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Post by antigua on Dec 4, 2016 0:38:32 GMT -5
www.lacemusic.com/alumitone_single_coil.php![]()  ![]() The patent can be seen here www.google.com/patents/US5831196?dq=5831196 , though it differs a little from the actual pickup. Unlike most pickups that form a high impedance and generate a current with the same coil, or coils, the Lace Alumitone is a low impedence "current driven" pickup that creates a high impedance with a little transformer hidden under the ceramic and aluminum face. The layout is like an "8", with the transformer coupling at the center crook of the eight. So, in essence, it's like a Seymour Duncan Vintage Rails, with the split rail layout, and instead of generating a current and a voltage with coils alone, the Alumitone divides the task up among two parts: the aluminum structure supplies the current, and a little transformer underneath creates a usable voltage. Tone wise, they are flat, but also have a fairly low cut off, so they have a hotter disposition. Lace Alumitone #1
DC Resistance: 2.508K
Inductance: 26.52H @120hz, 5.235H @1khz
Lace Alumitone #2
DC Resistance: 2.514K
Inductance: 28.90H @120hz, 5.100H @1khz
Lace Alumitone #3
DC Resistance: 2.519K
Inductance: 31.39H @120hz, 5.425H @1khz
Resonant Peak: dV: 7.8dB f: 7.99kHz
Loaded (200k & 470pF): dV: 3.0dB f: 2.64kHz
Gauss 1050 - 1150 south faces, 900 - 950 north facesBode plot (three different Alumitone plots, overlapped)  Electrical considerations...One thing that is clear to see is that there is very little resonance, most like due to core eddy currents. The coil's core is laminated, as can be seen in the picks below. The knee is very soft. The flatness of the reactance speaks to the clarity, and "modern" tone these pickups are known for. These pickups are also know for not being too smooth with tone controls, and with a knee that is already soft, a tone control will cause the pickup to become dark more quickly, and where as most tone controls rebound with a nice, new resonance at zero on the tone dial, these pickups will have no such resonance, and so they will just sound dull at zero. A selective capacitor type tone control, such as the Stellartone ToneStyler, would be more effective for this type of pickup. These are the values Lace lists for the "single coil" Alumitones on their website: Resistance: 2.5k
Peak Frequency: 2343
Inductance: 3.0 henriesMy resistance measure agrees with their resistance measure, though I measured a peak resonances at 8.0kHz, which is miles above the 2,343Hz they listed, although my loaded peak frequency is rather closeat 2.64kHz, so it's possible, if not likely, that Lace acquired this peak resonance while the pickups were loaded into a guitar, probably one that contains two 250k pots. I had trouble getting a believable inductance measure with the Extech 380193 LCR meter. Based on the loaded peak resonance of 2.64kHz with 470pF added capacitance, it's likely that the inductance is north of 5H. Without knowing the capacitance of the pickup, it's hard to say, and since it's so unlike any other pickup out there, I can't even take a wild guess. Magnetic considerations...It is a humbucker; external noise is generated in the aluminum "8", and the current approaches the mutual transformer core from both sides at the same time, so they cancel out, while the guitar strings have a magnet to only one side of the "8", so the current they generate is not cancelled out (at least not nearly as much). For stylistic reasons, they have two magnets on either side, with opposite polarities, three strings to a magnet. The two offset magnet circuit is not unlike a Fender "Wide Range Humbucker", this just looks a lot more futuristic. They also have a "Deathbucker" and a bass guitar version that use two magnets all the way across the length of the pickup, and in the sense that they magnetize the string in two places, in two different polarities, makes their aperture similar to a PAF style humbucker. There are a lot of ways it can be done, likely with very similar results, so the layout of magnets and conductive metal is probably more of an aesthetic choice. There are extra strips of ferrous material underneath the magnets, maybe to strengthen the magnetic fields, because even though this is ceramic, they don't have a lot of depth. The ceramic bar magnet / ferrous strip over the transformer produces over 1050G along the top, while the other side generates around 950G. The difference is not great enough to audibly impact the output levels, though. The magnetic aperture with respect to the strings is about as wide as a Strat pole piece, though it's homogeneous along it's length, like a rail pickup. And. whereas a Strat pickup has pole pieces all in a straight line, the magnets here are offset in a way that reads the wound strings more towards the neck, and the plain strings more towards the bridge. It probably doesn't matter for a pickup this narrow, but it's probably significant in the case of the the larger "humbucker sized" Alumitone with the offset magnets, which offsets the wound and plain strings by about a centimeter. The "coil" in this case, is also a lot closer to the strings that with a Strat pickup or PAF, since there is no plastic bobbin, or cover, in between. The coil is also also a lot more shallow. Where as a Strat's bobbin is 12mm tall, or a PAF's is 7mm tall, the Alumitone's aluminum coil is is just under 3mm in thickness, so the way flux passes through the conductive cross section as the string move vibrates will be different, though I'm not sure what tonal difference this makes, if any. It would probably require some FEM modelling to determine how the sum of flux differs between one coil geometry and another, with respect to the position of the guitar string. Overall, I think they're an interesting offering. People say they sound clear, but IMO, and as the resonant peak alludes to, they're bolder sounding pickups. Images:
  I found some images out there on the 'net. A user named michaelwayneharwood at TalkBass.com already took the time to rip one apart, saving me the hassle: www.talkbass.com/threads/low-impedance-low-noise-pickups-research-whats-the-skinny.1144113/page-3 
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Post by ms on Dec 4, 2016 8:23:55 GMT -5
In understanding a pickup such as this, I think it is important to emphasize how the law of magnetic induction applies equally to all pickups. The law says that a voltage is induced around a path. In a multi turn coil, the voltages of the individual turns naturally appear in series. This is a simple, effective, and elegant way to achieve a higher voltage, and it is hard to believe that a single turn pickup has any advantage other than novelty. And it has some significant practical disadvantages, mainly how to handle the very low impedance without extra loss.
Current flows when a load is attached, no matter how many turns you have, and how much current can flow is limited by the properties of the coil, both its resistance and inductance. You can work out the scaling. The same power is available with any number of turns if the permeability of the core is the same, and the same space is filled with the turns. (Fewer turns have less resistance linearly, but you can use larger wire and so you get a squared relationship, always obtaining the same effective resistance for copper with any number of turns in the same space. The inductance varies as the square of the number of turns for turns in the same space, and so both parameters lead to constant available power, which goes as the square of the voltage.)
I suspect that the low Q is at least partly a result of higher effective resistance. Not only does the "coil" occupy less space the a normal pickup, and so has a higher effective resistance, it is very difficult not to incur extra losses with such a low impedance.
Magnetic noise is not canceled as you say. The changing flux of the noise field through the coil induces voltage around the turns. Cancellation must be specific here as in a normal hum bucker. In this case you also have the potential to induce hum directly in the transformer. This is why transformers intended for low level audio are normally shielded. Here it appears that a hum bucking transformer has been created instead of using a shield. This appears to be part of a system in which the signals into the two coils add while the hum subtracts, but I have not worked out the details.
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Post by antigua on Dec 4, 2016 16:01:17 GMT -5
And it has some significant practical disadvantages, mainly how to handle the very low impedance without extra loss. I understand they use aluminium to keep the resistance very low, is resistivity the sort of loss you're referring to? Current flows when a load is attached, no matter how many turns you have, and how much current can flow is limited by the properties of the coil, both its resistance and inductance. You can work out the scaling. The same power is available with any number of turns if the permeability of the core is the same, and the same space is filled with the turns. (Fewer turns have less resistance linearly, but you can use larger wire and so you get a squared relationship, always obtaining the same effective resistance for copper with any number of turns in the same space. The inductance varies as the square of the number of turns for turns in the same space, and so both parameters lead to constant available power, which goes as the square of the voltage.) If a typical coil is a lot of turns in series, isn't this essentially a similar number of turns in parallel? I suspect that the low Q is at least partly a result of higher effective resistance. Not only does the "coil" occupy less space the a normal pickup, and so has a higher effective resistance, it is very difficult not to incur extra losses with such a low impedance. Does this mean that a thicker aluminium structure would, or should, have a higher Q factor? Magnetic noise is not canceled as you say. The changing flux of the noise field through the coil induces voltage around the turns. Cancellation must be specific here as in a normal hum bucker. In this case you also have the potential to induce hum directly in the transformer. This is why transformers intended for low level audio are normally shielded. Here it appears that a hum bucking transformer has been created instead of using a shield. This appears to be part of a system in which the signals into the two coils add while the hum subtracts, but I have not worked out the details. I'm not real clear on this part of it. This forum allows editing of posts indefinitely, so I'll remove information that is incorrect so that the first post is not misleading. I'm not entirely clear as to whether the low impedance of the primary coil is low-noise due to the fact that it is low impedance. As you said earlier, voltage is induced around a path, and here I count three paths, one around the entire perimeter, and two paths on either side. That being the case, the current running through the middle of the "8" should be cancelling, because they two outer paths are meeting there, going in opposite directions. Then they arranged it so that the string induces current on only one side of the "8" or the other, so that where it meets the transformer at the middle, it is not cancelling itself out. That looks to me like a humbucking arrangement right there, but no, I don't have a firm grasp of all that is going on there. It makes sense to me that the transformer is a humbucker in its own right, to prevent noise from entering the circuit there, but I figured that if the aluminum "8" served not technical advantage, they would just do the single "0" loop, as was depicted in the patent www.google.com/patents/US5831196?dq=5831196 The patent says " It should be appreciated that the sensor assembly 10 may be configured to act as a humbucker or a noise compensating single coil." Schematic #10 is below:  |
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Post by stratotarts on Dec 4, 2016 16:36:54 GMT -5
Edit: There is hum cancellation in the secondary, but not the primary and also in the primary. It took me a while to see it.
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Post by antigua on Dec 4, 2016 16:43:35 GMT -5
Is the "8" and the offset magnets really cosmetic then? I find that hard to believe. If that were the case, the final design could match the patent drawings, with a long "U" single turn, it would have been cheaper to produce, and supposedly still hum cancelling. Another variation of the Alumitone has two bars that extend along the length. Presumably, the magnets are opposite polarities, so that when the string induces and the currents meat in the middle, the phases are complimentary rather than cancelling.  |
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Post by ms on Dec 4, 2016 18:40:10 GMT -5
"I understand they use aluminium to keep the resistance very low, is resistivity the sort of loss you're referring to?" Copper would be significantly lower, but yes it is restive loss that i refer to. "If a typical coil is a lot of turns in series, isn't this essentially a similar number of turns in parallel?" Yes, that is one way to think about a single low resistance turn. "Does this mean that a thicker aluminium structure would, or should, have a higher Q factor?" I think so, but there probably are other factors involved as well. "I'm not real clear on this part of it. This forum allows editing of posts indefinitely, so I'll remove information that is incorrect so that the first post is not misleading. I'm not entirely clear as to whether the low impedance of the primary coil is low-noise due to the fact that it is low impedance. As you said earlier, voltage is induced around a path, and here I count three paths, one around the entire perimeter, and two paths on either side. That being the case, the current running through the middle of the "8" should be cancelling, because they two outer paths are meeting there, going in opposite directions. Then they arranged it so that the string induces current on only one side of the "8" or the other, so that where it meets the transformer at the middle, it is not cancelling itself out. That looks to me like a humbucking arrangement right there, but no, I don't have a firm grasp of all that is going on there. " It makes sense to me that the transformer is a humbucker in its own right, to prevent noise from entering the circuit there, but I figured that if the aluminum "8" served not technical advantage, they would just do the single "0" loop, as was depicted in the patent www.google.com/patents/US5831196?dq=5831196 The patent says " It should be appreciated that the sensor assembly 10 may be configured to act as a humbucker or a noise compensating single coil." Schematic #10 is below:" Low impedance reduces electrical noise, as does shielding with a conductor. Magnetic noise must be canceled; if you shield with magnetic material, you will affect the signal as well. I do not see a path all the way around the perimeter; I see a cut on one end that interrupts it and dangerously assume that the other end is configured to make the following explanation work. I agree that the purpose of the "8" is to allow hum bucking performance. I think it effectively makes two loops, one for the wound strings and the other for the plain strings. I think it is just a matter of getting the signals to the transformer coils in such a way that the voltages from the changing flux of hum fields cancel. My assumption is that the protruding parts of the transformer cores visible in the disassembled photo stick through the loops on the end where they bend "vertical", enabling the primary excitation when assembled. Then you can see how the loop on the side away from the transformer excites flux through the core. The black stuff might be hiding something we need to see in order to understand how the close side loop is connected. This would imply that each loop has its own transformer, connected together in order to mutually cancel their hum pickup. As you noted earlier, the transformer cores are laminated, and I think this eliminates eddy currents in the transformer as an issue. |
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Post by ms on Dec 4, 2016 18:49:18 GMT -5
There is hum cancellation in the secondary, but not the primary. That is a possibility, but in this way can you cancel both the hum from the loops and the hum pickup from the transformer coils? I think you need control over the phase at both the primaries and the secondaries to do both. (But I will think about this no more for a while!) |
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Post by antigua on Dec 5, 2016 1:55:25 GMT -5
I do not see a path all the way around the perimeter; I see a cut on one end that interrupts it and dangerously assume that the other end is configured to make the following explanation work. I agree that the purpose of the "8" is to allow hum bucking performance. I think it effectively makes two loops, one for the wound strings and the other for the plain strings. I think it is just a matter of getting the signals to the transformer coils in such a way that the voltages from the changing flux of hum fields cancel. My assumption is that the protruding parts of the transformer cores visible in the disassembled photo stick through the loops on the end where they bend "vertical", enabling the primary excitation when assembled. Then you can see how the loop on the side away from the transformer excites flux through the core. The black stuff might be hiding something we need to see in order to understand how the close side loop is connected. This would imply that each loop has its own transformer, connected together in order to mutually cancel their hum pickup. As you noted earlier, the transformer cores are laminated, and I think this eliminates eddy currents in the transformer as an issue. I'm not sure where you see a cut, it looks to me like a fully continuous "8" shape. This is my understanding: when the magnetic flux increases due to the moving string closer to the pickup, the current would travel one direction or another, depending on the polarity of the of the magnet, but since the magnet is to one side of the 8 or the other, current would flow down one direction on the magnet's side of the 8, and flow up the other direction though the center and the farther side of the 8. So in that respect, it would be a loop around the whole perimeter of the pickup. But the transformer core only wraps around the center of the "8", so it will only (mostly) see current travelling through the middle of the 8, and not that which travels around the outside. Magnetic noise would hit the "8" at some angle, and it would induce currents around the entire perimeter of the 8, as well as around the two side loops of the 8, and in the middle of the 8, they would be meeting each other in opposite directions and cancel out, and it's at that point where the current is tapped into by the transformer. If the transformer were around either of the two outer loops alone, it would not humbuck because it would never see that cancelling current from the other side of the 8, coming in the other direction. The fact that the ceramic magnets are to one side of the 8, or the other, is what allows the current from the strings to not cancel out in the middle. Therefore, I don't think you have to have two secondary coils to get EMI cancellation from the primary, the secondary only has to be a humbucker so that the secondary doesn't itself become a source of noise. This makes sense in my mind, so let me know if I'm getting my facts wrong. If I visualize the Alumitone as being bent into a tall, straight strip of metal, sticking straight out of the guitar, we then have what looks like a traditional transformer, with the primary and secondary side by side, with a shared core. The 8 shape just means that some of the induced current in the single turn is 180 degree out of phase with itself, and cancelling, while some of the current remains intact and get passed along to the secondary. |
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Post by ms on Dec 5, 2016 7:05:35 GMT -5
I'm not sure where you see a cut, it looks to me like a fully continuous "8" shape. This is my understanding: when the magnetic flux increases due to the moving string closer to the pickup, the current would travel one direction or another, depending on the polarity of the of the magnet, but since the magnet is to one side of the 8 or the other, current would flow down one direction on the magnet's side of the 8, and flow up the other direction though the center and the farther side of the 8. So in that respect, it would be a loop around the whole perimeter of the pickup. But the transformer core only wraps around the center of the "8", so it will only (mostly) see current travelling through the middle of the 8, and not that which travels around the outside. Magnetic noise would hit the "8" at some angle, and it would induce currents around the entire perimeter of the 8, as well as around the two side loops of the 8, and in the middle of the 8, they would be meeting each other in opposite directions and cancel out, and it's at that point where the current is tapped into by the transformer. If the transformer were around either of the two outer loops alone, it would not humbuck because it would never see that cancelling current from the other side of the 8, coming in the other direction. The fact that the ceramic magnets are to one side of the 8, or the other, is what allows the current from the strings to not cancel out in the middle. Therefore, I don't think you have to have two secondary coils to get EMI cancellation from the primary, the secondary only has to be a humbucker so that the secondary doesn't itself become a source of noise. This makes sense in my mind, so let me know if I'm getting my facts wrong. If I visualize the Alumitone as being bent into a tall, straight strip of metal, sticking straight out of the guitar, we then have what looks like a traditional transformer, with the primary and secondary side by side, with a shared core. The 8 shape just means that some of the induced current in the single turn is 180 degree out of phase with itself, and cancelling, while some of the current remains intact and get passed along to the secondary. I was misunderstanding what periphery you meant, but that does not change what I am saying. There must be a continuous very low impedance path through which changing flux from the vibrating string passes, and which results in changing flux through the transformer core. Thus this path must go around the transformer core. The only way I can see this happens is if the end of the core sticks through the path. This appears to be the case at the end of the pickup where the protruding part of the core appears to stick through the path where it bends over the end of the pickup. I do not see how this happens near the middle of the eight. This path describes how the strings further from the end where the transformer is located are sensed, as seen in the picture of the disassembled pickup. Once this path is identified, it is apparent that there must be another path for the strings closer to the pickup. I cannot see all of it, but it appears that it is a similar path. |
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Post by newey on Dec 5, 2016 7:18:53 GMT -5
Antigua-
Yes, but there's a right way and a wrong way. We ask that all edited material be noted as such, with an explanation of the reason for the edit. For example, you can use red typeface for the new material, but leave the old material in place. Or, use the "strikethru" feature to cross out the old mnaterial, then add the new. At the bottom, the forum software will indicate the time/date of the last edit, and you can add to that something like "edited by antigua to correct misstatement" or some such.
In this way, later readers get the new info in the first post, but the following posts still make sense. Here, for example, if you (silently) change the first post to correct any misstatements, then a later reader can't make sense out of ms's reply to you, which refers to the original version of your post.
So, edit away, but please don't do so without explicit notice.
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Post by antigua on Dec 5, 2016 12:53:28 GMT -5
I was misunderstanding what periphery you meant, but that does not change what I am saying. There must be a continuous very low impedance path through which changing flux from the vibrating string passes, and which results in changing flux through the transformer core. Thus this path must go around the transformer core. The only way I can see this happens is if the end of the core sticks through the path. This appears to be the case at the end of the pickup where the protruding part of the core appears to stick through the path where it bends over the end of the pickup. I do not see how this happens near the middle of the eight. This path describes how the strings further from the end where the transformer is located are sensed, as seen in the picture of the disassembled pickup. Once this path is identified, it is apparent that there must be another path for the strings closer to the pickup. I cannot see all of it, but it appears that it is a similar path. When I say the middle of the 8, I mean that can be anywhere along the length of the portion of aluminum that is central. In the patent they call that the "center leg". It happens to be that the transformer core wraps around the far end of the center leg. Since the phases of EMI cancels out at any point along the center leg, it doesn't matter where the transfomer's core intersects with it. I'm not sure what you mean by the further strings requiring a separate path, because for example, this version of the pickup has all six strings utilizing both routes that the current can take, by having reverse magnetic polarities, like a typical humbucker: The difference with the split-magnets version on the Alumitone that I have on hand is just that they arbitrarily decided to magnetically polarize the guitar string in one location instead of two, so it so happens that three string use one route, and the other three use the other. On the example I have on hand, the polarities of the magnets are reversed, but since the strings are only being charged by one magnet or the other, the two magnets could be of the same polarity, and it would still work fine. I suppose that making the two split magnets opposite polarities helps prevent a dead spot if you are bending the string in the middle of the pickup, between the two magnets. You said some details that you're unsure of are not made clear by the pictures of the disassembled Alumitone, do the patent drawings illustrate the unseen feature you're referring to? Just so it is known, the patent does say explicitly that the inventor believes the "8" figure induces hum cancelling: "It should be appreciated that the shape of the primary winding 320 produces a hum canceling effect due to the current flow therethrough."
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Post by antigua on Dec 5, 2016 12:59:46 GMT -5
Antigua- Yes, but there's a right way and a wrong way. We ask that all edited material be noted as such, with an explanation of the reason for the edit. For example, you can use red typeface for the new material, but leave the old material in place. Or, use the "strikethru" feature to cross out the old mnaterial, then add the new. At the bottom, the forum software will indicate the time/date of the last edit, and you can add to that something like "edited by antigua to correct misstatement" or some such. In this way, later readers get the new info in the first post, but the following posts still make sense. Here, for example, if you (silently) change the first post to correct any misstatements, then a later reader can't make sense out of ms's reply to you, which refers to the original version of your post. So, edit away, but please don't do so without explicit notice. Of course, if for no other reason than to give credit where credit is due. |
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Post by ms on Dec 5, 2016 14:24:34 GMT -5
I'm not sure what you mean by the further strings requiring a separate path, because for example, this version of the pickup has all six strings utilizing both routes that the current can take, by having reverse magnetic polarities, like a typical humbucker: The difference with the split-magnets version on the Alumitone that I have on hand is just that they arbitrarily decided to magnetically polarize the guitar string in one location instead of two, so it so happens that three string use one route, and the other three use the other. On the example I have on hand, the polarities of the magnets are reversed, but since the strings are only being charged by one magnet or the other, the two magnets could be of the same polarity, and it would still work fine. I suppose that making the two split magnets opposite polarities helps prevent a dead spot if you are bending the string in the middle of the pickup, between the two magnets. You said some details that you're unsure of are not made clear by the pictures of the disassembled Alumitone, do the patent drawings illustrate the unseen feature you're referring to? Just so it is known, the patent does say explicitly that the inventor believes the "8" figure induces hum cancelling: "It should be appreciated that the shape of the primary winding 320 produces a hum canceling effect due to the current flow therethrough." Normal hum bucker sized version: There are two loops that share a common leg. A hum field causes a changing flux through both loops, and thus induces voltages around both loops. The idea is indeed just like a standard humbucker: the voltages are added out of phase by using the appropriate electrical phasing. Magnets are placed so that each string induces voltage around each loop, and the magnets have opposite polarity so that the signals add rather than cancel. The loops complete by passing around the transformer core. This is the primary winding. The core must have a high enough permeability so that the primary has enough inductance to allow the voltage to develop at all guitar frequencies. The very high turns ratio means that the required much higher voltage can develop at the secondary. (I think that there should be a piece of the transformer core that connects the two core ends together, put on after the core ends are placed through the loop. This would complete the flux path around the transformer and greatly increase the inductance. Otherwise there is a huge gap. Is such score piece part of the construction? If so, then one one can be sure there is one transformer. Otherwise, you could look at it as two transformers with some coupling between them.) "Since the phases of EMI cancels out at any point along the center leg..." I do not understand this. I do not see how this relates to voltages induced around a path by changing flux through the path. The single coil wide version: It appears to be the analog of two coil humbuckers where one coil is used for three strings, the other for the other three strings. Or two and two for the more familiar bass pickup. This interpretation requires that there be two loops, one for the three strings further from the transformer, and the other for the strings further away. I have identified the loop path for the strings further away. I do not see why you say there are not two loops, if that is what you mean, I might be misunderstanding. |
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Post by antigua on Dec 5, 2016 22:47:23 GMT -5
I'm fairly confident that the smaller Lace Alumitones I have are merely miniature versions of the full side humbucker, but with half as much magnet. It's as if you were to arbitrarily pull some slugs and screws out of a PAF, or the Seymour Duncan Vintage Rails, which in a very similar fashion, cut the blades short half way for no apparent reason (the black portion is plastic filler):  As the patent states: "It should further be appreciated that, if more than one permanent magnet 28 is used, the primary winding(s) 20 around each of the permanent magnets 28 may be connected in parallel or series."So the magnet layout is more arbitrary than anything. I emailed Tech@lacemusic.com earlier today, asking if the primary, secondary, or both, were responsible for humbucking. I got a reply from Jeff Lace himself. It was very nice of him to take the time to reply:
"On all our Alumitone both the primary and secondary are humbucking. The dual pathways in the primary surrounding the magnets ( one for north magnet and one for a south magnet) provides humbucking. In the earliest version of this technology, we used a simple single loop for the primary. This version was known as the Transensor and was phased out in favor of the Alumitone which had the benefit of the humbucking primary, but also has a more radical look to highlight how different it is. We’ve done some versions in both copper and aluminum for the primary, and have found that not only the substantial weight reduction with aluminum, but it also had some unique tonal quality that are very useful." |
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Post by ms on Dec 6, 2016 10:21:38 GMT -5
I'm fairly confident that the smaller Lace Alumitones I have are merely miniature versions of the full side humbucker, but with half as much magnet. It's as if you were to arbitrarily pull some slugs and screws out of a PAF, or the Seymour Duncan Vintage Rails, which in a very similar fashion, cut the blades short half way for no apparent reason (the black portion is plastic filler): As the patent states: "It should further be appreciated that, if more than one permanent magnet 28 is used, the primary winding(s) 20 around each of the permanent magnets 28 may be connected in parallel or series."So the magnet layout is more arbitrary than anything. I emailed Tech@lacemusic.com earlier today, asking if the primary, secondary, or both, were responsible for humbucking. I got a reply from Jeff Lace himself. It was very nice of him to take the time to reply:
"On all our Alumitone both the primary and secondary are humbucking. The dual pathways in the primary surrounding the magnets ( one for north magnet and one for a south magnet) provides humbucking. In the earliest version of this technology, we used a simple single loop for the primary. This version was known as the Transensor and was phased out in favor of the Alumitone which had the benefit of the humbucking primary, but also has a more radical look to highlight how different it is. We’ve done some versions in both copper and aluminum for the primary, and have found that not only the substantial weight reduction with aluminum, but it also had some unique tonal quality that are very useful."Well, I suppose with a many turn coil there is a clear distinction between the coil and the connecting wires, but not so much of a distinction with a single turn coil. However, to me it looks as though there is a clear intend to sense the strings further further from the transformer with a loop that occupies most of the width of the pickup, and then to conduct the signal to transformer with a pair of narrowly spaced conductors. That is, the conductors run by the loop for the strings closer to the transformer, limiting its width and thus setting the width for the loop further away so that they are the same. I think the the quote from the patent means that Lace thinks of the conductor surrounding a magnet as an individual loop. This is also how I interpret his statement in his response to you: that there is a separate pathway around each magnet, whether the magnets occupy the full length or half the length. |
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Post by ms on Dec 8, 2016 7:26:48 GMT -5
This picture (  ) is from here: www.amazon.com/Lace-21056-Alumitone-Single-Chrome/dp/B000Q4TZPG. It clearly shows that the transformer couples to the end of the pickup to two primary loops, not the center as you wrote. It also clearly shows the core completing around the end. This is done by interleaving multiple thin pieces into the core body rather than a single piece cap as I had guessed. There is a lot of talk on the web about how this is a current based pickup rather than voltage. No, it is just a very low voltage pickup with a huge voltage boost resulting from a high turns ratio transformer. |
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Post by reTrEaD on Dec 8, 2016 9:28:48 GMT -5
There is a lot of talk on the web about how this is a current based pickup rather than voltage. No, it is just a very low voltage pickup with a huge voltage boost resulting from a high turns ratio transformer. I'm not sure where the "No" comes from. It doesn't seem as though either description is at odds with the other. |
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Post by antigua on Dec 8, 2016 12:52:36 GMT -5
I think they say it's "current based" because it generates greater current in trade for the low voltage. Jeff Lace said in that response that the aluminum produced a "unique tonal quality" over a copper version, so maybe they believe that having a low voltage/high current has some tonal consequences, though I agree, it seems to be a novelty from an electrical standpoint. I think the more interesting thing is that you can shape a single chunk of aluminum or copper in way that traditional coil can't be, though the way this piece of aluminum is shaped, I wouldn't expect it to perform much different from a traditional coil, other than the fact that it has much less depth to it.
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Post by ms on Dec 8, 2016 12:56:08 GMT -5
There is a lot of talk on the web about how this is a current based pickup rather than voltage. No, it is just a very low voltage pickup with a huge voltage boost resulting from a high turns ratio transformer. I'm not sure where the "No" comes from. It doesn't seem as though either description is at odds with the other. It comes right from the physics. The law of magnetic induction says that a voltage is generated around a path in response to magnetic flux through the path changing in time, not a current. This is true whether you have one turn of 10,000. Current flows as the result of a load on the pickup. With a very high impedance load, very little current flows. The voltage is then correspondingly close to what the law of induction alone predicts. Put a load on it and the voltage drops in a predictable way. The total rate of change of flux has changed because the current flowing in the load creates a flux that opposes the original. This is sometimes referred to Lenz's law, which is loosely translated as "There ain't no free lunch." |
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Post by antigua on Dec 8, 2016 13:03:45 GMT -5
So there isn't much current in the primary, due to the high impedance load on the other side of the transformer? My understanding was that a transformer basically traded current for voltage, and so the primary would need to provide a higher current, if you wanted a higher voltage to come out of the secondary.
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Post by reTrEaD on Dec 8, 2016 13:45:18 GMT -5
Absolutely true.
Yes, and to accurately predict the voltage (and current) you need to include the internal impedance as well as the impedance of the load.
Apparently your purist sensibilities are being offended by the term "current based". And perhaps rightfully so. But I interpret the intended meaning not to be suggesting a different mechanism for transferring energy but rather the inherent ability to supply much higher current due to the extremely low internal impedance.
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Post by reTrEaD on Dec 8, 2016 13:50:29 GMT -5
So there isn't much current in the primary, due to the high impedance load on the other side of the transformer? My understanding was that a transformer basically traded current for voltage, and so the primary would need to provide a higher current, if you wanted a higher voltage to come out of the secondary. I agree. And it goes back to the "no free lunch" reasoning. We can think of a transformer in much the same way as we think of a gearbox. Trading rotational speed for torque or vice-versa. |
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Post by ms on Dec 8, 2016 14:49:58 GMT -5
So there isn't much current in the primary, due to the high impedance load on the other side of the transformer? My understanding was that a transformer basically traded current for voltage, and so the primary would need to provide a higher current, if you wanted a higher voltage to come out of the secondary. Yes, the current in the primary is much higher than the secondary, just as the voltage is lower. Why point is that it is a voltage that is generated by the changing magnetic flux from the vibrating string, and that is equally true whether the pickup has one turn or many. What happens after that is analysis of the circuit. |
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Post by ms on Dec 8, 2016 15:04:41 GMT -5
Absolutely true. Yes, and to accurately predict the voltage (and current) you need to include the internal impedance as well as the impedance of the load. Apparently your purist sensibilities are being offended by the term "current based". And perhaps rightfully so. But I interpret the intended meaning not to be suggesting a different mechanism for transferring energy but rather the inherent ability to supply much higher current due to the extremely low internal impedance. Yes, but as you increase the load, you approach the voltage predicted by the law of magnetic induction. That law always works no matter how many turns you have. Sensibilities have nothing to do with it. Physics must be applied precisely or the wrong answer will be found. In any case a pure voltage source has zero internal impedance while a pure current source has infinite internal impedance. Thus one could argue this the other way around. It is better not to apply technical sounding things loosely except in advertising copy where the goal is to sell a product based on whatever BS you can come up with, or in a patent where once you have satisfied the examiner, the more confusing BS you can include, the harder it is for someone to duplicate what you did. |
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Post by reTrEaD on Dec 8, 2016 16:40:56 GMT -5
Better is always better but as they say ...
(sh)It happens.
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Post by antigua on Dec 8, 2016 23:45:53 GMT -5
It is wrong of Lace to imply that the Alumitone is in any way new technology. Based on their marketting and it's radical appearance, I had initially been tricked into thinking the pickup operated with fundamentally different principles than a typical pickup, when it is in fact a novel application of a low impedance pickup, which you could find in the Les Paul Recording Model, so many decades ago. But if you google "current driven" "voltage driven", it appears to be a thing to speak of low impedance and "current driven" interchangeably: www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=%22current+driven%22+%22voltage+driven%22 |
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Post by antigua on Dec 9, 2016 0:23:51 GMT -5
Here are some magnet film pics: Over the pickups:  Over the strings:  The dispersal at the strings looks a little wider at the strings than is seen with screws and slugs or pole pieces. |
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Post by ms on Dec 9, 2016 7:00:49 GMT -5
It is wrong of Lace to imply that the Alumitone is in any way new technology. Based on their marketting and it's radical appearance, I had initially been tricked into thinking the pickup operated with fundamentally different principles than a typical pickup, when it is in fact a novel application of a low impedance pickup, which you could find in the Les Paul Recording Model, so many decades ago. But if you google "current driven" "voltage driven", it appears to be a thing to speak of low impedance and "current driven" interchangeably: www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=%22current+driven%22+%22voltage+driven%22Yes, those terms can be sensible when talking about how a source drives a load: if the impedance of the load is higher than the source impedance of the driver over the useful frequency range, then it is considered voltage driven. An example is most SS audio power amps, using emitter follower output stages and lots of global feedback. How about a guitar pickup driving pots, cable and amp? Consider a single coil Fender type pickup. Its source impedance might be under 10K at low frequencies, and you can think of it as driving a voltage into the load. But at the resonance, its source impedance is mostly inductive and interacts with the load, which is mostly capacitive, making an impedance higher in magnitude than either source or load impedances. It is a system, not a simple source driving a simple load. |
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Post by Yogi B on Dec 14, 2016 15:22:09 GMT -5
Jeff Lace said in that response that the aluminium produced a "unique tonal quality" over a copper version, so maybe they believe that having a low voltage/high current has some tonal consequences If Lace was striving for the highest possible current in the primary then we'd be discussing Silvetone pickups, but we're not. I think you can guess the next bit, but first lets also remind ourselves that Lace also stated aluminium offers "substantial weight reduction", yes it's about 3.3 times less dense than copper. Copper costs about 3 times more than aluminium by weight, thus if you wanted to make a copper version with the exact dimensions of the Alumitone the frame would be about 10 times more expensive in raw materials. Also this might be of interest: www.lacemusic.com/alumitone_article.php |
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Post by antigua on Dec 14, 2016 19:02:16 GMT -5
That article was painful to read.
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