primary string loop will reach the two small coils with 450 turns is through the magnetic field traveling through the steel wire core. This core should form a complete loop but with the ends butted well together with a minimum gap. File the ends flat and parallel so they fit together with a minimum gap between them. This will maximize the magnetic field to be as strong as possible and transfer the maximum energy to the two 450-turn coils. These coils should be wired in series adding. If the output is very low, just try reversing the phase of the series connection. You should have an output in the 10 to 20 millivolt range with two 450-turns coils in series. I am not sure how the steel rods will work as core material. If you have an oscilloscope, you can measure the output voltage very easily.

Post your results.

I hope this helps.

Joseph Rogowski