LoZ Pickups

[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[ATTACH=CONFIG]18975[/ATTACH][ATTACH=CONFIG]18975[/ATTACH][ATTACH=CONFIG]18976[/ATTACH]

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]

[ATTACH=CONFIG]19537[/ATTACH]

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

[Cashmaro]

Joe,
Thanks for the info. Was my wiring diagram correct or do I have it switched?

I was messing around with my Jamman today, never tried getting anything off it to the computer before. When I run my distortion pedal through it in series to my amp line-in, it sounds very computer-gamey. I had the same issue with my lightsnake when I was recording about a year ago.

I did get decent results by hooking it up to the line out on my amp (and luckily didnt fry the thing). Very feedbacky and extra distortion though.

I recorded some poorly executed riffs from Surfing with the Alien with my BC Rich original bridge pickup. For some reason, A string artificial harmonics wouldn't register but at the end the C string artificial harmonics sing. Can't explain that one.

How do I upload the wav files?

Thanks,
Cashmaro

[David Schwab]

How do I upload the wav files?

Your best bet is to upload them to a site like SoundCloud, and then post the link here.

[Cashmaro]

I got everything assembled, soldered and plugged in this weeked.

The end result was a muddy sound under distortion. Sounded pretty horrible. It was also about 1/4 as loud as my alumitone. I was hoping for it to be very bright, but at least I know one configuration that doesn't work.

At least I got some output. I figure I need to switch to a finer wire. I think I will try 38, 40 or 42 gage wire. With 42 gage wire I would get about 2300 ohms resistance.

I am not sure if the weld-wire transformer bracket contributed to the bad sound, and I am also unsure if the NIB magnetic field caused any disruption in the inductor coils, should I be shielding them from sensing magnets with a steel plate?

I'll take the whole thing apart and get some pictures when I set everything up again.

Thanks for the help so far!
Cashmaro

[bbsailor]

I got everything assembled, soldered and plugged in this weeked.

The end result was a muddy sound under distortion. Sounded pretty horrible. It was also about 1/4 as loud as my alumitone. I was hoping for it to be very bright, but at least I know one configuration that doesn't work.

At least I got some output. I figure I need to switch to a finer wire. I think I will try 38, 40 or 42 gage wire. With 42 gage wire I would get about 2300 ohms resistance.

I am not sure if the weld-wire transformer bracket contributed to the bad sound, and I am also unsure if the NIB magnetic field caused any disruption in the inductor coils, should I be shielding them from sensing magnets with a steel plate?

I'll take the whole thing apart and get some pictures when I set everything up again.

Thanks for the help so far!
Cashmaro

Cashmaro,

I suspect that the metal you choose to transfer the magnetic energy from the low impedance string loop to the smaller secondary coils is not too effective. See this web link for a good tutorial on audio transformers http://www.jensen-transformers.com/a...%20Chapter.pdf . The theory for audio transformers and current transformers (CT) is basically the same except that the CT has a much, much higher turns ratio. If the CT has 1000 turns on the secondary the impedance ratio will be 1000 X 1000 or 1,000,000. This puts the impedance ranges in the micro-ohm scale of resistance. Most transformers cores will have an Al value indicating the inductance factor for 1 turn. You will find most cores to be in the AL range of 2.5 to about 7 uH per coil turn. Since the primary string loop is a single turn on the primary the Al value indicates the level of core permeability; the higher Al value, the better.

There is not an issue with the core saturating as the current in the primary string loop will be in the range of 0.1 to 0.4A depending on the resistance of the low impedance string loop.

Look for "C-shaped" core sections. Radio Shack has a 600 to 600 ohm matching transformer that is you could disassemble so you could slip it through the primary string loop to make a more efficient magnetizing field match. Lace makes their Alumitones this way so the laser cut alumium frame maintains a good, low conductivity string loop. The connection to the secondary coil(s) is through the small laminated "C-shaped" lamination cores interlocked through the alumium frame. The short piece of the alumium frame that passes through the "C-shaped" laminations is the single primary loop of 1 turn. The amount of turns on the secondary than equals the turns ratio.

Post photos of what you have done so far.

I hope others like Mike Sulzer and/or Joe Gwinn jump in to offer more advise.


Joseph Rogowski

[Cashmaro]

Been along time but I started working on this again a few months ago, I wanted to test a few things.

The first thing I did was ditch the steel transformer bracket, so I drilled a hole in the aluminum body and press fit a copper rod directly into it. I measure about 1 ohm resistance, as a check to make sure I am getting current flow. This is similar to the method proposed by BB Sailor and used by Bajaman on his bass pickup. I rewound the bobbin to 2000 turns with 40 AWG wire and fit it onto the copper post, checked resistance and got about 170 ohm.

I plugged in and I did get output, however I have to crank my 300 watt bass amp to 10 to get enough sound to hear it coming out of the speaker (a stack of 4 different cabs at about 5 ohm impedance).

I next wound a copper wire, 10 turns, around the neo-magnet and fed one end through the bobbin. Checked again on my amp, same effect as before.

I found a 2000 turn current sensor on amazon, which in theory should have 4 times the output of the AS-104 sensors mentioned in other threads.
Amazon.com: 0-5A Input Current Transformer Sensor TA12L-200: Industrial & Scientific

The plan is to replace the pickups on my p-bass, but I want to get something with decent output. Another thought I had was to do a double step-up, by using one current transformer to step up off the bracket, then another off the leads from that sensor to step up again. So 1:10, then maybe 1:2000 to get a total step up of 20000. I am at a sticking point now, any suggestions to help boost output?

[bbsailor]

Been along time but I started working on this again a few months ago, I wanted to test a few things.

The first thing I did was ditch the steel transformer bracket, so I drilled a hole in the aluminum body and press fit a copper rod directly into it. I measure about 1 ohm resistance, as a check to make sure I am getting current flow. This is similar to the method proposed by BB Sailor and used by Bajaman on his bass pickup. I rewound the bobbin to 2000 turns with 40 AWG wire and fit it onto the copper post, checked resistance and got about 170 ohm.

I plugged in and I did get output, however I have to crank my 300 watt bass amp to 10 to get enough sound to hear it coming out of the speaker (a stack of 4 different cabs at about 5 ohm impedance).

I next wound a copper wire, 10 turns, around the neo-magnet and fed one end through the bobbin. Checked again on my amp, same effect as before.

I found a 2000 turn current sensor on amazon, which in theory should have 4 times the output of the AS-104 sensors mentioned in other threads.
Amazon.com: 0-5A Input Current Transformer Sensor TA12L-200: Industrial & Scientific

The plan is to replace the pickups on my p-bass, but I want to get something with decent output. Another thought I had was to do a double step-up, by using one current transformer to step up off the bracket, then another off the leads from that sensor to step up again. So 1:10, then maybe 1:2000 to get a total step up of 20000. I am at a sticking point now, any suggestions to help boost output?

Cashmaro,

If you use the TA12L-200 Current Transformer (CT) with 2000 turns, the output impedance will be the resistance of the primary string loop (with the magnet in the center) times 4,000,000 or 2,000 squared. If you make the string loop out of AWG 6 which is 0.162" diameter and 32.9 micro-ohms per inch that is 6" long, the total resistance will be 197.4 micro-ohms. The output impedance would be 197.4 times 4,000,000 is 789.6 ohms plus about 100 ohms caused by leakage inductance. The output of this 2000 turn CT should be between about 10 to 20 millivolts to feed a Mic input but not enough output to directly feed the high impedance amp input directly. Go through a mic step up or matching transformer located near your amp.

If you use a thicker wire such as AWG 4 you will need to file the center of the toroid center hole a little wider to accomodate the thicker AWG 4 which is .2043" diameter and 20.7 micro-ohms per inch, but the hole in your toroid is 0.196. This AWG 4 wire will make the output impedance now about 496.8 ohms plus about another 100 ohms for leakage inductance. This would make a little better input match for the mic matching transformer and produce about a 10 to 12 times voltage boost, depending on the specific mic matching transformer that you use.

The real challenge is bending this thick wire without breaking the toroid and joining together the primary loop with about .375" length of copper tubing to make a low resistance joint to make the maximum current in the primary loop. It helps if you have something like the Extech LCR Meter to monitor the output impedance of the toroid with the primary loop secured and soldered.

Post a photo of what you are trying to do.

I hope this helps.

Joseph Rogowski

[Cashmaro]

BB Sailor,
In short, current sensors or step up transformer magnify the primary loop impedance by number of turns - squared. So, I am getting huge resistance, causing the low output. Is this correct? Would the 500 turns of the Talema AS-104 be better suited since the magnification of impedance would be lower, although voltage gains from number of turns less?

I think I can do one better with a basic rotary tool to grind, some copper bar stock and a vice. There should be almost no resistance in that loop, and I can make good solder joint.

I see you use the match-mic transformer, which appears to be a reliable way to boost voltage. Is there a way I can avoid this? Lace does not need this transformer.

I will get photos when I figure out why I cannot upload! Does it have something to do with filenames?

[bbsailor]

BB Sailor,
In short, current sensors or step up transformer magnify the primary loop impedance by number of turns - squared. So, I am getting huge resistance, causing the low output. Is this correct? Would the 500 turns of the Talema AS-104 be better suited since the magnification of impedance would be lower, although voltage gains from number of turns less?

I think I can do one better with a basic rotary tool to grind, some copper bar stock and a vice. There should be almost no resistance in that loop, and I can make good solder joint.

I see you use the match-mic transformer, which appears to be a reliable way to boost voltage. Is there a way I can avoid this? Lace does not need this transformer.

I will get photos when I figure out why I cannot upload! Does it have something to do with filenames?

Casmaro,

Yes, the low output can be caused by haveing a too high resistance in the string loop, That is why I posted the anticipated output impedances with common copper wires in the micro-ohm range for the primary string loop.

Use this web site to calculate the resistance of your alumium frame. Resistivity Calc > Alumium has a higher resistance than copper so be sure to change the metal type in your calculations at the bottom of the screen. The copper pin going through your metal frame and the current transformer (CT) must have a very,very,very,very good connction to allow the current to be at maximum. Believe it or not, but the current in the primary string loop can be between .1 to .2 amps. But this higher current only works when the total resistance in the string loop in the 300 to 500 micro-ohm range. A 500 turn CT with a 300 microohm string loop will have about a 75 ohm impedance calculated output but the measured impedance wil be about 25 ohms higher due to transformer leakage inductance. This 500 turn CT will match very well with a passive mic input transformer or mic mixer using an XLR input. By placing the mic matching transformer near the amp you eliminate the coax capacitance effect that causes high frequency attenuation on high impedance guitar pickups. True, Lace did not design the Alumitone this way, but they make their two coils with about 10,000 turns each of about AWG 48 wire to have an output near high imnpedance pickups. I believe the coils are wired in parallel to properly load and voice their new type of pickup into a high impedance input like a guitar amp. The Shure A95U mic matching transformer has a 1 to 12 turns ratio which means that for a source impedance in the 100 to 300 ohm range, the transformer will have about a 12X voltage gain making the total turns ratio about equal to 6000 turns. There is a big however, and that is the input impedance of your source. The actual input transformer has an actual input impedance near 3000 ohms to act as a bridging input of 10X the source impedance to not load down the voltage too much., If the source impedance matches the input impedance, there will be a 6db voltage drop so using current with more than about 1000 turns will start changing the tone of your pickup as the less than optimal source to input matching will act as a tonal filter. See Les Paul recording guitar and the Jack Casady low impedance bass with the 3-position impedance switch.

Try a 500 to 1000 turn (absoulte maximum) and ensure that the total string loop resistance stays in the lower microhm range of 200 to 500 microohms favoring the 200 to 300 microohms range with a 1000 turn CT.

When you examine a commercial Lace Alumitone pickups, notice how the alumium primary string loop is stamped out of a single piece of alunium about .125" thick and then bent into the final shape. There is no joint as the alunium loop is continuous. Lace choose to link the secondary of the CT by using the metal frame of the primary string loop going through a series of interlocking "C-shaped" laminations with the short section of the amumium frame being the current carrying source of inductance. On this "C-shaped" lamination are two barrel type coils that act as the CT secondary.

Assuming that the Lace Alumitone has 10,0000 turns on each coil wired in parellel we can use 5000 turns as a parallel, noise cancelling equivalent and if the pickup has a 2500 ohm output impedance, then the alumium frame must have a resistance in the range of 2,500 ohms divided by 5,000 squared or about 100 microohms.


When dealing with current based pickups, the maximum current generated in the string loop will produce a higher output but this maximum current requires really, really, really, really low string loop impedances. That is why I emphasize making a good low impedance loop joint using copper tubing, sanding the interior of the copper tubing and soldering with silver solder to obtain the lowest primary string loop impedance.
With an alumium frame, you need to use a very, very, very, very low resistance way to pass the current through the toroid CT center opening.


The skills in making low impedance pickups is all about making the shift from voltage based high impedance pickup thinking to the transformer action of an extremly high turns ratio transformer into the mechanics of fitting appropriate commercially available CTs and mic matching transformers into a pickup designed to fit typical guitar or bass pickup footprint. It requires mechanical creativity and the encouragement of personal experimentation successes by following my recommendations and reading up about transformer theory. Obtaining a Extech LCR meter is good to have to see the effect of attaching a particular CT to a particular string loop micro-ohm impedance.

Keep up the good work!. Experimenting is learning.

I hope this helps?

Joseph Rogowski