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Post by stratotarts on May 29, 2017 15:55:44 GMT -5
If you wanted to go this way, one idea would be to use a plastic pickup cover, and adhesive copper tape, to try different slot configurations, instead of all that jeweler's saw/Dremel work. If only it were that easy. But I have seen in one circumstance that the tape doesn't behave at all like the brass sheet. I examined a humbucker where both coils were wrapped with the copper tape. Surprisingly it only made a few dB difference. From what I've seen with the covers, the same geometry in brass would produce a radical change. I cut the tape in place to prove this. My research was done with thick copper wire, which always conducts reliably. I believe the copper sheet is too thin.
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Post by stratotarts on May 29, 2017 8:20:41 GMT -5
I'm wondering about the string balance on your implementation. It's clear that the bulk response is transparent, but I'm worried about individual poles. The G string slot clearly has no conductive path, but from an individual pole point of view, the A string for example, does. It's possible for currents to travel in the side wall and circumvent the slot. I wonder if you could compare the G with the A using your small test coil to confirm or deny this?
I have one more brass cover to butcher, and it will be a while before I can get more. I want to make the next experiment count.
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Post by stratotarts on May 28, 2017 22:37:34 GMT -5
There's just one side cut. I also tried measuring the peak with only the side cut, and only the top slots (with another brass cover that is not pictured), and in both cases, the peak only increased by about 3dB. Two two cuts together caused it to shoot up 15dB, on par with no cover. That's really interesting and a little unexpected that not every slot needs to go all the way down. It certainly improves the mechanical strength compared with cuts all the way. Thinking about it, I guess it does meet the current path criterion. So I will think about possible changes to the half slot version I made:
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Post by stratotarts on May 6, 2017 8:18:36 GMT -5
Where are the magnets?
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Post by stratotarts on Apr 25, 2017 8:33:07 GMT -5
I have a question, does the frequency response of an amplifier vary with input voltage? Sort of. Due to slew rate limiting, the maximum signal amplitude decreases with increasing frequency. Because the useful area of operation of most amps is the linear region, this can be expressed as GBW (gain-bandwidth product). But real world amps like a guitar amp are designed so that the gain is adequate for the highest frequency. In that case, the maximum input level does not depend on frequency. Also within the specified operating limits, the input-output differential (gain) mainly does not depend on frequency unless there is equalization (such as tone circuitry). There will be some non-linearity in both the time and frequency domain due to the imperfections of real world components and circuits.
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Post by stratotarts on Apr 24, 2017 10:08:29 GMT -5
This is very frustrating, because it's always seemed to me (and a lot of other guitarists) that the tone changes with pickup height. I have to admit though, I don't hear much difference in the actual recordings, I mostly perceive a difference when I'm actually plugged into an amp, which gets me to thinking that this might have more to do with increasing voltage in front of amp, than anything relating to the pickups, so that might be where I look next for variation by pickup height. If the difference owes to "push", though, I should be able to duplicate any such difference with a booster. I performed a crude version of this experiment and posted on TDPRI a while back. I also didn't see much, or hear any difference. Basically I recorded samples and adjusted the volume to make them equal. Of course, an experiment with limitations produces accordingly limited results. But I think that you can at least say, the effects must be much more subtle than is commonly believed, because statements like "night and day difference" are often used. Sometimes people imply that it makes more difference than anything else. Since the effects of those "anything else" have been found to be clearly and easily measurable, the expectation that this aspect would also be obvious if it were that obvious seems reasonable. I think you are on the right track with the amplifier theory. The other thing that people might change when the pickup changes, is the guitar volume knob. We know that it makes a difference. I also think there must be some difference. So a refinement of the experiment could reveal the actual extent. To quantify it would help a lot to put the doubts to rest. I wish I had the time for it now.
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Post by stratotarts on Apr 2, 2017 17:51:51 GMT -5
I have some smaller electromagnets similar to this one: link . The ones I have are about 8mm in diameter so would fit over a string quite well. One way to get a giant pulse out of it is to charge a big cap and discharge it through the coil. They might be too slow even with a big pulse. Might destroy it trying to hit it hard enough. You might be able to do it with the low impedance side of a cheap audio transformer if you saw the core to make the best shaped field that you can. You would need to filter out the lows in order not to saturate it, but that might simulate the stretch and release of a pick. Another thing you could do, is energize the electromagnet with the rated 12V, manually push the string so it sticks to it, wait for the vibrations to settle down and then release it by turning off the 12V.
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Post by stratotarts on Apr 2, 2017 11:01:07 GMT -5
I have some smaller electromagnets similar to this one: link . The ones I have are about 8mm in diameter so would fit over a string quite well. One way to get a giant pulse out of it is to charge a big cap and discharge it through the coil.
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Post by stratotarts on Mar 30, 2017 21:02:31 GMT -5
The most standard external power is a phantom powered XLR - would that be so bad as a guitar cable? You could plug right into any mixing board. Or a mic preamp like this: link
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Post by stratotarts on Mar 30, 2017 18:26:18 GMT -5
I think the active/passive choice has a lot to do with the cost/benefit trade off. The active choice has other limiting factors besides the cost of the circuitry. There is the hassle of the mods to the guitar to accommodate it and also the battery. If it is a stock feature of the guitar, it adds cost. It also adds a maintenance overhead for the player, as they have to maintain the freshness of the battery and replace it when it fades. Then there is the aesthetic - it conflicts with the common preference for things traditional and "vintage". All this for real advantages that most players don't really understand and might not really need. It would be more attractive, at least to players with some technical interests, if it were possible to add a few more useful design features to the basic concept. In fact, I want to do this. The "rabbit hole" is where the features get out of control and start escalating the cost and maintenance overhead again. Such systems have already been marketed and have some remarkable abilities, but I think deviate from the basic guitar concept to a degree that it almost becomes a different instrument. I want to respect the intrinsic nature of the instrument while using active circuitry to improve the player's control options, at the same time as providing the already well known basic advantages such as indifference to cord length. The important thing is to hit a sweet spot where numerous and useful advantages can be had with the maximum simplicity and lowest cost.
Oh, and most importantly, as with all my projects so far, I want to share my work freely and openly. Free as in both "free beer" and "free speech".
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Post by stratotarts on Mar 30, 2017 8:43:22 GMT -5
The four wire method has another advantage - there are actually six potentially useful connections: 1. Series in phase 2. Series (one coil reversed) 3. top coil 4. bottom coil 5. Parallel in phase 6. Parallel (one coil reversed)
But some of these would likely be underwhelming.
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Post by stratotarts on Mar 30, 2017 8:26:53 GMT -5
The way I started thinking, was why not ground the tap and then use the other two connections to select between the two winds. The capacitance of the other coil is out of the circuit that way, but since they are wound in the same direction, the result is that one coil will be out of phase. So then I thought, okay, there is no way to solve that other than reversing the connection of the out of phase coil. But then you can't put them in series, so you need separate coils.
We see a lot of aspects of pickup patents that have some of these characteristics:
1) Have dubious technical merit - no proof of actual performance or effective operation (essentially cosmetics masquerading as technology) or 2) Subsequently not applied by the patent holder or 3) Don't meet the criteria of being non-obvious or 4) Do work in certain configurations but not for the stated reasons
It's impossible to know the actual level of sincerity behind the applications. We have seen that most designers in this industry are very self confident but very few have the actual engineering background that it would take to translate an idea into a sound patent. Perhaps in some cases, the applicants have been coached to inflate or confabulate claims in order to gain acceptance. But I suspect that the other factor, is an attempt to consolidate territory - to effectively block competition by raising the barrier just high enough to make it not worthwhile to risk an infringement with similar designs that actually do work, or utilize the method in some way that makes it actually effective. Look towards the larger companies that have a long term outlook and can actually afford it, for this.
I am not a lawyer, so I'm not sure if a patent could be challenged on the basis of disuse.
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Post by stratotarts on Mar 29, 2017 13:27:25 GMT -5
I was thinking about Antigua's observation that the unused portion of a tapped coil adds a huge capacitance when the tap is selected. One solution is to bring four wire out and disconnect the unused portion. I was thinking - what about winding them in the same direction, with one end of each coil made common and connected to ground, then the coils selected with the traditional two way selector switch? Would it be different enough from Gibson's patent on bifilar coils to be considered outside the scope of the patent?
Oh, wait - that does add extra wire. Never mind.
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Post by stratotarts on Mar 27, 2017 18:07:37 GMT -5
Yes, it's likely that the Ebow uses some kind of limiter circuit so that the oscillations don't become excessive and drive the string into a buzz. It could be a simple clipping circuit, or else it could be something that stays linear like a compressor.
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Post by stratotarts on Mar 27, 2017 14:50:29 GMT -5
I'm still digesting this. It's very compelling and has some interesting ramifications. Just one thing that bothers me - the Ebow works by feeding back the signal from the string, I think. So the output is affected by the signal it receives. That might be exaggerating the harmonic amplitudes by means of feedback. I think it would be preferable to drive the Ebow with a fixed frequency generator to highlight the proportions more exactly. Some aspects of the test are completely arbitrary, but the important thing is whether or not the arbitrary test answers any questions. The strength, position of and magnitude of effects are all arbitrary. What matters is that they happen, that there's an asymmetry that favors the side of the string with the magnetic pull, and more particularly, the harmonics whose anti nodes are most immediately within the pull of the magnet. That's a good point about the EBow being designed to reinforce it's input, and that might have a) led to some suppression of of the 2nd harmonic, since it's anti node is under the EBow, and b) caused over representation of the fundamental, since the EBow is over it's sole "anti node". As far as I can tell, there's not reason the EBow would help or hurt the overall weighting phenomena that's observed with the magnetic pull, since the EBow is centrally positioned along the string. Sure, mainly this would just affect the exact ratio of the amplitudes, what I suggest is just a small refinement. It raises a point... a pull at antinodes has an effect of increasing some harmonics, yet the antinodes are exactly the places where some harmonics are suppressed in the output ... this means that there are some very complicated relationships to explore.
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Post by stratotarts on Mar 27, 2017 8:43:21 GMT -5
I'm still digesting this. It's very compelling and has some interesting ramifications. Just one thing that bothers me - the Ebow works by feeding back the signal from the string, I think. So the output is affected by the signal it receives. That might be exaggerating the harmonic amplitudes by means of feedback. I think it would be preferable to drive the Ebow with a fixed frequency generator to highlight the proportions more exactly.
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Post by stratotarts on Mar 25, 2017 7:30:28 GMT -5
The magnet can't damp the vibration, exactly. The amount of energy gained as the string approaches the magnet is equal to the amount of energy lost as it moves away. But the harmonics are waves that are controlled by the location of fixed points in the string because they act as reflectors - normally the endpoints. As the force resulting from the magnetic field approaches the force due to the displacement of the strings elasticity, the magnet becomes a fulcrum that reflects some of the displacement energy back into the string. This causes the normal harmonics to be translated to new harmonics that are related to the distances between the magnet and the fixed end points. Since the fulcrum is "soft", they don't maintain themselves, but rely on continuing excitation from the string.
Theory based on general physics - of course it's up for debate and testing. Actually a good way would be to look for the translated harmonics in a spectral plot. I guess this is a different topic though, perhaps deserves another thread if it needs further explication.
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Post by stratotarts on Mar 20, 2017 16:08:01 GMT -5
Would not signals induced by the alternating field in the return path, be in some fixed phase relationship to the signals induced by the alternating field in the main path? If that is the case, only the overall amplitude of the signal will be affected by any portions of the coil that intersect the return path. Since, the string is always in a fixed position relative to any part of the coil winding. If there is no phase shift, there is no group delay.
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Post by stratotarts on Mar 20, 2017 15:02:13 GMT -5
If you want to get into the HiFi voodoo jargon that you probably won't like, one phenomenon is referred to as group delay. No, group delay is a common engineering term. Wiki link
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Post by stratotarts on Mar 20, 2017 14:28:12 GMT -5
I told you you wouldn't like it. There is nothing to like or dislike. You haven't really presented anything that has any meaning. I wasn't going to say it, but since you persist - it is very obvious that your knowledge of physics and electronics is rather limited. That in itself is nothing, but you're pretending otherwise.
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Post by stratotarts on Mar 20, 2017 14:15:46 GMT -5
Furthermore, to have comb filtering you need signal inversion - all the induced voltages in a coil are in-phase.
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Post by stratotarts on Mar 19, 2017 20:28:47 GMT -5
There are many simple ways of constructing a higher frequency pickup system. The simplest is to use the parallel configuration of a humbucker. Actually, you could use a high impedance preamp with a suitably chosen resistive load, and get an almost flat response up to the unloaded resonant peak of most existing pickups. That would get you up to 10k without breaking a sweat. A low impedance, low inductance coil can also get you there. But when you look at sonic preferences, most players dislike the tone of high fidelity (high frequency) pickups. For example, everyone raves about the Cavalier Lion. Well the frequency response is one of the lowest of any Tele bridge out there.
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Post by stratotarts on Mar 19, 2017 15:18:04 GMT -5
I think it makes sense that the sensing area is smaller for steel poles vs. alnico. The fact that the permeability is much greater means that the field will tend to concentrate more towards the center of the pole. More puzzling is the result that that staggered pole resulted in a wider field. That is strange.
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Post by stratotarts on Mar 18, 2017 21:19:37 GMT -5
Frank, I believe that when there are flaws in the reasoning or experimentation that appears here, we are very open to having them pointed out. But it's not fair, or good science, to expect any opinions to change without presenting any concrete arguments or data. In fact, most of us have had a few occasions of being in need of correction. It is healthy. I like this forum a lot because of the gracious exchange of criticism. However, it has become almost an unwritten law here that arguments and theories need objective support. In this matter, there is a fundamental incompatibility between proprietary, private research and the open, public exchange that goes on here. I think it is because of the skeptical scientific background that many of us here have. You may consider our efforts amateurish - it is your right to an opinion. However, it doesn't carry much weight when you are unwilling to clearly demonstrate the basic facts of your own efforts here. To flaunt them and refuse to back them up simultaneously, is a contradictory behaviour that benefits nobody.
I have no automatic respect for R+D teams and expensive equipment. Of course they're wonderful. But they don't gain you any more academic or actual credibility in of themselves. It's how they are used that is potentially powerful. In fact, when they're convoluted with strong pecuniary interests and strong egos, they frequently steer the ship of truth off course. Think Pons and Fleichmann. Or many drug manufacturer funded product safety studies. Or the lunatic fringe - the free energy folks and so on. What they mainly lack is transparency and a healthy balance of competitiveness and information sharing. Also a healthy respect for the need for rigorous, thoughtful and well designed experimental procedures to support theory.
So, if you have specific criticisms against any of our thinking or procedure, the appropriate response is to respond with scientific data in the common vernacular of engineering, not rhetorical gestures or synthesized jargon that only you possess the full meaning of. Some of your comments in this thread border on insulting. You should consider how that affects your public image if you are in this as a career.
Edit - also you make reference in several places to listening tests. These are notoriously susceptible to psychological biases, and have no credibility unless a tight regime of safeguards are employed. Unless you can assure us that these were randomized, double blind tests with a sufficient sample size to be statistically valid, it would be foolish to pay any attention because of the long history of inattention to these important factors in this field.
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Post by stratotarts on Mar 18, 2017 8:49:22 GMT -5
Then why doesn't every guitar amp and/or pedal begin with a 5K brick wall filter? Or 10K even? If those frequencies are meaningless why are they allowed? If you ignore 5-25kHz your conclusions suffer. If you promulgate it you're guilty of the same misleading propaganda the likes of which you've accused the marketing charlatans and profiteers. As for the return path, that meter isn't going to tell you anything about it. If something is to small to matter, why would you go to the trouble of filtering it out? Consider 15KHz. To get it down to 3KHz to have to intermod it with 12KHz or 18KHz. Both terms of the product are small in either case, and so the resulting product is doubly small. I think these products are insignificant. I agree. There are some good characteristics of amplifiers that are merely fortuitous. Their presence doesn't imply a necessity for all the advantages they yield. It would be a good idea for Falbo to present some experimental data to support his claims. He hasen't yet explained how he arrived at his conclusions about the 5-25Khz signals. Theorizing is great for establishing new directions and uncovering clues. But without verification, there is too high a risk of delusion or running in circles.
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Post by stratotarts on Mar 15, 2017 21:28:00 GMT -5
I would expect the window to get smaller as the distance between the string and the pole piece decreases. The field diverges as it gets further away from the pole. But that is not the whole story. If you have a pole piece of diameter D, and you are looking significantly closer to it than D, I would expect the window to change slowly, but as you get further away it should change more quickly. All magnetic sources look like dipoles if you get far enough away, but up close it is different. Consider the field of a solenoid (http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/solenoid.html). Inside the solenoid the field is uniform, but as the lines come out an end, they diverge, but right outside they are nearly straight, especially near the center of an end. (The field strength is proportional to the density of lines.) Yes, and since the string to pole distance is nearly equal to the pole diameter, the window difference due to the former ought not to be very much.
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Post by stratotarts on Mar 15, 2017 18:46:29 GMT -5
I would expect the window to get smaller as the distance between the string and the pole piece decreases. The field diverges as it gets further away from the pole.
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Post by stratotarts on Feb 28, 2017 10:28:58 GMT -5
In fact, I am considering getting into pickup manufacturing. I want to collaborate with a woodworker friend to build complete guitars. So I am thinking of trying to integrate all the neat stuff that we've learned. I want to toss out almost everything traditional and start from scratch.
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Post by stratotarts on Jan 14, 2017 19:12:36 GMT -5
Nice, really nice. I think you mean Loaded Res. Freq. (kHz) w/470pF, not Loaded Res. Freq. (pF) w/470pF.
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Post by stratotarts on Jan 8, 2017 9:09:43 GMT -5
Maybe the slot modification would help.
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